Chapter 3 Avena Igor G. Loskutov and Howard W. Rines Devoted to Ken Frey – Oat Breeder 3.1 Introduction Oat is one of the most important cereal crops in the world. The genus Avena L. includes cultivated species with different ploidy levels and a number of wild species reflecting a wide range of botanical and ecological diversity. A majority of these forms came from the centers of origin, which by definition shows great diversity of Avena species. With this in view, oat species became the subject of investigations to specify the complex organization of the Avena genus and indicate aspects of its evolution and phylogenetic links between the species. Further search for agronomical traits and utilization of new oat breeding sources is very important for breeding purposes. 3.1.1 Basic Botany of the Species 3.1.1.1 Taxonomic Position of Avena Species Investigation of species diversity using morphological traits is very important for their systematization and determining taxonomic position. Taxonomic and morphological descriptions of species of the genus Avena L. was started as far back as the sixteenth century (Tournefort 1700) and continues till today. A great number of species had been described by a number of authors since establishment of the system of binary I.G. Loskutov (*) Department of Genetic Resources of Oat, Barley, Rye, N.I. Vavilov Institute of Plant Industry, 44, Bolshaya Morskaya Street, St. Petersburg 190000, Russia e-mail: i.loskutov@vir.nw.ru nomenclature proposed by C. Linnaeus (Linneaus 1753) (Table 3.1). In most cases, characterization of a species was initially performed on the basis of morphological traits. An example of one of the first descriptions of the diploid species is the characterization of cultivated Avena strigosa (Schreber 1771). Later, this species was described as A. hispanica Ard. (Malzev 1930). Another wild diploid species A. pilosa was first described during examination of the material collected in the Transcaucasus (Marshall Bieberstein 1819). During processing of the Algerian materials, the same species was described under the name A. eriantha Durieu. Another original species was described under the name A. clauda (Durieu de Maisonneuve 1845). These two species are morphologically similar: the only distinction is that A. clauda disarticulates single florets instead of spikelets, like A. pilosa, due to the presence of a callus only in the lowest floret, governed by one or two genes (Rajhathy and Thomas 1967). According to the opinion supported by Malzev (1930), disarticulation of spikelets is an advanced way of seed distribution. With the help of two awns in a spikelet, seeds can move and twist into the soil surface more efficiently than with only one awn of a single floret. Moreover, with a spikelet, several seeds, instead of just one, bury into the soil simultaneously. There are two more closely related species, one described under the name of A. ventricosa (Balansa 1854) and the other as A. bruhnsiana (Gruner 1867). Along with morphological and physiological similarities, and thanks to the elongated callus, their seeds can screw into the toughest stony soil even under the strongest drought in the steppe, deserted areas, or on ranges. Along with the above-mentioned species, A. longiglumis was initially described by the author in the course of processing the materials from Algeria C. Kole (ed.), Wild Crop Relatives: Genomic and Breeding Resources, Cereals, DOI 10.1007/978-3-642-14228-4_3, # Springer-Verlag Berlin Heidelberg 2010 I.G. Loskutov and H.W. Rines Table 3.1 The history of description Avena species Species Ploidy A. fatua L. 6 A. sativa L. 6 A. sterilis L. 6 A. strigosa Schreb. 2 A. barbata Pott ex Link 4 A. hirtula Lag. 2 A. pilosa M. Bieb. 2 A. clauda Durieu 2 A. longiglumis Durieu 2 A. occidentalis Durieu 6 A. byzantina C. Koch 6 A. abyssinica Hochst. 4 A. macrostachya Balansa et Durieu 4 A. ventricosa Balansa 2 A. wiestii Steud. 2 A. ludoviciana Durieu 6 A. bruhnsiana Gruner 2 A. vaviloviana (Malz.) Mordv. 4 A. magna Murphy et Terrell 4 A. murphyi Ladizinsky 4 A. prostrata Ladizinsky 2 A. damascena Rajhathy et Baum 2 A. canariensis Baum, Raihathy et Sampson. 2 A. atlantica Baum et Fedak 2 A. agadiriana Baum et Fedak 4 A. insularis Ladizinsky 4 Year of description 1753 1753 1762 1771 1799 1816 1819 1845 1845 1845 1848 1851 1854 1854 1855 1855 1867 1927 1964 1971 1971 1972 1973 1985 1985 1996 (Durieu de Maisonneuve 1845). According to Malzev (1930), all the mentioned species are primitive ones, and this view was later supported by other researchers (Rajhathy and Thomas 1974). The diploid oat A. prostrata was described during exploration of the southwestern coast of Spain by a collecting mission. The most typical characters of the species are the minimal size and some other traits related to the grains as well as the prostrate juvenile growth of the plant (Ladizinsky 1971b). The species A. damascena, characterized by the semi-prostrate juvenile growth, was described for the first time during an expedition to the Syrian territory (Rajhathy and Baum 1972). The diploid species A. canariensis collected on Fuerteventura Island (Spain, the Canaries) disarticulates spikelets and has bidentate lemma tips (Baum et al. 1973), the latter trait not characteristic of the diploid species. The lodicules and epiblast of the species are of the hexaploid cultivated type, though it is not characteristic in all of the diploid species. A. wiestii was described on the basis of seed samples and herbarium materials collected in Egypt (Steudel von Reference Linneaus (1753) Linneaus (1753) Linneaus (1762) Schreber (1771) Pott (1799) Lagasca (1816) Marshall Bieberstein (1819) Durieu de Maisonneuve (1845) Durieu de Maisonneuve (1845) Durieu de Maisonneuve (1845) Koch (1848) Hochstetter (1852) Balansa and Durieu Maisonneuve (1854) Balansa (1854) Steudel von (1855) Cosson and Durie de Maisonneuve (1855) Gruner (1867) Malzev (1930) Rajhathy et al. (1966) Ladizinsky (1971a) Ladizinsky (1971b) Rajhathy and Baum (1972) Baum et al. (1973) Baum and Fedak (1985a) Baum and Fedak (1985b) Ladizinsky (1998) 1855). The species A. hirtula was initially described in Spain (Lagasca 1816) and A. atlantica – during a collecting mission to the Atlantic coast of Morocco (Baum and Fedak 1985a). Morphologically, the latter species is similar to A. hirtula, with the only difference that A. atlantica disarticulates spikelets instead of single florets. The tetraploid species A. barbata was initially described in Portuguese material (Pott 1799). Later, this species was described as A. hirsuta Roth (Malzev 1930), though according to Baum (1977), A. hirsuta is a synonym of A. matritensis Baum. Romero Zarco (1990) subdivides A. barbata into A. barbata subsp. barbata proper and A. barbata subsp. lusitanica, while Baum (1977) assigns the species rank to the latter subspecies and proposes the diploid species A. lusitanica Baum. The ploidy level of the latter species has been questioned recently (Markhand and Leggett 1996). The species A. vaviloviana has been found by Vavilov (1965b) in Ethiopia and initially described as a subspecies of A. strigosa subsp. vaviloviana Malz., but later it was promoted to a species level 3 Avena (Mordvinkina 1936). Malzev (1930) believed this species to be a wild parent form of A. abyssinica (Hochstetter 1852) with which it shared the same natural habitat that differed from that of other tetraploid species. According to Vavilov, the African group of oats, studied by Trabut (1909), had to be subjected to a special study, as there was no reason for uniting it with the European and Asian species (Vavilov 1965a). At present, this group of species is considered independent from the others (Baum 1977; Loskutov 2008). The tetraploid species A. agadiriana was first described from the material collected in Morocco on the Atlantic and Mediterranean coasts. Morphologically, this species resembles A. barbata (Baum and Fedak 1985b), but it sharply differs in that A. agadiriana disarticulate spikelets and bidentate lemma tips. The species A. magna was described during explorations of the Mediterranean coast in Morocco (Rajhathy et al. 1966). It is believed that this species had been initially described as A. moroccana Gdgr.; however, no direct proof of that has been found. The discovery of A. magna has “filled the last cell” concerning traits homology in the tetraploid species, as it was the species with only the first lower floret to have a callus. This type of joint had been previously described only for the diploid and hexaploid species. Another species, A. murphyi, has been discovered and described from southern Spain (Ladizinsky 1971a). A series of morphological traits makes this species similar to A. magna, and therefore it was attributed to the Pachycarpa Baum section (Baum 1977) characterized by bidentate lemma tips. The species A. insularis was discovered and described in Italy, on Sicily. Morphologically, it occupies an intermediate position between A. murphyi and A. sterilis (Ladizinsky 1998). The outcrossing tetraploid perennial species A. macrostachya was discovered and described in Algeria (Balansa and Durieu de Maisonneuve 1854), though it is believed that initially it had been described under the name of Helictotrichon macrostachyum Holub (Holub 1958). Many researchers, due to morphological characteristics, regarded this species as a primitive representative of the genus Avena (Malzev 1930; Baum and Rajhathy 1976; Baum 1977; Loskutov 2007). Although the hexaploid A. fatua was one of the first described species (Linneaus 1753), a unified hypothesis has not been developed yet on the origin of this species regardless of the magnitude of research. The difficulty in identifying the progenitor of this species relates to its very wide polymorphism, which, according to Vavilov, is linked with its natural broad habitat (Vavilov 1965a). The species A. occidentalis has been described in the Algerian materials (Durieu de Maisonneuve 1845). This species greatly resembles A. fatua but has some differences concerning disease resistance and vegetative period duration. Other wild (A. sterilis – Linneaus 1762 and A. ludoviciana – Cosson and Durie de Maisonneuve 1855) and cultivated (A. sativa – Linneaus 1753 and A. byzantina – Koch 1848) hexaploid species have been described long ago and a broad spectrum of subsequent research has been devoted to their taxonomic affinity (Malzev 1930; Rajhathy and Thomas 1974; Baum 1977; Loskutov 2007). Thus, the taxonomic position of Avena species is not always unambiguous. In recent years, numerous collecting missions targeted on oat species have been carried out with new species being subjected to thorough investigation. 3.1.1.2 Geographical Locations of Genetic Diversity and Morphology of Avena Wild Species Natural and ecological conditions under which oat species grow differ considerably in terms of rainfall, temperature regime, altitude, and soil and subsoil types. The richest occurrence and highest genetic diversity of wild oat species in the Old World is observed in a narrow territory between latitude 20 and 40 N. It stretches mainly through basins of the Mediterranean, Black, and Caspian seas with very diverse ecological conditions. Morphological traits used for oat species characterization relate to the vegetative part of a plant; however, the main taxonomic characters are the detailed morphological features related to the structure of generative organs. Diploid Species Avena clauda Durieu, 1845, Rev. Bot., 1: 360, excl. syn.; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 111, t. 41, f. 2; Steud., 1855, Syn. Pl. gram., 1: 234; Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6: 42, 45; idem, 1899, I.G. Loskutov and H.W. Rines Mittel. Thur. bot., XIII, XIV: 47, excl. var. solida Hausskn.; Batt. et Trabut, 1895, Fl. Alger. Monocot.: 180; idem. 1902, Fl. anal. Alger.: 370; Malzev 1930, Ovs. & Ov.,: 230; Roshevitz 1934, Fl. USSR, II: 260; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 242; Rodionova et al. 1994, Cult. Fl.,: 100–102. Annual. Juvenile growth prostrate to semi-prostrate. Flowering stem erect, 60–100 cm high. Panicum unilateral. Spikelets awned, and containing 3–5 florets. Glumes very unequal, lower glume one-half of upper one with 7 veins. Lemma tips biaristulate to bisubulate. All florets disarticulate at maturity. Awn inserted at 1/3 of the lemma. Lemmas small or medium sized, glabrous, or pubescent; pubescence of white color. Callus elongated, linear, about 3 mm long. A. clauda can be found together with A. pilosa. It grows in Bulgaria, Greece, throughout Asia Minor, in Turkish, Iranian, and Iraqi Kurdistan, in Uzbekistan, Azerbaijan, high-altitudinal areas of Jordan, in Israel, Lebanon, Syria, Algeria, and Morocco. The species grows under conditions of the steppe climate with up to 350–500 mm annual rainfall, in mountainous semideserts and deserts, on coastal sands, on gray-brown, gray-meadow, alluvial meadow, chestnut and podzolic black soils, as well as on brownish and yellowishbrown stony soils (Malzev 1930; Roshevitz 1934; Ladizinsky 1971c; Baum et al. 1972a; Baum 1977; Kanan and Jaradat 1996; Leggett et al. 1992; Sheidai et al. 2002; Loskutov 2007). Avena pilosa M.Bieb., 1819, Fl. Taur.-cauc., III Suppl.: 84; Griseb., 1844, Spicil. Fl. rumel.: 452; Koch C., 1848, in Linnaea, XXI: 392; Ledeb., 1853, Fl. Ross., 4: 413; Steud., 1855, Syn. Pl. gram.: 231; Coss. et Durieu, 1855, Expl. Sc. Alger., II: 109; Batt. et Trabut, 1895, Fl. Alger. Monocot.: 179; idem. 1902, Fl. anal. Alger.: 370; Malzev 1930, Ovs. & Ov.,: 233; Roshevitz 1934, Fl. USSR, II: 261; Rodionova et al. 1994, Cult. Fl.,: 102–105. – A. eriantha Durieu, 1845, Rev. Bot., 1: 360; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 109; Nevski 1934, Work. Asie. Univ., ser. 8в, 17: 3; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 243; Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. clauda var. solida Hausskn., 1885, Mitt. geogr. Ges., 3: 237–239. Annual. Juvenile growth prostrate to semi-prostrate. Flowering stems erect, 55–85 cm high. Panicle unilateral. Spikelets awned medium sized and containing 2–3 florets. Glumes very unequal, lower glume one- half of upper one with 7 veins. Glumes medium sized, glabrous, or pubescent; pubescence of white color. Lemma tips biaristulate to bisubulate. Only the lower floret disarticulates at maturity. Awn inserted at 1/2 of the lemma. Callus linear elongated, about 3–4 mm long. A. pilosa (syn. A. eriantha Durieu) is usually found in a mixture with A. clauda. It occurs in Spain, Greece, Bulgaria, Ukraine (Crimea), Russia (Dagestan), Iranian, Turkish and Iraqi Kurdistan, Uzbekistan, Azerbaijan, Turkmenistan, Morocco, Algeria, Lebanon, Syria, Jordan, and Israel. It grows on poor soils, e.g., gray-brown, gray-meadow, alluvial meadow, chestnut and podzolic black soils, as well as on limestone slopes, stony gray soils and on pebbly heavy loamy soils (Baum 1977; Baum et al. 1972a; Kanan and Jaradat 1996; Ladizinsky 1971c; Leggett et al. 1992; Malzev 1930; Musaev et al. 1976; Romero Zarco 1996; Roshevitz 1934; Sheidai et al. 2002). Avena ventricosa Balansa. ex Coss., 1854, Bull. Soc. Bot. Franc., 1: 14; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 109; Malzev 1930, Ovs. & Ov.,: 240, excl. subsp. bruhnsiana (Grun.) Malz.; Ladiz. et Zohary, 1971, Euphyt.,: 385–387; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 243; Rodionova et al. 1994, Cult. Fl.,: 110. Annual. Juvenile growth prostrate. Flowering stems erect, about 65 cm high. Panicle unilateral. Spikelets awned medium sized, and containing 2 florets. Glumes nearly unequal, about 27–30 mm long with 7 veins. Lemmas small sized, glabrous. Lemma tips bisubulate. Only the lower floret disarticulates at maturity. Awn inserted at 1/2 of the lemma. Callus very long awl-shaped, about 5 mm. A. ventricosa occurs on Cyprus as an adventive species. The primary focus of its distribution is located in Algeria and the secondary one, according to the unconfirmed reports, in Iran. Its typical habitats are stony soils with a surface of hard loamy crust, as well as a range of soils from limy to sandy desert ones (Malzev 1930; Bor 1968; Musaev and Isaev 1971; Baum et al. 1972a). Avena bruhnsiana Gruner 1867, Bull. Soc. Nat. Moscou, 40, 4: 458, t. IXB; Roshevitz 1934, Fl. USSR, II: 261; Musaev et Isaev, 1971, Work. AN AzSSR, 27: 64–65; Rodinova et al., 1994, Cult. Fl.,: 111. – A. ventricosa subsp. bruhnsiana (Grun.) Malz., 1930, Ovs & Ov.: 242. 3 Avena Annual. Juvenile growth prostrate. Flowering stems erect, 70–110 cm high. Panicle unilateral. Spikelets awned medium sized and containing 2 florets. Glumes nearly unequal, about 40 mm long with 7 veins. Lemmas medium sized, pubescent; pubescence of white color. Lemma tips bisubulate. Only the lower floret disarticulates at maturity. Awn inserted at 1/2 of the lemma. Callus awl-shaped very long, about 10 mm. A. bruhnsiana is an endemic species that used to grow in abundance throughout the Apsheron Peninsula in Azerbaijan in dry sandy and loamy places. At present, this species can evidently be found only in its northeastern part near the coastal sands on gray-brown soils (Malzev 1930; Roshevitz 1934; Musaev 1969; Musaev and Isaev 1971; Loskutov 2007). Avena longiglumis Durieu., 1845, Rev, Bot., 1: 359; Coss. et Durieu, 1855, Expl. Sc. Alger., 2: 110; Steud., 1855, Syn. Pl. gram.: 233; Batt. et Trabut, 1895, Fl. Alger. Monocot.: 179; idem. 1902, Fl. anal. Alger.: 370; Malzev 1930, Ovs & Ov.,: 238; Ladiz. et Zohary, 1971, Euphyt.,: 385–387; Baum 1974, Canad. Jour. Bot., 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 113–115 Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. barbata var. longiglumis Hausskn., 1899, Mittel. Thur. bot., XIII, XIV: 48. Annual. Juvenile growth semi-erect to prostrate with nodes covered by hairs. Flowering stems erect, 50–180 cm high. Panicle unilateral to equilateral. Spikelets large and containing 2–3 florets. Glumes nearly unequal, much longer than lemmas, 40 mm long with 9–10 veins. Lemmas large, pubescent, nearly equal. All florets awned. Lemma tips biaristulate 12 mm long. All florets disarticulate at maturity. Awn inserted at 1/2 of the lemma. Callus very long awl-shaped, about 10 mm. A. longiglumis can be found in the western Mediterranean, southern Spain, Portugal, Greece, Italy, Syria, Libya, Morocco, Algeria, Israel, and Jordan. This species grows on more dense substrates, on neutral red sandy soils, and prefers light sandy soils with a varying moisture content – from fertile coastal to poor sandy desert soils (Malzev 1930; Ladizinsky 1971c; Baum et al. 1972a; Rajhathy and Thomas 1974; Leggett et al. 1992; Kanan and Jaradat 1996; Romero Zarco 1996; Perez de la Vega et al. 1998). Avena damascena Rajhathy and Baum 1972, Canad. Jour. Genet., 14: 645–654; 1989, Rep. Work. Gr. Avena,: 19–32; Rodionova et al. 1994, Cult. Fl.,: 115. Annual. Juvenile growth prostrate. Flowering stem geniculate, 70–80 cm high. Panicle equilateral. Spikelets awned small and containing 3 florets. Glumes equal, about 20 mm long with 7 veins. Lemma tips biaristulate. All florets disarticulate at maturity. Awn inserted at lower 1/3 of the lemma. Callus roundedelliptical. A. damascena was first discovered in Syria and then in Morocco. The species grows under dry stony desert conditions on alluvial-pebbly grounds as well as on red-brown dry loamy sands within the 700–1,650 m altitudinal range (Rajhathy and Baum 1972; Baum 1977; Leggett et al. 1992). Avena prostrata Ladizinsky, 1971, Israel Jour. Bot., 20: 297–301; Baum 1974, Canad. Jour. Bot., 52: 2243; 1989. Annual. Juvenile growth prostrate. Flowering stem geniculate, 50–60 cm high. Panicle unilateral. Spikelets awned small and containing 2–3 florets. Glumes equal, 12–15 mm long with 9–10 veins. Lemmas small, pubescent. Lemma tips biaristulate. All florets disarticulate at maturity. Awn inserted at lower 1/3 of the lemma. Callus rounded. A. prostrata was discovered on the southwestern coast of Spain on poor loess deposits on limy and metamorphic rocks as well as in stony habitats. Also, the species has been found in the coastal part of Morocco on fertile red-brown soils (Ladizinsky 1971b; Leggett et al. 1992). Avena canariensis Baum, Raihathy et Sampson, 1973, Canad. Jour. Bot., 51, 4: 759–762; Ladiz., 1989, Rep. Work. Gr. Avena,: 19–32; Rodionova et al. 1994, Cult. Fl.,: 116. Annual. Juvenile growth prostrate. Flowering stems erect, 50–75 cm high. Panicum unilateral. Spikelets awned small and containing 2–3 florets. Glumes equal, 18–20 mm long with 9–10 veins. Lemmas small, pubescent. Lemma tips bidentate. Only the lower floret disarticulates at maturity. Awn inserted at 1/2 of the lemma. Callus elliptic. A. canariensis is an endemic species from the Canary Islands (Spain), where it occurs on Fuerteventura and Lanzarote islands. It grows within the 200–500 m range on piles of basalt stones, volcanic ash, or well-structured dry volcanic soils (Baum et al. 1973; Baum 1977). Avena wiestii Steud., 1855, Syn. Pl. gram.: 231; Roshevitz 1934, Fl. USSR, II: 265; Mordvinkina 1936, Cult. Fl. USSR,: 423; Baum 1974, Canad. Jour. Bot., I.G. Loskutov and H.W. Rines 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 105–108. – A. barbata var. caspica Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6: 41, 45. – A. strigosa subsp. wiestii (Steud.) Thell., 1911, Veirt. Natur. Ges., LVI: 333; idem, 1928, Rec. trav. bot. neer., XXVa: 435; Malzev 1930, Ovs. & Ov.,: 276; Ladiz. et Zohary, 1971, Euphyt.,: 385–387. – A. barbata subsp. wiestii (Steud.) Mansf., 1959, Kulturpflanze Beih., 2: 479; Tzvelev, 1976, Poaceae USSR,: 242; Romero Zarco 1996, Lagascal., 18, 2: 171–198. Annual. Juvenile growth semi-erect to prostrate. Flowering stems erect, 75–140 cm high. Panicle equilateral. Spikelets awned small and containing 2 florets. Glumes nearly equal, 10–20 mm long with 7–9 veins. Lemma tips biaristulate 3–6 mm long with 2 denticula. All florets disarticulate at maturity. Awn inserted at lower 1/3 of the lemma. Callus oval, about 2 mm long. A. wiestii can most often be found in Spain, eastern Transcaucasia, Azerbaijan, Turkey, Iraq, Iran, Syria, Jordan, Israel, Algeria, Egypt, in northern Sahara, and in the Arabian Peninsula. The species grows in the arid zone with 50–250 mm annual rainfall on sandy loess soils, limy slopes, gray-brown, gray-meadow and alluvial meadow soils, as well as on loamy sands in deserts and volcanic soils (Malzev 1930; Roshevitz 1934; Baum et al. 1972a; Romero Zarco 1984, 1996; Loskutov 2007). Avena hirtula Lag., 1816, Gen. Sp. Nov.: 4; Steud., 1855, Syn. Pl. gram.: 230; Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6: 42; Mordvinkina 1936, Cult. Fl. USSR,: 432; Baum 1974, Canad. Jour. Bot., 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 108–110. – A. lagascae Sennen, 1926, Pl. Esp.: 5980. – A. strigosa subsp. hirtula (Lagas.) Malz., 1930, Ovs. & Ov.: 247; Ladiz. et Zohary, 1971, Euphyt.,: 385–387. – A. barbata subsp. hirtula (Lagas.) Tab. Mor., 1939, Bot. Soc. Brot., ser. 2, 13: 622; Mansfeld., 1959, Kulturpflanze Beih., 2: 479; Romero Zarco 1996, Lagascal., 18, 2: 171–198. Annual. Juvenile growth semi-erect to prostrate. Flowering stems erect, 70–150 cm high. Panicle equilateral. Spikelets awned small and containing 2–3 florets. Glumes nearly unequal, 10–20 mm long with 7–9 veins. Lemmas equal, small or medium sized, strongly pubescent. Lemma tips biaristulate with 1 denticulum. All florets disarticulate at maturity. Awn inserted at lower 1/3 of the lemma. Callus narrow elliptic, about 2 mm long. A. hirtula with the highest degree of genetic polymorphism is observed in Spain, Portugal, France, Italy, and Greece. Besides, in the eastern Mediterranean, the species occurs in Algeria, Morocco, Tunisia, Israel, Turkey, Syria, and Jordan. Among its typical habitats are the areas with small-stony or limy soils and sand dunes (Vavilov 1965c; Rajhathy et al. 1966; Baum et al. 1972a; Baum 1977; Perez de la Vega et al. 1998). Avena atlantica Baum et Fedak, 1985, Canad. Jour. Bot., 63: 1057–1060; Ladiz., 1989, Rep. Work. Gr. Avena,: 19–32; Rodionova et al. 1994, Cult. Fl.,: 117–120. Annual. Juvenile growth prostrate. Flowering stems geniculate, about 95 cm high. Panicle equilateral. Spikelets awned small and containing 2–3 florets. Glumes nearly unequal with 9–10 veins. Lemma tips biaristulate. Only the lower floret disarticulates at maturity. Awn inserted at lower 1/3 of the lemma. Callus round-elliptical. A. atlantica is a Moroccan endemic. Its population grows on the Atlantic and Mediterranean coasts. The species climbs up the northwestern slopes of the Atlas Mountains up to 1,000 m. The most favored by the species are very dry red-brown sandy and stony soils in the foothills (Baum and Fedak 1985a; Leggett et al. 1992). Tetraploid Species Avena barbata Pott ex Link autopsia spec. orig., 1796, Herb. Acad. Sc. Petrop.; idem in Link in Schrader, 1799, Jour. Bot., 2: 315; Ledeb., 1853, Fl. Ross., 4: 412; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 112; Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6: 40, 45, excl. var. caspica et var. longiglumis Hausskn.; Roshevitz 1934, Fl. USSR, II: 262; Mordvinkina 1936, Cult. Fl. USSR,: 422; Mansfeld., 1959, Kulturpflanze Beih., 2: 479; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 242; Rodionova et al. 1994, Cult. Fl.,: 91–97; Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. hirsuta Moench, 1802, Meth. Suppl.: 64; Roth, 1806, Catal. Bot., 3: 19; Marschall et Bieberstein, 1819, Fl. Taur.-cauc. suppl. III: 82; Baum 1974, Canad. Jour. Bot., 52: 2243. – A. hispida Hort. ex Steud., 1840, Nomencl. Bot., 2, 1: 172. – A. japonica Steud., 1855, Syn. Pl. gram.,: 231. – A. strigosa subsp. barbata (Pott) Thell., 1911, Veirt. 3 Avena Natur. Ges., LVI: 330; idem. 1928, Rec. trav. bot. neer., XXVa: 434, excl. var. solida Hausskn.; Malz., 1930, Ovs. & Ov.; 268. – A. lusitanica Tab. Mor., 1939, Bot. Soc. Brot., ser. 2, 13: 624; Baum 1977, Monogr. Gen. Avena: 129. – A. matritensis Baum 1977, Monogr. Gen. Avena: 129. – A. barbata subsp. castellana Romer. Zarc., 1990, Lagascl., 16: 252. Annual. Juvenile growth prostrate to erect. Flowering stems erect, 65–210 cm high. Panicle equilateral. Spikelets awned medium sized and containing 2–4 florets. Glumes nearly unequal with 9–10 veins. Lemma tips biaristulate. All florets disarticulate at maturity. Awn inserted at 1/2 of the lemma. Callus round. A. barbata with the highest degree of genetic polymorphism is observed throughout the Mediterranean region and along the European Atlantic coast. In the East, it is spread through Asia Minor up to the Himalayas and also occurs on the Ethiopian Plateau at altitudes around 2,200–2,800 m. It grows on limy soils, on hilly terrain with loess-like soils, in depressions with alluvial deposits on red sandy, volcanic, and heavy basalt soils, which form on metamorphic rocks. It is also spread in Brazil, Japan, and Australia as an adventive species (Malzev 1930; Roshevitz 1934, 1937; Vavilov and Bukinich 1959; Ladizinsky 1971c, 1975; Baum et al. 1972a; Kliphuis and Wieffering 1972; Whalley and Burfitt 1972; Loon van 1974; Dillenburg 1984; ; Romero Zarco 1990; Sheidai et al. 2002; Loskutov 2007). Avena vaviloviana (Malz.) Mordv., 1936, Cult. fl. USSR,: 422; Mansfeld., 1959, Kulturpflanze Beih., 2: 479; Baum 1974, Canad. Jour. Bot., 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 90–91. – A. strigosa subsp. vaviloviana Malz., 1930, Ovs. & Ov., 278. – A. barbata subsp. vaviloviana (Malz.) Nevski 1934, Work Asie. univ., ser. 8в, 17: 4; Ladiz. et Zohary, 1971, Euphyt.,: 385–387. Annual. Juvenile growth prostrate to erect. Flowering stems erect, 80–110 cm high. Panicle unilateral. Spikelets awned medium sized, and containing 2–3 florets. Glumes equal, longer than florets, 20–25 mm long with 8 veins. Lemma tips biaristulate 1 mm long with 2 denticula. All florets disarticulate at maturity. Awn inserted at 1/2 of the lemma. Callus short, oval, about 3–5 mm long. A. vaviloviana is an endemic species in Ethiopia, Eritrea, and Yemen. In these countries, it occurs everywhere and is very common on the Ethiopian Plateau at altitudes between 2,200 and 2,800 m, mostly on cultivated fertile lands (Mordvinkina 1936; Vavilov 1965b; Ladizinsky 1975). Avena agadiriana Baum et Fedak, 1985, Canad. Jour. Bot., 63: 1379–1385; Ladiz., 1989, Rep. Work. Gr. Avena,: 19–32; Rodionova et al. 1994, Cult. Fl.,: 120. Annual. Juvenile growth prostrate. Flowering stems geniculate, about 60 cm high. Panicle unilateral. Spikelets small, and containing 2 florets. Glumes nearly unequal, 15–18 mm long with 8 veins. Lemma tips bidentate. Only the lower floret disarticulates at maturity. Awn inserted at lower 1/3 of the lemma. Callus rounded-elliptical. A. agadiriana is a Moroccan endemic species. A number of its populations have been collected from the Atlantic and Mediterranean coasts. The species prefers red-brown sandy and stony soils (Baum and Fedak 1985b; Leggett et al. 1992). Avena magna Murphy et Terrell, 1968, Science, 159: 103; Ladiz. et Zohary, 1971, Euphyt.,: 385–387; Baum 1974, Canad. Jour. Bot., 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 98–100. – A. moroccana Gdgr., 1908, Bull. Soc. Bot. France, 55: 658; Baum 1977, Monogr. Gen. Avena: 129. Annual. Juvenile growth prostrate. Flowering stems geniculate, 65–100 cm high. Panicle unilateral. Spikelets large and containing 3–4 florets. Glumes wide, long, membranous, nearly unequal with 8–10 veins. Lemma tips bidentate. Only the lower floret disarticulates at maturity. Awn inserted at 1/2 of the highly pubescent lemma. Callus strongly pubescent, rounded. A. magna (syn. A. moroccana Gdgr.), an endemic species, have been collected on the Moroccan coast and in the mountains within the altitudinal range from 500 up to 1,000–1,300 m. Wherever it occurs, this species grows on fertile, loose, reddish-brown alluvial loamy soils (Rajhathy et al. 1966; Leggett et al. 1992). Avena murphyi Ladizinsky, 1971, Israel Jour. Bot., 20: 24–27; Baum 1974, Canad. Jour. Bot., 52: 2243; Rodionova et al. 1994, Cult. Fl.,: 97–98; Romero Zarco 1996, Lagascal., 18, 2: 171–198. Annual. Juvenile prostrate. Flowering stems geniculate, 70–80 cm high. Panicle equilateral. Spikelets large and containing 2–6 florets. Glumes equal with 8 veins. Lemmas wide, equal, mostly glabrous. Lemma tips bidentate. Only the lower floret disarticulates at I.G. Loskutov and H.W. Rines AU1 maturity. Awn inserted at lower 1/4 of the pubescent lemma. Callus oval. A. murphyi originates from limited natural areas in southern Spain and northern Morocco, where it grows in a typically Mediterranean climate on thick alluvial soils (Ladizinsky 1971a; Leggett et al. 1992; Perez de la Vega et al. 1998). Avena insularis Ladizinsky 1998, Gen. Res. Crop Evol., 45: 263–269; Hanelt, 2001, Mansf. Encycl. Agr. Hort. Crops, 5: 2507. Annual. Juvenile growth prostrate. Flowering stems geniculate, about 60 cm high. Panicle unilateral. Spikelets V-shaped, large, and containing 3–5 florets. Glumes long, equal, with 9–10 veins. Lemmas medium sized, strongly pubescent. Lemma tips bisubulate or shortly biaristate. Only the lower floret disarticulates at maturity. Awn inserted at lower 1/3 to 1/2 of the pubescent lemma. Callus elliptical. A. insularis has been found in Southern Sicily and then in Tunisia at altitudes from 50 to 150 m on alluvial clay soils with sand-clay and conglomeratestony subsoils varying in color from whitish to gray, black, brown, or red, with a pH of 7.8, with rainfall around 400 mm. Later on, the populations of this species were collected on the same type of soil in Tunisia (Ladizinsky 1998, Ladizinsky and Jellen 2003). Avena macrostachya Balansa et Durieu, 1854, Bull. Soc. Bot. France 1: 318; Baum 1974, Canad. Jour. Bot, 52: 2243; Ladiz., 1989, Rep. Work. Gr. Avena,: 19–32. – Helictotrichon macrostachyum Holub 1958, Pflanzentaxonom,: 101–133. Perennial, outcrossing autotetraploid plant. Juvenile growth semi-prostrate. Flowering stems erect, about 100 cm high. Panicle equilateral. Floret anthers large, yellow, with anthocyan. Spikelets small with the awns, and containing 6–8 florets. Glumes short, very unequal, lower glume one-half of upper one with 7 veins. Lemmas medium long, slightly pubescent. Lemma tips bisubulate. Awns inserted in lower 1/3 of the lemma. All florets disarticulate at maturity. Callus linear-elongated. A. macrostachya is a narrow endemic species found at the very edge of snows (1,500 m) in the mountainous regions of Djurdjura and Aures (the Atlas Mountains) in Northeastern Algeria. It grows predominantly on limy soils (Baum 1977; Baum and Rajhathy 1976; Baum et al. 1975; Guarino et al. 1991). Hexaploid Species Avena sterilis L., 1762, Sp. Pl., ed. 2:118; Ledeb., 1853, Fl. Ross., 4:412 incl. A. fatua b-trichophylla (C. Koch.) Griseb.; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 109, excl. A. sterilis var. minor; Grillet et Magne, 1875, Fl. Franc. Ed. 3:532, excl. subsp. ludoviciana Durieu et Magne, subsp. barbata Gillet et Magne; Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6:38, 44, excl. A. sterilis f. abbreviata Hausskn.; Thell., 1911, Veirt. Natur. Ges., LVI: 312–319, excl. A. sterilis subsp. ludoviciana (Durieu) Gillet et Magne; idem, 1928, Rec. trav. bot. neerlan., 25a: 429–433; Malz., 1930, Ovs. & Ov.: 359, quoad subsp. macrocarpa (Monch) Brig.; Roshevitz 1934, Fl. USSR, II: 269; Mordvinkina 1936, Cult. Fl. USSR,: 417; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 238, excl. subsp. ludoviciana (Durieu) Gillet et Magne; Rodionova et al. 1994, Cult. Fl.,: 86–90; Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. macrocarpa Moench, 1794, Meth. Pl.: 196. – A. atherantha Presl, 1820, Cyper. Gram. Sicul.,: 30; Baum 1977, Monogr. Gen. Avena: 129. – A. maxima Presl., 1826, Fi. Sic.,: 44; Baum 1974, Canad. Jour. Bot., 52: 2243. – A. sterilis subsp. macrocarpa Briq., 1910, Prodr. fl. Cors., 1: 105; Thell., 1911, Veirt. Natur. Ges., LVI: 312–319. – A. sativa subsp. sterilis (L.) Ladiz. et Zohary, 1971, Euphyt., 20: 385–387. Annual. Juvenile growth erect to prostrate. Flowering stems erect, 30–145 cm high. Panicle equilateral. Spikelets V-shaped, large, and containing 3–5 florets. Glumes large equal. Lemma tips bidentate. Only the lower floret disarticulates at maturity. Awn inserted at lower 1/2 of the slightly moderate pubescent lemma. Callus rounded. A. sterilis is widely spread throughout the Mediterranean, from the Atlantic Ocean to the Himalayas, namely in Spain, Portugal, Italy, Switzerland, southern France, northern Iran, Turkey, Ukraine, Transcaucasia, in all countries of northern Africa, and in Ethiopia. The highest degree of genetic polymorphism may be observed in the areas with rainfall from 50 to 800 mm, on almost all types of sandy and clay soils, on basalt rocks, and at altitudes above 600–700 m. Numerous form of A. sterilis can be found at present in Japan and South Korea (Roshevitz 1934; Holden 1966; Ladizinsky 1975; Yamaguchi 1976; Garcia-Baudin et al. 1978, 1981; Schuler 1978; Maillet 1980; Brezhnev and Korovina 1981; Costa 3 Avena AU2 1988; Romero Zarco 1994; Kanan and Jaradat 1996; Loskutov 2007). Avena ludoviciana Durieu, 1855, Act. Soc. Linn. Bordeaux, 20: 41; Roshevitz 1934, Fl. USSR, II: 269; Mordvinkina 1936, Cult. Fl. USSR,: 418; Rodionova et al. 1994, Cult. Fl.,: 78–82. – A. persica Steud., 1855, Syn. plan. gram., I: 230. – A. sterilis var. minor Coss. et Durieu, 1855, Expl. sc. Alger., 2: 109. – A. sterilis subsp. ludoviciana (Durieu) Gillet et Magne, 1875, Fl. Fr., Ed. 3: 532; Thell., 1911, Veirt. Natur. Ges., LVI: 313; Malz., 1930, Ovs. & Ov., 363; Tzvelev, 1976, Poaceae USSR,: 239; Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. sterilis f. abbreviata Hausskn., 1894, Mitteil. Thur. Bot. Ver., 6: 39, 44. – A. trichophylla C. Koch 1848, Linnaea, XXI: 393; Roshevitz 1934, Fl. USSR, II: 269; Baum 1974, Canad. Jour. Bot., 52: 2243. – A. sterilis subsp. trichophylla (C. Koch) Malz., 1930, Ovs. & Ov.,: 363; Tzvelev, 1976, Poaceae USSR,: 238. Annual. Juvenile growth erect to prostrate. Flowering stems erect, 40–150 cm high. Panicle equilateral. Spikelets large and containing two or rarely 3 florets. Glumes equal, 25–30 mm long. Lemma tips bidentate. Only the lower floret disarticulates at maturity. Awn inserted at lower 1/3 of the pubescent lemma. Callus rounded. A. ludoviciana is found throughout Europe, in eastern Mediterranean, Ukraine, southern Russia, Azerbaijan, Central Asia, Iran, Asia Minor, southwestern Asia, Afghanistan, as well as along the entire coast of northern Africa and Mediterranean Sea. It grows on almost all types of sandy and clay soils and demonstrates wide genetic diversity. The species has been brought over to northern and southern Australia and to New Zealand (Roshevitz 1934; Romero Zarco 1994, 1951; Vavilov and Bukinich 1959; Holden 1969; Guillemenet 1971; Kropac and Lhotska 1971; Whalley and Burfitt 1972; Garcia-Baudin et al. 1978; Schuler 1978; Costa 1988; Loskutov 2007). Avena fatua L. 1753, Sp. Pl.,: 80; idem, 1762, Ed. 2: 113; Lebed., 1853, Fl. Ross., 4: 412, excl. A. fatua., b-trichophylla (C. Koch) Griseb. et syn. A. byzantina C. Koch; Coss. et Durieu, 1855, Expl. sc. Alger., 2: 109; Hausskn., 1885, Mitt. geogr. Ges., 3: 237–239; idem, 1894, Mitteil. Thur. Bot. Ver., 6: 37, 45, exl. subsp. sativa Hausskn.; Thell., 1911, Veirt. Natur. Ges., LVI: 319; Malz., 1930, Ovs. & Ov.,: 287; Roshevitz 1934, Fl. USSR, II: 267; Mordvinkina 1936, Cult. Fl. USSR,: 402–403; Baum 1974, Canad. Jour. Bot., 52: 2243; Tzvelev, 1976, Poaceae USSR,: 239; Rodionova et al. 1994, Cult. Fl.,: 72–78; Romero Zarco 1996, Lagascal., 18, 2: 171–198. – A. hybrida Peterm., 1841, Fl. Bienitz: 13; Koch, 1844, Syn. Fl. Germ. Helv. Ed. 2.II: 917; Steudel, 1855, Syn. Pl. gram.: 230; Baum 1977, Monogr. Gen. Avena: 129. – A. sativa subsp. fatua (L.) Thell., 1911, Veirt. Natur. Ges., LVI: 319; Ladiz. et Zohary, 1971, Euphyt.,: 385–387. – A. septentrionalis (Malz.) Roshevitz, 1934, Fl. USSR, II: 265; Baum 1974, Canad. Jour. Bot., 52: 2243. – A. meridionalis (Malz) Roshevitz, 1934, Fl. USSR, II: 266. – A. cultiformis (Malz.) Roshevitz, 1934, Fl. USSR, II: 268. Annual. Juvenile growth erect to prostrate. Flowering stems erect, 40–150 cm high. Panicle equilateral. Spikelets large and containing 2–3 florets. Glumes equal, 20–25 mm long. Lemma can be hairy or glabrous. Lemma tips bidentate. All florets disarticulate at maturity. Awn inserted at 1/2 of the lemma. Callus rounded. A. fatua grows on different soils under different climatic conditions ranging from the Tropics right up to the Polar Circle; it climbs high into the mountains up to the upper limit of crop cultivation (till 3,000 m) and demonstrates the highest degree of genetic polymorphism. Wild oat has penetrated almost all agricultural areas around the globe – from the Atlantic Ocean across Eurasia into Mongolia, Japan, and South Korea; spread throughout southern and northern Africa and got into North and South Americas, Australia, and New Zealand (Malzev 1930; Roshevitz 1934, 1937; Vavilov and Bukinich 1959; Guillemenet 1971; Baum et al. 1972a; Kuhn 1972; Whalley and Burfitt 1972; Nilsson et al. 1973; Yamaguchi 1976; Rines et al. 1980; Costa 1988). Avena occidentalis Durieu, 1865, Jard. Pl. Bordeaux, 2: 24; Hubbard, 1937, Fl. Trop. Afr., 10: 122; Baum 1971, Canad. Jour. Bot., 49: 1055–1057; Rodionova et al. 1994, Cult. Fl.: 82. Annual. Juvenile growth semi-erect to prostrate. Flowering stems geniculate, 45–100 cm high. Panicle equilateral. Spikelets large and containing 3–4 florets. Glumes equal, 16–20 mm long. Lemma can be hairy or glabrous. Lemma tips bisubulate or shortly biaristate. All florets disarticulate at maturity. Awn inserted at 1/2 of the lemma. Callus rounded. A. occidentalis occurs mostly on the Canary Islands (Spain), but according to Baum (1977) can be also found on the continent in Portugal, Egypt, I.G. Loskutov and H.W. Rines Ethiopia, as well as on the Azores and on Madeira Island, though initially it had been described in course of processing herbarium material from Algeria. The species tends to grow on alluvial soils in valleys and on stony slopes (Durieu de Maisonneuve 1845; Baum 1971). Therefore, wild Avena species occupy vast areas in the basins of the Mediterranean, Black, and Caspian seas and demonstrate a wide range of genetic diversity and good adaptation to different ecogeographical and soil conditions of the regions. A detailed morphological description and study of features of this or that oat species helps to define precisely its systematic position within a complicated system of the entire genus showing different ploidy levels and the huge morphological diversity determined by the vast natural habitat occupied by wild, weedy, and cultivated species. 3.1.1.3 Karyotype and Cytology of Avena Species Quite often, karyological analyses of cultivated plants and their wild relatives confirm their taxonomic status at the interspecific levels, thus making genomic characterization of the material in question possible. Karyological and cytological studies of Avena L. species have a long history (Avdulov 1931; Huskins 1927; Nikolaeva 1922; Rajhathy and Thomas 1974) (Table 3.2). Diploid Species with C Genomes The widest karyotype diversity is found within diploid oat species. All of them split into three groups: those containing predominantly subterminal Table 3.2 The karyotype structure of Avena species Species Genome Type of chromosomesa SMt2 STt2 SMt1 A. bruhnsiana Cv – – 1 A. ventricosa Cv – – 1 A. clauda Cp 1 – 1 A. pilosa Cp 1 – 1 A. prostrata Ap 1 – 1 A. damascena Ad 1 – 1 A. longiglumis Al 1 – 1 A. canariensis Ac 1 – 1 A. strigosa As 1 – 1 A. hirtula As 1 – 1 A. wiestii As 1 – 1 A. atlantica As 1 – 1 A. barbata AB 1 – 1 A. vaviloviana AB 1 – 1 A. abyssinica AB 1 – 1 A. agadiriana AB? – – 2 A. magna AC 1 1 1 A. murphyi AC 1 – 1 A. insularis AC? 1 – 1 A. macrostachya CC? – 2 – A. fatua ACD 1 – 2 A. sativa ACD 1 – 2 A. byzantina ACD 1 – 2 A. sterilis ACD 1 – 2 A. ludoviciana ACD 1 – 2 A. occidentalis ACD 1 – 2 Reference M – – – – 3 4 4 4 2 2 2 2 4 4 4 2 4 4 4 10 4 4 4 4 4 4 SM 1 – – – 1 1 1 1 2 2 2 2 6 6 6 7 2 6 7 – 7 7 7 7 7 7 ST 5 6 5 5 1 – – – 1 1 1 1 2 2 2 3 5 2 1 2 7 7 7 7 7 7 Emme (1932) Rajhathy (1961) Nikolaeva (1922) Nikolaeva (1922) Ladizinsky (1971b) Rajhathy and Baum (1972) Malzev (1930) Baum et al. (1973) Kihara (1919) Huskins (1926) Huskins (1926) Baum and Fedak (1985a) Kihara (1919) Emme (1932) Aase and Powers (1926) Baum and Fedak (1985b) Murphy et al. (1968) Ladizinsky (1971a) Ladizinsky (1998) Baum and Rajhathy (1976) Kihara (1919) Kihara (1919) Kihara (1919) Kihara (1919) Huskins (1926) Baum (1971) M median chromosomes; SM submedian, ST subterminal, SMt1, SMt2, STt2 satellite chromosomes with different type of satellites (t1 large satellite, t2 small satellite) a 3 Avena chromosomes (A. ventricosa, A. bruhnsiana, A. clauda, and A. pilosa), the species with one pair of such chromosomes (A. prostrata, A. wiestii, A. hirtula, A. atlantica, and A. strigosa), and those with only median and submedian chromosomes (A. damascena, A. longiglumis, and A. canariensis). A. ventricosa and A. bruhnsiana have been determined as diploid species with the somatic chromosome number equal to 14 (Emme 1932). Numerous studies have shown that A. ventricosa has the Av type of nuclear genome being similar in some features with A. pilosa (Rajhathy 1961, 1963). Later on, modification of the A. ventricosa genome relative to the clauda– pilosa complex has been confirmed (Thomas 1970) and underlined by assigning the Cv symbol to the A. ventricosa genome (Rajhathy 1966, 1971b). A study of an A. bruhnsiana population from the VIR collection revealed that all forms of this species collected in Azerbaijan possess five subterminal chromosome pairs (Loskutov 2007) as has been observed in an earlier investigation (Rajhathy 1971b). On the basis of similarity of submedian chromosomes, the species A. ventricosa and A. bruhnsiana have been identified as the very primitive ones in the Avena section (Rajhathy and Thomas 1974). A study of another pair of closely related diploid species, A. clauda and A. pilosa, has found them to have similar karyotypes (Nikolaeva 1922; Emme 1932). An analysis of karyotypes of the species has shown that the presence of two pairs of satellite chromosomes and five of medium subterminal chromosome pairs in the karyotype may be regarded as their main character. On the basis of karyological analysis, the genome formula of A. pilosa and A. clauda was changed from previously suggested Ap (Rajhathy 1966) to Cp and the species were defined as primitive ones in the Avena section (Rajhathy and Thomas 1974). The differences between these genomes confirm the rule deduced for the diploid species karyotypes (Thomas 1992), the essence of which is that the differences in the morphology of chromosomes in diploids are mainly in the position of the centromere and secondary constrictions. At the same time, all the abovementioned species with the asymmetric karyotype are not primitive in the true sense of the word; they are only archaic, i.e., undergoing evolution at a slower bradytelic type (Stebbins 1971). The diploid Cp and Cv genome species were studied using C-banding and fluorescence in situ hybridization (FISH). Species with the C genome differed considerably from the species of the A genome group in the karyotype structure, heterochromatin type and distribution, and position of 5S and 45S rDNA loci. These facts confirmed that the C genome had diverged from the ancestral genome before the radiation of the various A genome group. Presumably, further evolution of the A- and C-genome species occurred separately (Shelukhina et al. 2008b). Diploid Species with A Genomes The number of chromosomes in somatic cells of A. longiglumis is 14 (Malzev 1930) that was later confirmed by other researchers (Holden 1966). A study of different populations of this species revealed that the early flowering short-stem forms had two pairs of satellites, while the late flowering tall forms had just one pair (Morikawa 1992). Some researchers believe the genome of this species to be similar to that of A. strigosa (Steer et al. 1970), while others think it is different (Griffiths et al. 1959). The genome had been designated as Al (Rajhathy and Morrison 1959), and later, the difference of the genome of this species from other variants of A genome has been confirmed by a variety of other methods (Rajhathy 1961; Thomas and Jones 1965; Murray et al. 1970). Chromosome number and karyotype structure were determined for A. prostrata (Ladizinsky 1971b), and its genome was designated as Ap (Rajhathy and Baum 1972). The number of chromosomes of A. damascena is 14 (Rajhathy and Baum 1972). Its karyotype (designated as Ad) resembles that of A. longiglumis very much with the only difference in the ratio (1:1) between the large satellite and the chromosome arm to which it is attached (Rajhathy and Thomas 1974). On the other hand, later evidence indicated that this species occupied a unique position in the A-genome diploid species based on the pattern of in situ hybridization with rDNA probes (Shelukhina 2008). A. canariensis was shown to be a diploid species (Baum et al. 1973). The karyotype of this species (Ac) is similar to the Al (A. longiglumis) and Ad (A. damascena) karyotypes with the only difference being one satellite slightly larger. This species was supposed to be the A genome donor for hexaploid oats (Baum et al. AU3 I.G. Loskutov and H.W. Rines 1973) and for the AC-genome tetraploid species (Leggett 1980). Different populations of this species had different numbers of satellited chromosomes. The early flowering population from Lanzarote Island (Spain) was found to have just one chromosome pair with a satellite, while the late flowering populations had two pairs of SAT chromosomes (Morikawa and Leggett 1990). The diploid oat species containing the Al and Ac genomes were studied by C-banding and in situ hybridization. Their karyotypes displayed similar C-banding patterns but differed in size and morphology of several chromosomes, presumably because of structural rearrangements that occurred during the divergence of A genomes from a common progenitor. A considerable similarity of A. canariensis and A. longiglumis to Avena diploid species carrying the As genome variant was demonstrated (Shelukhina et al. 2008a). The chromosomes number of cultivated A. strigosa is 2n ¼ 14 (Kihara 1919). The karyotype of this species was characteristic of the whole diploid sandy oats group that included A. hirtula and A. wiestii with the As genome (Huskins 1926; Emme 1932; Shepeleva 1939; Rajhathy 1961), though initially the former species had been grouped with the tetraploids (Huskins 1926, 1927). A study of the A. wiestii karyotype and its comparison with the A genome of hexaploid species had initially confirmed their similarity (Holden 1966; Thomas and Thomas 1970), and its partial structural modification has been proved by a number of authors (Sadanaga et al. 1968). A cytogenetic investigation of the As-genome species has displayed significant closeness of A. strigosa and A. weistii and a somewhat isolated position of A. hirtula in this group. The results of this investigation contradict the findings of other authors that the rearrangement of chromosome 7 is species-specific to A. strigosa because all three studied species (as well as A. hispanica) are similar morphologically as well as in terms of the chromosome C-banding pattern (Badaeva et al. 2005). Later-discovered species A. atlantica, with the number of chromosomes in somatic cells 2n ¼ 14, had a similar karyotype as the As genome (Baum and Fedak 1985a), though its plants differed very much morphologically from other species in this group. A. strigosa-specific carried a chromosomal translocation relative to the diploid species A. atlantica and A. hirtula (Loarce et al. 2002). Tetraploid Species with CC Genomes A. macrostachya, the most primitive perennial outcrossing species, has been identified as an autotetraploid (2n ¼ 28). It has a symmetrical karyotype mainly with median chromosomes, which differ little in size and represent a gradually decreasing series in terms of length. The presence of a large number of chromosomes, which are similar in terms of size and structure, favor its autotetraploid nature. Cytologically, the nature of this species has been confirmed by behavior of chromosomes in meiosis. On the average, 56.6% of chromosomes formed quadrivalents, which is characteristic of the majority of autotetraploids in the Poaceae family (Baum and Rajhathy 1976). A symmetrical karyotype is not characteristic of the C-genome diploid species (Pohler and Hoppe 1991), but at the same time, this character brings A. macrostachya closer to the A-genome oat species (Loskutov 2001b). The presence of large C-heterochromatic blocks in the chromosomes’ pericentromeric regions indicates similarity between this and the C-genome species and it is supposed that this species can have the hitherto undescribed CmCm genome (Rodionov et al. 2005). At the same time, the karyotype symmetry suggests its primitive nature, being confirmed by outcrossing, perennial type of development, and a complex of morphological and cytological characteristics. According to Levitsky’s (1976) results in 1931 obtained and those of Stebbins (1971) perfectly symmetrical karyotype is an indicative of species primitiveness. Tetraploid Species with AB Genomes Morphologically, karyotypes of tetraploid species are subdivided into two groups that have two distinctively different genomes. In the first place, the studies of tetraploid species refer to the chromosome number analysis in the wild species A. barbata (Kihara 1919; Emme 1932; Shepeleva 1939). Morphologically, chromosomes of the tetraploid species differ somewhat from those of the diploid species belonging to the strigosa group, and the AsAb formula has been used to designate their karyotype (Holden 1966). On the other hand, the genome of this group of species has been designated as AB (Ladizinsky 1973b) as it was AU4 AU5 3 Avena determined earlier that the A genome of the tetraploid species was similar to the As genome of the diploid ones (Ladizinsky and Zohary 1968). A similarity of the main karyotypic features with other tetraploid species with AB-genomes has been confirmed by many researchers (Rajhathy and Morrison 1959; Thomas and Thomas 1970). This group includes two Ethiopian endemics: A. vaviloviana, a wild species (Emme 1932), and cultivated A. abyssinica (Aase and Powers 1926; Emme 1932). All these species have one and the same karyotype and AB genome composition. The recently discovered species A. agadiriana has been classified as tetraploid (Baum and Fedak 1985b). Its karyotype does not resemble those of any other tetraploids (Baum and Fedak 1985b), still its genome is presumed to be AB (Leggett 1988), though this species has an absolutely different morphological structure of lodicules and of the lemma tip. A study of different populations of this species has shown the early flowering forms to have three pairs of satellited chromosomes, while the late flowering ones had only two (Morikawa 1991, 1992). The tetraploids A. abyssinica, A. vaviloviana, A. barbata, and A. agadiriana have been studied using C-banding and in situ hybridization, which confirmed affiliation of all the four species with the AB genome group and demonstrated significant isolation of A. agadiriana. A supposition has been made that A. abyssinica, A. vaviloviana, and A. barbata had originated from a common tetraploid progenitor: however, the species diverged due to structural chromosome rearrangements and changes in the polymorphism system. Phylogenetic closeness has been demonstrated of the A and B genomes of these species to the A-genome diploids. The most probable progenitor of the A genome for A. abyssinica, A. vaviloviana, and A. barbata is an As-genome species. The second diploid progenitor of these three species has not been identified, but most likely, it does not belong to the Asgenome group. Diploid progenitors of A. agadiriana also have not been established; however, it is supposed that A. damascenа could be one of them (Shelukhina et al. 2009). FISH and Southern hybridization were used to investigate the chromosomal distribution and genomic organization of tetraploids. The study indicates that the Ethiopian endemic species A. abyssinica and A. vaviloviana have diverged from A. barbata. Differences between A. barbata and A. vaviloviana genomes were also revealed by both FISH and Southern hybridization using pAs120a rDNA probes. Whereas two B-genome chromosome pairs were found to be involved in intergenomic translocations in A. vaviloviana, FISH detected no intergenomic rearrangements in A. barbata (Irigoyen et al. 2001). Tetraploid Species with AC Genomes A. magna (Murphy et al. 1968) and A. murphyi (Ladizinsky 1971a, d) represent the second group of tetraploid species. It has been established that the karyotype of A. magna differs from those of other tetraploid species and does not contain the B genome (Murphy et al. 1968). Later, this genome was designated as AC instead of the previously determined AD genome (Murray et al. 1970). A cytogenetic analysis of A. magna and A. barbata hybrids has found these species to have little relation to each other (Thomas 1988). Further study showed that the karyotype of A. murphyi has a somewhat different structure (Rajhathy and Thomas 1974), though this species also have the AC genome (Rajhathy and Thomas 1974). Another tetraploid species, A. insularis, is morphologically very similar to the above-mentioned group. The species was not found to contain the A genome (Ladizinsky 1999): presumably, this species contains either AC or CD genome. Crosses between A. insularis populations collected on Sicily and in Tunisia gave partially sterile hybrids, confirming their genetic remoteness (Ladizinsky and Jellen 2003). Evaluation of A. insularis C-banding karyotype showed that the Sicilian wild tetraploid is a close relative of A. magna and A. murphyi and is more plausible than either of these two species as the immediate tetraploid progenitor of A. sterilis and the other hexaploid oats (Jellen and Ladizinsky 2000). A comparative cytogenetic investigation of three tetraploid species A. magna, A. murphyi, and A. insularis has shown these species to be similar in terms of C-banding patterns of a number of chromosomes. According to the data obtained, A. insularis is phylogenetically closer to A. magna, while A. murphyi is somewhat isolated from two other species. It may be supposed that all of the three studied species have a common tetraploid progenitor and their divergence is associated with different species-specific chromosome rearrangements. Apparently, the evolution of I.G. Loskutov and H.W. Rines A. murphyi proceeded independently from other species (Shelukhina et al. 2007). Hexaploid Species Hexaploid species have similar karyotypes and in general have the same genome composition. Investigations of these species started by determining chromosome numbers for A. fatua, A. sterilis (Kihara 1919; Emme 1932), and A. ludoviciana (Huskins 1926). Eighteen chromosome pairs of hexaploid A. sativa and A. fatua were morphologically similar, while three pairs showed very different morphology (Shepeleva 1939). Later on, it was determined that such karyotype structure is typical for hexaploids. A. fatua, A. sterilis, A. byzantina, and A. sativa have been found to possess the same ACD genome composition (Rajhathy and Morrison 1959; Rajhathy 1966). Initially, the genome was designated as ABC (Nishiyama 1929), but then, the genome formula was changed to ACD (Rajhathy and Morrison 1959; Rajhathy 1963). It has been later supposed that A genome was the Ac genome of the diploid A. canariensis (Thomas and Leggett 1974), while the Cv genome of the diploid A. bruhnsiana was the source of the C genome (Rajhathy 1966). However, similarity of the As genome to the A genome of hexaploid species has not been confirmed (Ladizinsky 1969). A cytogenetic study of populations of wild Mediterranean species concluded that A. pilosa (Cp) and the A. strigosa (As) group are the basic variants of the C and A genomes, respectively, while other species (A. ventricosa (Cv) and A. longiglumis (Al)) have structurally altered derivative karyotypes (Rajhathy 1963). On the contrary, a study of the AB genome of the tetraploid A. barbata did not identify it as a progenitor of the hexaploid species (Thomas et al. 1975). Thus, the modern karyological and cytological investigations make it possible to identify chromosomes in a karyotype and thus provide the possibility of making a judgment about intraspecific and genomic differences at the chromosomal level. Therefore, the karyotypic peculiarities characterizing individual species facilitate a better understanding of the position of each species in the system of genus Avena and help to elucidate taxonomic problems. 3.1.1.4 Agricultural Status of Wild Oat Species Some Avena species are truly wild and grow in natural habitats on different types of soils, and some of them are weeds. They comprise noxious weeds in agricultural fields such as A. fatua and A. sterilis, including the well-known A. ludoviciana and A. barbata, and truly wild plants as native components of their local flora as A. clauda, A. pilosa, A, ventricosa, A. prostrate, A. damascena, A. hirtula, A. wiestii, A. canariensis, A. atlantica, A. murphyi, A. agadiriana, A. insularis, etc. (see Sect. 3.1.1.2). All oat species prefer in general a temperate hot, semi-arid and dry climate; in the east, they prefer temperate semi-arid or temperate arid climate and do not grow in hot and dry climates. For diploid and tetraploid species, a combination of favorable climate types in the African continent occurs in some regions of Morocco, Algeria, and coastal regions of Tunisia in the north, and Ethiopia in the east. In the European continent, this combination is offered by the southern Europe, especially Spain, Mediterranean islands, as well as coastal and mountainous territories of the Black and Caspian sea basins. In the Asian continent, favorable climates may be found in Israel, Jordan, Syria, Turkey, Azerbaijan, northern parts of Iraq, Iran, and Afghanistan, and Central Asian states, and it is here that some of the diverse species of oat are found. Hexaploid species A. sterilis and A. ludoviciana grow in the same territories and occupy wider areas to the south and north of the natural habitat. A. fatua has a wider natural habitat, which encompasses all European countries up to the northern ones as well as territories of Russia, Mongolia, and China. This species has never occurred below the 25th parallel in the Asian continent. In the African continent, this species occupies the entire northern part and reaches as far as Ethiopia and northern Kenya in the east. A. barbata, A. ludoviciana, A. sterilis, and A. fatua occur as adventitious species in most regions of the American continent, on the southern tip of Africa, in New Zealand, and Australia (see Sect. 3.1.1.2). The the economic importance of the wild diploid species such as A. clauda and A. pilosa occurring in arid semi-deserts in the Caucasus and A. canariensis growing in the Canaries (Spain) is not great as they have limited value as forage for cattle (Grossheim 1967; Morikawa and Leggett 1990); however, the AU6 AU7 3 Avena nutritive value of another tetraploid species, A. barbata, is of special importance for breeding. The hybrids produced in Japan exceed standard cultivars by 15–40% in terms of total green mass yield. In the US, the latter species is regarded as a promising forage (Marshall and Jain 1968, 1970; Coffman et al. 1970). According to a number of explorers, the hexaploid species A. fatua and A. ludoviciana represent a fairly good pasture forage in the Caucasus and Southern Russia and are promising for green fodder crop breeding and use for fodder purposes (Roshevitz 1934; Grossheim 1967; Musaev et al. 1976). A thorough study of local populations of A. sterilis applying different methods was carried out in California with the aim of involving them in fodder crop breeding (Singh et al. 1973). In India, A. strigosa, A. magna, A. sterilis, and A. fatua are widely used for breeding fodder cultivars (Choube et al. 1985). Thus, on the one hand, wild oat species are noxious weeds of agricultural crops, while on the other, they can be used as natural forages for agricultural purposes. 3.2 Conservation Initiatives 3.2.1 Evaluation of Genetic Erosion at Space and Time Scale Population growth, urbanization, developmental pressures on the land resources, deforestation, changes in land use patterns, and natural disasters are contributing to abundant habitat fragmentation and destruction of the crops and their wild relatives. Social disruptions or wars also pose a constant threat of genetic wipeout of such promising diversity. Overexploitation and also the introduction of invasive alien species are the other factors contributing to the loss of genetic resources. More recently, global warming and a high degree of pollution have also been recognized as further causes for the loss of biodiversity (Hammer and Teklu 2008). Genetic diversity among domestic lines or cultivars is always more restricted than that of the parents or the general plant population(s) from which the cultivars originated. As improvements are made through further recombination and selection among progenies, genetic diversity narrows even more. When the oat crop was developed from the original wild species, early agriculturists selected successive individual plants over a long time on the basis of favorable appearance, seed or green forage production or both under cultivation, and personal preferences of those who harvested and saved seed for replanting. Each primitive cultivar had less genetic diversity than the source population or the species (Wesenberg et al. 1992). Loss of such diversity is critical because it could be a source of pest resistance or adaptive characters not recognized at the time. Loss of genetic diversity associated with oat domestication and other species, however, dwarfs the loss of genetic diversity that modern plant breeders have been responsible for in the process of cultivar development. Thus, a continuing effort is required to conserve most wild Avena populations, old landraces, and populations; otherwise they will be lost forever. Two types of genetic erosion can be distinguished in wild populations: the extinction of populations and the drastic change of genetic structure of populations. The first type means the total loss of genetic resources, which results from complete destruction of habitats, and all genotypes and/or alleles being lost, while the second one originates from isolated local populations due to the deterioration of habitats. In another case, there is significant risk of the ultimate loss of diversity because smaller populations are vulnerable to demographics and the decline in fitness associated with genetic drift and inbreeding. Genetic drift is the random change in allele frequency that occurs because gametes transmitted from one generation to the next carry only a sample of the alleles present in the parental generation (Hammer and Teklu 2008). The threatened wild oat species and those with a shrinking natural habitat include A. clauda, A. pilosa, A. ventricosa, A. bruhnsiana, A. damascena, A. prostrata, A. canariensis, A. atlantica, A. agadiriana, A. magna, A. murphyi, A. insularis, and A. occidentalis. All these species represent components of natural habitats in some countries on the Mediterranean coast of Africa, southern coast of Spain, Italy, Greece, and a part of Mediterranean and Atlantic islands. Most natural habitats are disjunctive due to the island location of habitats; therefore, the species are narrow endemic in the outlined area. At present, natural habitats of these species are shrinking because of the I.G. Loskutov and H.W. Rines anthropogenic pressure. Apparently, the abovementioned species once had wide natural habitats. For instance, Malzev (1930) noted in his work that in the early twentieth century, A. ventricosa used to be widely spread in Algeria and in Cyprus, while at present, the natural habitat of this species is very narrow, with single plants occurring in these regions. According to researchers who recently have been collecting A. bruhnsiana, in the Apsheron Peninsula (Azerbaijan), this species is disappearing at high rate, most likely because of activities of oil development and construction companies in this territory (Loskutov 2007). The endemic diploid species A. canariensis occurs only within a limited area of the Canaries (Spain); another tetraploid species (A. agadiriana), isolated from that diploid and resembling it morphologically, is distributed in a very narrow range near Agadir in Morocco. According to Spanish and Moroccan researchers, genetic diversity of the tetraploid species A. murphyi has sharply decreased in comparison with the results of previous collecting, and in some places, it could not be found at all (Perez de la Vega et al. 1998; Saidi and Ladizinsky 2005). The recently described new tetraploid species A. insularis, which has been discovered in both Italy (Sicily) and Tunisia, also has a very narrow natural habitat. Of special importance is the most primitive oat species – the perennial outcrossing tetraploid A. macrostahya. This narrow endemic species has been found at the very edge of snows (1,500 m) in the mountainous regions of Djurdjura and Aures (the Atlas Mountains) in northeastern Algeria only. Apparently, all the above-listed species are losing a part of their habitats, and some genotypes and/or alleles are being lost; other species may experience genetic erosion as a result of genetic drift and inbreeding caused by the shrinkage or split of natural habitats, or the decrease in plant number in a certain territory. The problem of genetic erosion through inappropriate maintenance of ex situ collections is widely recognized. Genetic erosion can occur at many stages in the preparation, subsampling, exchange, storage, and regeneration of seed samples (Sackville Hamilton and Chorlton 1997). These authors also highlighted loss of diversity through genetic shifts and convergent selection during regeneration as a potentially severe and often underacknowledged problem. However, the different institutes are suffering from financial problems, lack of staff, and shortage of farms. The threat of loss of genetic integrity from regeneration of wild oat species is very high. The reason is that practically all Avena species originate from the Mediterranean and adjacent regions, while the ex situ collections are maintained predominantly in countries that are quite distant from the regions of collection and natural habitats. As a result, regeneration of these species in the regions where the genebanks conserving these accessions are located may lead to genetic shifts and convergent selection during regeneration. Lengthening of regeneration backlogs due to inadequate funding, lack of technical staff, and its low proficiency causes partial loss of germination by seed material, which, in turn, leads to the loss of genetic integrity of the non-regenerated accessions. The long-term storage strongly reduces the metabolism and therefore highly limits viability and seed vigor. In this case, poor germination potential and vigor in the field also are indicators of genetic erosion. Another important problem complicating regeneration of accessions and experienced by genebanks around the world in their work with wild oat species is the absence of distinct descriptors based on clearly visible and easily distinguishable morphological characters, which could be used for the identification of botanical diversity using morphological characters of the plant in the field and morphological characters of the kernels in the laboratory. On the whole, these problems may lead to genetic erosion of individual accessions even if they are under careful conservation and safety-duplication. 3.2.2 Attempts of In Situ and Ex Situ Conservation The conservation of plant diversity is of critical importance because of the direct benefits to humanity that can arise from its exploitation in improved agricultural and horticultural crops, because of the potential for development of new medicinal and other products and because of the pivotal role played by plants in the functioning of all natural ecosystems (Hammer and Teklu 2008). In formulating strategies for the conservation of any crop, it is essential to know areas of distribution and identify regions where its collecting for conservation activities could usefully be initiated. This will 3 Avena be due to a combination of high levels of genetic diversity at the site(s), interest of the user community in the specific genetic diversity found at or believed to be found at the site, lack of previous conservation activities, and imminent threat of genetic erosion (Maxted et al. 1997). There are two primary complementary conservation strategies, ex situ and in situ, each of which includes a range of different techniques that can be implemented to achieve the aim of the strategy. The products of conservation activities are primarily conserved germplasm, live and dried plants, cultures, and conservation data. The conservation materials are either maintained in their original environment or deposited in a range of ex situ storage facilities. To ensure safety, conservation products should be maintained at more than one location (Hammer and Teklu 2008). The great genetic diversity to be found in the traditional agriculture stocks in the centers of genetic diversity, where the wild or weedy relatives of crop species can be found, were called gene centers or centers of origin according to Vavilov (1926) and centers of diversity according to Harlan (1975). As agriculture progressed with the beginning of scientific plant breeding, modern varieties were widely distributed replacing landraces from cultivation. This increased the need to formally store plants and seeds in ex situ collections. Landraces were then gathered together, which resulted in fairly large collections, above all in the US and in Russia. The great Russian biologist N. I. Vavilov accumulated rich collections of diversity in the Institute of Plant Industry (now VIR) by systematically collecting material (Loskutov 1999). Wild species are much more difficult to maintain and to regenerate than the cultivated forms. Their safeguard is a major concern in the oat community. As the convention of biological diversity (CBD) and the International Treaty (IT) reinforce the national sovereignty on biological diversity, centers of diversity will need primary consideration in developing a global conservation strategy, also with respect to complementary actions of ex situ and in situ conservation. Such a complementary approach will not only increase the security of the conserved material, but it will also allow evolutionary processes to continue, use the safest conservation strategies, and facilitate a closer link between the more scientific orientated and static ex situ approach with the much more practically orientated and dynamic in situ conservation. In addition, it is expected that this complementary approach will also result in an improvement of the quality of conservation and of the knowledge of the existence of genetic material as well as in more transparency. These factors increase the possibility to integrate the various conservation strategies and to make use of the material collaboration, also through exchange, independently from where the material is located (ECPGR 2008). Among the various ex situ conservation methods, seed storage is the most convenient for long-term conservation of plant genetic resources. Traditionally, many crops are conserved as seed in gene banks. This involves desiccation of seeds to low moisture contents and storage at low temperature. The ex situ conservation of large numbers of cultivated plants depends on the longevity of the seeds. Most species belong to the orthodox seed type with a logarithmical progression of shelf-life as humidity and storage temperature are reduced (Hammer and Teklu 2008). The recently established Global Crop Diversity Trust has begun contributing to the development of regional and global crop-specific strategies aimed at more effective arrangements for ex situ conservation (www.croptrust.org). The Global Strategy for the ex situ conservation for oats was discussed at the meeting of genebank curators and stakeholders of oat in St. Petersburg in 2007. Ex situ conservation of wild oat species has provided fairly good results. Some of these species, especially hexaploid ones, can retain their germinating ability for 10–15 years at room temperature. Under controlled conditions, at þ4 С, 10 С, or 18 С and standard humidity, seeds of these species keep viability well and therefore retain genetic integrity for a long period. Unfortunately, until now, no research has been undertaken by genebanks to elucidate the influence of duration of different types of ex situ storage facilities on the oat species genetic integrity. Judging from the data on genetic integrity of oat landraces conserved at VIR in ex situ storage facilities for the last 80 years, a positive conclusion about genetic stability of the studied material can be made (Zelenskaya et al. 2004). In situ conservation is defined as the conservation of ecosystems and natural habitats, and the maintenance and recovery of viable populations of species in their natural surroundings, and, in the case of I.G. Loskutov and H.W. Rines domesticated or cultivated species, in the surroundings where they have developed their distinctive properties. The first decision concerning the establishment of a nature reserve for the in situ conservation of cereal species in Ethiopia was taken at the First International Wheat Congress in Rome in April 1927 following the N.I. Vavilov’s report entitled “Les centres mondiaux des genes du ble,” in which he formulated preliminary results of his collecting mission to Ethiopia (Loskutov 1999). Over 50 years had passed before this method of genetic diversity preservation was adopted by the international community. In situ conservation activities should be carried out for saving wild oat species, some of which are quite rapidly disappearing from Earth. Unfortunately, according to the Spanish researchers, only vegetation of the Canaries can at present be regarded as relatively protected from destruction, thanks to the ban on human activities expansion in effect on the islands. Among the species growing there are A. canariensis and A. occidentalis. At present, an EU project for the in situ conservation of the species of special importance for cultivated oat breeding (A. magna, A. murphyi and A. insularis) is being developed for implementation in Morocco, Spain, Italy, and Tunisia. 3.2.3 Germplasm Banks: National and International About 220,000 oat accessions in ex situ collections have been estimated in the state of the world’s plant genetic resources report. Large collections are held by the USDA (20,000 accessions), the PGRC, Canada (30,000 accessions), and within the framework of the ECP/GR (34,146 accessions), namely by the Vavilov Institute of Plant Industry (VIR, Russia) (about 12,000 accessions), which has a collection of about 10,000 accessions of four cultivated and 2,000 accessions of 21 wild species (Loskutov 2001b). For those 90,000 accessions, documentation is easily accessible on the internet. Further, large collections have been mentioned by FAO in Kenya (13,000 accessions), in Israel (7,500 accessions), the latter announcing an especially rich collection of A. sterilis (5,000 accessions), and in Australia (Germeier 2008). In FAO/WIEWS (http://apps3.fao.org/wiews/ germplasm.htm), 29 collections are listed that maintain accessions of wild Avena species (Table 3.3) of which 13 hold more than 20 respective accessions (Brazil, Canada, China, Germany, Israel, Morocco, Norway, Poland, Russia, Spain, Sweden, UK, USA). Some genebanks accumulate specific and geographic diversity of wild oat species not only by means of natural collection but also through seed exchange with and ordering samples from other genebanks (Tables 3.4 and 3.5). This way, they managed to accumulate quite a wide diversity of these species. These genebanks are located in USA, Canada, Russia, Germany, Great Britain, and Poland. Other genebanks, such as those in Australia, Israel, Turkey, Brazil, and some other countries, have the mandate to collect and conserve national biodiversity including wild species that occur in these territories. Therefore, they possess small collections of the species in question. It should be noted that hexaploid species, A. sterilis (A. ludoviciana) and A. fatua, in the first place represent the Table 3.3 Number of accessions of wild oat species in the main genebanks (Germeier 2008) Institution Country Agriculture and Agri-Food Canada, Plant Gene Resources of Canada, Saskatoon Research Center USDA-ARS, National Small Grains Germplasm Research Facility N.I. Vavilov Research Institute of Plant Industry Tel-Aviv University Institute Cereal Crop Development Lieberman Germplasm Bank Agricultural Research Center, Australian Winter Cereals Collection Aegean Agricultural Research Institute, Department of Plant Genetic Resources Institute for Plant Genetics and Crop Plant Research – Genebank National Wheat Research Center National Plant Genetic Resources Center Plant Breeding and Acclimatization Institute Agricultural Research Organization, Volcani Center, Israel Gene Bank for Agricultural Crops Canada USA Russia Israel Australia Turkey Germany Brazil Poland Israel Number of accesions 14,935 10,908 2,001 1,544 549 311 300 254 168 117 AU8 3 Avena Table 3.4 Representation of wild Avena species in ex situ collections in the world (Germeier 2008) Species Number of accessions A. atlantica 18 A. brevis 87 A. canariensis 70 A. damascena 17 A. hirtula 75 A. hispanica 16 A. longiglumis 85 A. nuda 35 A. prostrata 2 A. strigosa 697 A. wiestii 76 A. bruhnsiana 1 A. clauda 111 A. pilosa (syn. A. eriantha) 156 A. ventricosa 8 A. macrostachya 13 A. abyssinica 615 A. barbata 2,526 A. lusitanica 30 A. vaviloviana 248 A. agadiriana 18 A. insularis 14 A. magna (syn. A. moroccana) 97 A. murphyi 12 A. diffusa 8 A. fatua 2,341 A. hybrida 24 A. ludoviciana 444 A. macrocarpa 2 A. occidentalis 71 A. sterilis 22,951 main part of wild oat accessions in the ex situ collections because they are of great importance as breeding material and are easy to conserve and propagate in the field (Table 3.5). Other species, especially the diploid ones, are rare in genebank collections as their natural ranges are narrower, their diversity is sufficiently smaller, and because most of them are difficult to distinguish from each other, and their conservation and propagation are very laborious. In this respect, the Canadian genebank is quite unique with its collection of oat species founded by B. Baum, who has been collecting oats worldwide in the 1970s–1980s (Baum et al. 1975). The American genebank maintains a small collection of diploid and tetraploid species; VIR (Russia) conserves a diverse collection of these species; small collections are also preserved in Germany and Poland. Besides, a small, very carefully composed unique collection of diploid and tetraploid species of oats is conserved in the Welsh Plant Breeding Station, University College of Wales (UK). The base of this collection is seed of Avena wild species obtained during Canada–Wales Expeditions (Rajhathy et al. 1964). Basically, this collection was assembled for research rather than practical purposes for studying cytogenetics and genomic interactions between wild oat species (Leggett 1992a). Genebanks can employ standard methods of ex situ conservation, but organizationally they may differ. Two types of national genebanks exist, the centralized and decentralized ones. Genebanks of the first type unify management of all the plant genetic resource (PGR) activities within one single center (institution), while the stations, where collections are studied and regenerated, can be located elsewhere (Russia, Germany, Canada, etc.). The decentralized genebanks consist of a National PGR Council that coordinates activities of individual institutions and stations where different collections are conserved, studied, and regenerated (USA, France, Spain, etc.). The institutions with a long-standing history of PGR activities belong to the group of centralized genebanks, while the recently established ones, especially those in the West-European countries, belong to the decentralized organizations. United States’ National Plant Germplasm System. Initially in 1898, at the Department of Agriculture of US was established the Section of Seed and Plant Introduction. Later on, the National Plant Germplasm System (NPGS) was organized. It constitutes a coordinated group of scientists from Federal, State, and private sectors of the US agricultural research community. Responsibilities include (1) the acquisition, maintenance, evaluation, enhancement, and distribution of a broad array of germplasm, (2) research on the preservation of genetic diversity and methods of preserving viability through improved storage procedures, and (3) monitoring of genetic vulnerability (Wesenberg et al. 1992). The key elements of the NPGS pertinent to oat include: 1. USDA-ARS Plant Science Institute, Beltsville Agricultural Research Center, Beltsville, MD. This includes the Plant Introduction Office, the Germplasm Services Laboratory, the Germplasm Quality Enhancement Laboratory, and the Systematic Botany and Nematology Laboratory. Included in AU9 Table 3.5 Representation of wild Avena species in the main ex situ collections (Germeier 2008) Genebank atlantica canariensis dama‐ hirtula longi‐ wiestii clauda pilosa ventri‐ macro‐ barbata vavilo‐ agadiriana insularis magna murphyi fatua hybrida ludovi‐ sterilis scena glumis cosa stachya viana ciana Canada USA Russia Australia Germany Poland Israel Turkey Brazil 15 45 3 51 13 45 7 12 46 4 15 2 17 5 9 5 1 10 5 6 7 5 5 1 7 1 91 13 132 4 12 5 1 3 1 1 10 6 6 2 1,685 611 90 40 3 10 32 50 135 43 46 22 14 3 2 34 2 16 2 1 4 4 8 34 1 2 1 3 579 23 1,322 1 219 7 96 1 20 71 1 434 4 11,461 8,246 833 536 65 37 1,500 204 52 I.G. Loskutov and H.W. Rines 3 Avena the Germplasm Services Laboratory is the Germplasm Resources Information Network (GRIN) Database Management Unit. 2. USDA-ARS National Seed Storage Laboratory (NSSL), Fort Collins, CO. The NSSL, established in 1958, is the only long-term storage facility in the US for crop germplasm normally maintained through seed. 3. USDA-ARS National Small Grains Germplasm Research Facility, Aberdeen, ID. The NSGC is housed in the USDA-ARS National Small Grains Germplasm Research Facility that was completed in 1988 at the University of Idaho Aberdeen Research and Extension Center, Aberdeen, ID (Wesenberg et al. 1992). This is main storage for all cereal crops and for cultivated and wild oat too. Nearly one-half of the NSGC oat germplasm consists of wild Avena species, primarily A. sterilis and A. fatua. Since the latter two are hexaploids and can be crossed readily with A. sativa, they are currently the most useful of the related species. Adequate diversity is probably represented in the A. sterilis accessions obtained from Israel, but not from other regions of the world. There is inadequate diversity represented by the accessions available in the NSGC for most other wild species, including some diploids and tetraploids (Wesenberg et al. 1992). GRIN provides National Genetic Resources Program (NGRP) personnel and germplasm users continuous access to databases for the maintenance of passport, characterization, evaluation, inventory, and distribution data important for the effective management and utilization of national germplasm collections (http://www. ars-grin.gov/). Plant Gene Resources of Canada. Agriculture and Agri-Food Canada appointed the first Plant Gene Resources officer and established Plant Gene Resources of Canada (PGRC) in 1970. Until early 1998, it was located at the Central Experimental Farm in Ottawa, but moved to a modern facility in Saskatoon. Canada’s Plant Germplasm System is a network of centers and people dedicated to preserving the genetic diversity of crop plants, their wild relatives, and unique plants in the Canadian biodiversity. The system plays a significant part of Agriculture and Agri-Food Canada’s commitment to the Canadian Biodiveristy Strategy in response to the Convention on Biological Diversity. The largest wild oat collection in the world is located there. A multinodal system was established in 1992 to respond to the recommendations from study committees on the enhancement of germplasm conservation in Canada. It was initially funded through the Green Plan. This initiative links rejuvenation, evaluation, and documentation to research and plant breeding programs for specific crop plants. Seed storage facilities at PGRC consist of long-term, medium-term and cryopreservation units. For long-term storage, a large walk-in vault is available in which seed is preserved in laminated envelopes at 20 C. For medium-term storage, a large walk-in vault stores seed in paper envelopes at 4 C and 20% relative humidity. Seeds are evaluated for viability, dried to optimum moisture content of 6–8% and transferred to either medium- or long-term storage. Cryopreservation (a type of freezing) in or over liquid nitrogen at 196 C is the most highly developed of these techniques. Depending on the species, dry seeds can last from a few years to probably centuries (http:// pgrc3.agr.gc.ca/index_e.html). Vavilov Institute of Plant Industry – VIR (Russia) originated and developed from the Bureau of Applied Botany organized in 1894; in 1930, it was named the All-Union Research Institute of Plant Industry (VIR – Russian abbreviation), and since 1967, it has borne the name of N.I. Vavilov. The main directions in the work of the Institute were determined by N.I. Vavilov to be collecting, conserving, studying, and utilizing plant genetic resources. Besides, the Institute is involved in designing methods for studying collection materials and developing various long-term conservation techniques. The Vavilov Institute of Plant Industry is governed by the administration (located in St. Petersburg) that supervises and coordinates activities of the entire institute and experiment stations, including nine departments of crop genetic resources, the Department of Agrobotany, and In Situ Conservation with a unique herbarium collection, ten departments and laboratories dealing with methodology of PGR studies, a genebank consisting of several storage facilities (ensuring PGR conservation at þ4 C, 10 C, 18 C and cryoconservation), and the Department of Biotechnology that includes an in vitro conservation unit. The network of the Institute also includes 11 experimental stations for PGR studies and regeneration, and the I.G. Loskutov and H.W. Rines National Seed Store at Kuban Experiment Station (þ4 C, 10 C, 18 C). On the VIR website, more information about Institute’s activity and passport database of VIR collection is available (http://vir.nw.ru/data/dbf.htm). VIR collection of cultivated and wild oat is maintained in the Department of Genetic Resources of oat, barley, and rye. All information about taxonomy, characterization, evaluation, and breeding value of cultivated and wild species collection is available on their Avena webpage (http://vir.nw.ru/avena/). Coordination activities of national genebanks are fulfilled by international organizations. The International Board for Plant Genetic Resources (IBPGR) was established in 1974 to create and coordinate a worldwide network of germplasm resource conservation centers. The IBPGR receives funds from the World Bank, the Food and Agriculture Organization of the United Nations (FAO), the United Nations Development Program, and individual donor nations. Like other international centers for agricultural research, the IBPGR is under the jurisdiction of the Consultative Group on International Agricultural Research (CGIAR), established in 1971. The Board’s Secretariat, responsible for collecting and documenting information and administering the Board’s financial program, is provided by the FAO in Rome. The IBPGR has been effective in assisting various international, regional, and national research centers in acquiring, multiplying, storing, documenting, evaluating, and distributing germplasm. The IBPGR or its designees have established a set of descriptors for many crop species, organized and sponsored collection expeditions, and designated specific locations as repositories for the world’s base collections for seed of principal food crops. In 1991, IBPGR was renamed as International Plant Genetic Recourses Institute (IPGRI). IPGRI is an autonomous international scientific organization, supported by the CGIAR. Mandate of the Institute is to advance the conservation and use of plant genetic resources for the benefit of present and future generations. In 2006, IPGRI and the International Network for the Improvement of Banana and Plantain (INIBAP) became a single organization under new name Bioversity International (http://www. bioversityinternational.org). Collection centers participate in national, regional, and global networks. National networks in many cases organize the national plans and responsibilities on genetic resources and often have to coordinate a multitude of institutions working in the sector. Important regional networks are the ECP/GR on the European level and related activities as EURISCO and the Central Crop Database. Information networking in the Nordic countries is affiliated with SESTO, a genebank management tool developed by the Nordic Gene Bank. In South America, some networking has been mentioned around the software product DBGermo. Global networks cover breeding interests, such as the Quaker nursery and a Uniform Oat Winter Hardiness Nursery, the FAO World Information and Early Warning System (WIEWS), and several international information projects such as the Global Biodiversity Information Facility (GBIF) and the Pedigree of Oatlines (POOL) database. Though GRIN is a national product of the USDA, it is of global relevance and is also used by Canada, and thus considered as an international network. A large part of networking focuses on information and documentation issues (Germeier 2008). The Working Group on Avena was set up in 1984 with the task of coordinating the work on oat genetic resources in Europe (IBPGR 1984). The Group unites oat collection curators from all European genebanks. The Working Group coordinates activities aimed at collecting, documenting, studying, conserving, and utilizing oat genetic resources. A large part of networking focuses on information and documentation issues through Avena Database (http://eadb.bafz.de/ bgrc/eadb/avena.htm). Periodically, the Group convenes its meetings to discuss the most important questions related to genebank activities (IBPGR 1986, 1989; Frison et al. 1993; Maggioni et al. 1998). At present, the Avena Working Group operates within the ECPGR Cereals Network that coordinates the work on genetic resources of all cereal crops in the European territory as well as that performed by the institutions holding significant cereal collections in some Asian and African countries (Lipman et al. 2005; Maggioni et al. 2009) (http://www.ecpgr.cgiar.org/Workgroups/ avena/avena.htm). At present, genebanks and international organizations involved in activities targeted at oat genetic resources conservation successfully perform and coordinate this work aimed at rational and effective utilization of oat species in breeding programs. 3 Avena 3.2.4 Modes of Preservation and Maintenance: Seeds/Propagule/ Cryopreservation The limited amount of genetic variation for vegetatively propagated species has led to efforts to develop in vitro conservation methods. It guarantees freedom from pest infestation and diseases. However, it is extremely laborious and cost intensive and can therefore only be used for special material as a long-term storage possibility (Hammer and Teklu 2008). Cryoconservation is accomplished with liquid nitrogen at 196 C. It is also suitable for seeds and leads to a dramatic prolongation of germination rates. It allows for an extremely long storage of many species. The problem with cryoconservation is its high cost, especially for technical equipment. A constant supply of liquid nitrogen also has to be available at all times (Hammer and Teklu 2008). In regard to seeds of wild oat species, some experimental work concerning their cryoconservation was carried out at VIR (Russia) in the 1970s–1980s but was terminated later, as the procedure for seeds of this type turned out to be unjustifiably expensive in comparison with conservation under different storage regimes ensuring good germinating ability of oat seeds for a long period. 3.3 Role in Elucidation of Origin and Evolution of Allied Crop Plants Combined field studies performed in the late 1950s and early 1960s in the regions of the origin and maximum diversity of oat species Avena (Baum et al. 1972a, b; Rajhathy et al. 1964, 1966) drew attention of the researchers to the karyology and cytogenetics of cultivated oat species and their wild relatives. This added to understanding the mechanisms responsible for reproductive isolation of the species. Since the 1950s, the investigation of wild and cultivated oat species has involved interspecific crosses conducted for various purposes (Rajhathy and Thomas 1974). The theoretical objective of these studies was to establish the diploid ancestor of cultivated hexaploid oat, which, in turn, would add to understanding the cytogenetics of this species and clarify its genomic formula and pathway of evolution. One of the first studies concerning the genomic formula of cultivated oat was performed by Nishiyama (1929), who crossed A. sativa and A. strigosa. In later experiments, crosses of A. strigosa with the diploid species A. hirtula and A. wiestii produced fertile offsprings, and their chromosomes were completely homeologous. This suggested that these species belong to one group having the same genome, thereby confirming Malzev’s (1930) suggestion on close relatedness of these forms, which he assigned to one species A. strigosa. It was found that these species are identical in chromosome structure because their hybrids regularly formed seven bivalents (Rajhathy 1966). The diploid species A. atlantica was crossed with A. strigosa and other species of this group and gave fertile progeny. On this ground, some authors regarded A. atlantica as a wild analog of A. strigosa instead of A. hirtula (Rajhathy and Morrison 1959). Other diploid species having chromosome variants of the A genome [A. canariensis (Ac), A. damascena (Ad), A. prostrata (Ap), and A. longiglumis (Al)] differ by the results of hybridization: A. prostrata is quite compatible with all the listed species, and A. longiglumis is readily crossable with A. strigosa, whereas hybrids between A. canariensis and A. damascenа are sterile (Rajhathy and Morrison 1959; Rajhathy 1961; Rajhathy and Baum 1972; Baum et al. 1973; Ladizinsky 1973a; Leggett 1984, 1987). On the other hand, A. strigosa, A. hirtula, A. wiestii, and A. atlantica have similar karyotype and are interfertile. A. lusitanica, A. hispanica, and A. matritensis have been demonstrated to be homologous to A. strigosa according to results of DNA in situ hybridization. A. longiglumis and A. prostrata are more related to each other than to A. strigosa, from which they differ by at least five chromosome rearrangements. A. damascena and A. canariensis are separate from A. strigosa with at least three translocations; a larger one is in A. canariensis and assume a common progenitor for A. damascena, A. canariensis, and A. prostrata (Jellen and Leggett 2006). Crosses of the diploid species A. pilosa with cultivated oat revealed partial chromosome homeology for one of these species genomes. A high or I.G. Loskutov and H.W. Rines complete homeology was revealed in crosses between the A genome diploid species and hexaploid species. However, these species are incompatible in crosses with A. pilosa. It was thus concluded that A. pilosa has a variant of the C genome (Rajhathy 1966). Species with the C genome are readily crossed with each other and their hybrids form seven bivalents. At the same time, no interspecific hybrids were obtained between the species with the genomic formulas A and C. The species A. ventricosa was generally used in such studies as the donor of the C genome (Rajhathy and Thomas 1967). The natural habitat of this species (Algeria and Cyprus) is completely isolated from those of species with the A genome, which confirms their incompatibility. The scarcity of bivalents in the meiosis of the A. strigosa  A. pilosa hybrid carrying the A and C genomes confirmed the significant difference between these genomes (Nishiyama and Yabuno 1975). The results of cytogenetic studies of C genome species are consistent with the suggestion by Malzev (1930), who pointed to a significant difference in the ecology and morphology of these taxa and recognized two groups of diploid species, A. pilosa, A. clauda and A. ventricosa, A. bruhnsiana. The species of the former group gave fertile offspring in crosses with each other (Rajhathy and Thomas 1967; Nishiyama and Yabuno 1975) and demonstrated reproductive isolation in crosses with the species of the latter group. Interspecific crosses between diploid species and species with other ploidy levels demonstrated that the A genome could have been originated from A. strigosa and A. longiglumis (Rajhathy 1971a) or A. canariensis (Baum et al. 1973). Only partial homeology was revealed between the chromosomes of A-genome diploids and those of cultivated oat (Rajhathy and Thomas 1974). The morphological traits of A. canariensis suggested that it could have been the progenitor of tetraploid and hexaploid species (Baum et al. 1973), but cytological studies did not reveal complete homeology between their chromosomes (Leggett 1980). Afterwards the A genome developed independently from the C genome, which brought about lots of A genome variants (Al, Ap, Ad, Ac, As), and finally produced a cultivated diploid species (A. strigosa) with the As genome (Loskutov 2008). On the basis of ample factual evidence, it was suggested that A. ventricosa could have been the diploid donor of the C genome for tetraploid and hexaploid species (Rajhathy 1966). All tetraploid species can be classified into four groups based on their karyotypes, morphology, and the pattern of chromosome conjugation in meiosis of interspecific hybrids. Group 1 includes A. barbata, A. vaviloviana, and A. аbyssinica. They are genetically uniform and possess the AB genome. Their relationships were later confirmed by the fact that the tetraploid species of this group are autotetraploids, which originated from the diploid species A. hirtula and A. wiestii (Holden 1966; Ladizinsky and Zohary 1968; Sadasivaiah and Rajhathy 1968). The AB genome was suggested to have resulted from the divergence of the original diploid A genome (Rajhathy and Thomas 1974). In recent studies, it is designated as AA0 (Fabijanski et al. 1990). These species are readily crossable with all species of the genus Avena, except for diploids with the C genome (Leggett and Markland 1995). Both tetraploid species from this group A. vaviloviana and A. abyssinica, having found in Ethiopia the most favorable climate and soil conditions for distribution into the south of the Mediterranean center, were unable to move further because of more severe arid climate in the countries adjacent to Ethiopia. It should be mentioned that diploid and hexaploid cultivated species incorporate naked forms, while tetraploids do not contain them. The most probable reason for that, in our opinion, is that the species of this group were unable to disperse far from their center of origin and had no recessive mutations (Loskutov 2008). The species with A and AB (AA0 ) genomes and a biaristulate lemma tip in most cases each floret disarticulated. Some of them have cultivated analog with the same ploidy level (A. wiestii, A. hirtula – A. strigosa; A. vaviloviana – A. abyssinica) and wider areas of distribution (A. wiestii, A. hirtula, A. barbata, etc.) being rather active weeds. Obviously, this group apparently had no part in the development of hexaploid oats (Loskutov 2008). Group 2 includes A. magna and A. murphyi. Crossing of diploid species possessing the As genome with A. magna gave partially sterile hybrids (Leggett 1987). Cytological examination of the F1 hybrids from A. barbata  A. magna showed that these species are not related. Crosses A. sativa  A. magna also yielded sterile F1 hybrids (Thomas 1988). The great morphological similarity between A. magna and wild hexaploids and the meiotic pattern of pentaploid hybrids obtained with the use of A. sativa suggested that AU10 3 Avena A. magna could have been involved in the evolution of hexaploid species as an AC tetraploid progenitor (Ladizinsky and Zohary 1971). Reciprocal crosses of A. magna with cultivated oat and other hexaploid species demonstrated its important role in the evolution of hexaploid species (Ladizinsky 1988). The results of interspecific crosses brought some scientists to the conclusion that the tetraploids bearing the AC genomes originated from diploid species bearing its components, presumably A. canariensis (A) and A. ventricosa (C). According to an alternative opinion, the A genomes of A. magna and A. strigosa were identical, and the C genomes of A. magna and A. pilosa were related. However, later, this hypothesis was discarded (Leggett and Markland 1995; Leggett 1998). Group 3 of tetraploids includes A. macrostachya, which is a perennial outcrossing autotetraploid. According to Malzev’s (1930) definition for the genus Avena, the morphological features of this species allow it to be assigned to the most primitive oat-grasses. Crosses of this species with diploids possessing various derivatives of the A genome (A. damascena, A. prostrata, A. atlantica, and A. canariensis) demonstrate negligible chromosome homeology (Leggett 1985, 1992b). According to other studies, the most viable F1 hybrids were obtained between A. pilosa and A. macrostachya. They often form trivalents in the metaphase. Hybrids between A. atlantica and A. prostrata formed seven bivalents each (Pohler and Hoppe 1991). The mitosis study of crosses A. barbata  A. macrostachya suggested autotetraploid origin of the latter and the close relatedness of the species, although the hybrids were sterile even after chromosome duplication by colchicine (Hoppe and Pohler 1989). The apparent differences in the morphology of A. macrostachya and a low percentage of chromosome conjugation in the meiosis of hybrids of A. macrostachya with A. sativa and A. murphyi indicate that A. macrostachya was not involved in the evolution of tetraploid or hexaploid species (Leggett 1985). Further studies demonstrated that the A. macrostachya genome is closer to the C (A. pilosa) genome than to the A (A. strigosa) one (Leggett 1990). A. macrostachya is considered as more related to the C-genome than the A-genome diploids and the situation may be complicated by the operation of a pairing control gene in the species (Jellen and Leggett 2006). It is the only autotetraploid species within the genus Avena (Rodionov et al. 2005), while all other tetraploid species are a result of hybridization of different diploid progenitors (Badaeva et al. 2005). Meanwhile, according to Rodionov et al. (2005), the division of the phylogenetic oat lines carrying A and C genomes was accompanied by accumulation of differences in dispersed repeat sequences and accumulation of transitions and transversions specific for each branch. Later, the C-genome line segregated into phylogenetic branches of A. macrostachya from the progenitor of the other species with the C genome, and after that, the progenitors of A. macrostachya doubled their chromosome number and generated large blocks of C-heterochromatin that resulted in characteristic C-banding pattern of A. macrostachya chromosomes. Group 4, including A. agadiriana, cannot be considered as independent since this species is little studied. A. agadiriana was discovered by finding tetraploid forms in collections of the diploid species A. canariensis rather than discovering it in nature. Later, it was found that these species have different natural habitats: the diploid A. canariensis is endemic to Canary Islands (Spain) and the tetraploid A. agadiriana occurs only in Morocco (Baum and Fedak 1985a, b). Nevertheless, it is believed that the latter is more closely related to A. barbata than any other tetraploid species and has the AB genome composition (Leggett 1988). Moreover, A. agadiriana is similar to A. magna, A. murphyi, and other hexaploids in the structure of lodicules, forms of lemma tips, etc. The participation of A. agadiriana in the evolution of hexaploids is indicated by the above evidence and by the good crossability between hexaploids and this species (Thomas 1988; Alicchio et al. 1995). Interspecific crosses were also used for determining the genomic constitution of the most important group of hexaploids. Crosses of diploid species having the As genome (A. strigosa group) and tetraploid species having the AB genome with A. sativa demonstrated that the hexaploid species has the A genome but lacks the B genome. In later studies, the A and C genomes were found to be similar to the corresponding genomes of diploids and tetraploids, whereas the origin of the D genome is still unknown (Rajhathy and Thomas 1974). The following evolutionary pathway was proposed: A. canariensis > A. magna > A. sterilis (Baum et al. 1973). Later, the A genomes of A. magna and A. sterilis proved to be closer to each other than the AU11 I.G. Loskutov and H.W. Rines A genomes of A. abyssinica and A. sativa. It was suggested that A. magna was the donor of two genomes (AC) of the hexaploid Avena species (Thomas 1988). Later, it was found that the genomes A and D are similar to each other but different from C (Leggett and Markland 1995). The A genome of the diploid progenitor appears to have been the ancestor of the A and D genomes of hexaploid species (Linares et al. 1996). Recent studies have demonstrated that the D genome is likely to be a variant of the “A” genome, like the B genome, but differs from the latter (Leggett 1997). On the other hand, Katsiotis et al. (2000) reported on repetitive DNA elements common to Arrhenatherum and the Avena A genome that were either absent, less abundant, or polymorphic in the C genome of Avena. A new tetraploid species, A. insularis, has been recently reported in 1998. It was suggested to be one of the progenitors of the hexaploid species and is tentatively assumed to have the CD or CA genome. This species gave fertile hybrids with A. strigosa only. With closely related A. magna and A. murphyi, the hybrids were sterile and partially fertile hybrids are obtained with hexaploid species (Ladizinsky 1999). Species with C and AC genomes (A. ventricosa, A. canariensis, A. magna, A. murphyi, A. insularis) are considered as transitional progenitor forms in the evolution of hexaploid oats (Fig. 3.1). Some of these species are strictly endemic or have a very limited area of distribution as wild representatives of natural undisturbed habitats. There are no other (direct) cultivated analogs of these species. Together with the cultivated forms, these species are classified into a section Avenae (Loskutov 2008). In Avena, areas of domestication seem not to coincide with the primary areas of distribution or the centers of origin of the weed progenitors (Vavilov 1965a, 1992). Malzev (1930) located the origin of the hexaploid oat in Southwest Asia region. Baum (1972) considered A. septentrionalis (¼ A. hybrida) as the closest progenitor to the cultivated oat. It is distributed in Mongolia to the Ural links the European center with the Chinese centers of diversity of cultivated oats (Holden 1979; Thomas 1995). The species A. sterilis is a more likely hexaploid progenitor of cultivated oat than A. fatua (Zhou et al. 1999; Jellen and Beard 2000). It is suggested that large-seeded A. sterilis, disarticulated by separate spikelets, underwent mutations in the type of floret dispersal, which led to the development of the cultivated species A. byzantina, and on the other hand, of the wild species A. occidentalis shattering by separate florets and occurring presently only on the Canary Isles (Spain). It is highly probable that, owing to the changes in the disarticulation type, A. occidentalis had previously occupied vast areas; besides, its dominating type of development is winter or semi-winter, and we consider it as primary, compared to the spring type. In the process of eastward distribution, A. sterilis became differentiated into more adaptive smallseeded forms of A. ludoviciana, which underwent mutations in the Minor Asiatic center that changed their florets’ disarticulation type. It led, in turn, to the appearance of weedy forms of A. sativa. As for A. occidentalis, when moving eastwards, it acquired earlier-ripening, typically spring forms, which combined into a separate species, A. fatua (may be included A. hybrida). This species, disarticulating by separate florets, became a harmful weed and infested vast areas in the north and east of Europe and Asia. Weak sensitivity to vernalization and strong reaction to the length of day was reported to indicate true spring nature of A. fatua, which enabled it to occupy by weeding the most extensive agricultural territories on Earth. True spring nature of this species proves that it was secondary in origin as compared with A. sterilis and A. ludoviciana (Loskutov 2007). The ample evidence on interspecific crosses and other researches suggest that the evolution of the genus Avena involved two strikingly different genomes: A and C. Other genomes were their more or less distant derivatives. According to the generally adopted assumption that the diploid species A. canariensis and A. ventricosa are the progenitors of the A and C genomes, respectively, the evolution of the resulting allopolyploids should have involved structural chromosome rearrangements, making them partially homeologous. 3.3.1 List of Related Crop Plants The cultivated hexaploid common oat ranks fifth among cereals in world production. Oats are coolseason crop, and while they are grown to some extent on every continent, their production is of far greater importance in the cool climate of the northern hemisphere. 3 Avena ssp.nudibrevis ssp.nudisativa A.occidentalis - ACD A.vaviloviana-AB A.sativa - ACD A.barbata - AB A.hirtula - As A.agadiriana – AB? A.wiestii - As A.ludoviciana - ACD A.murphyi - AC A.byzantina - ACD A.sterilis - ACD A.strigosa-As A.magna - AC A.canariensis - Ac A.atlantica - As A.insularis–CD? A.clauda - Cp A.bruhnsiana - Cv A.pilosa - Cp A.prostrata - Ap A.ventricosa - Cv A.damascena - Ad A.longiglumis - Al Avenastrum - evolution pathways of the species and forms - probable evolution pathway of hexaploid cultivated species Fig. 3.1 Phylogenetic relationships of Avena species (Loskutov 2008). Thin arrow: evolution pathways of the species and forms, bold arrow: probable evolution pathway of hexaploid cultivated species Avena is a polyploid series from diploid through tetraploid to hexaploid. There are cultivated forms at each ploidy level: the common oat (A. sativa, 2n ¼ 6x ¼ 42), the red oat (A. byzantina, 2n ¼ 6x ¼ 42), the Ethiopian oat (A. abyssinica, 2n ¼ 4x ¼ 28), and the sandy oat (A. strigosa, 2n ¼ 2x ¼ 14). The whole diversity of cultivated oats was proven by N. I. Vavilov (1926) to have a weedy field origin. As its species moved northwards, oat replaced basic crops by weeding them and became an independent crop for itself. This process may be clearly traced in Spain on the cultivated diploid species A. strigosa, in Ethiopia on A. abyssinica, in Turkey and Iran on A. byzantina, and in Iran and Russia on A. sativa (Fig. 3.2). The main difference between wild species and cultivated ones is disarticulation of the florets. All cultivated species have non-shattering panicle, mostly glabrous lemma and soft awn if it existed. Very high distribution of cultivated, especially hexaploid, species through the whole world is a reason for their high diversity (Loskutov 2008). The hexaploid cultivated species A. sativa occurs in all agricultural regions of the world with moderate climate; it is cultivated in all European countries including Russia, in the north of the Asian continent, above the 30th parallel, in the North American countries, in the northern and southern parts of South America, at the southern tip of Africa, in New Zealand, and Australia. This species is represented by both hulled (A. sativa subsp. sativa L.) and naked forms (A. sativa subsp. nudisativa (Husnot.) Rod. et Sold.) (Rodionova et al. 1994), which, to all appearance, have originated in China (Loskutov 2008) (Fig. 3.2). The species A. byzantina has a more limited natural habitat and is characterized by a higher degree of drought tolerance. It is cultivated in countries of Southern Europe, in northern Africa, in Southwest Asia above the 30th parallel, and in some South American countries. Under cultivation, this species is represented by hulled form only [A. byzantina (С. Koch) Thell.], while the existence of a naked form [A. byzantina subsp. denudate (Hausskn.) Rod. et Sold.] has been This figure will be printed in b/w A.fatua - ACD A.abyssinica -AB I.G. Loskutov and H.W. Rines subsp. nudibrevis 3 A. sativa 6 A. strigosa subs. nudisativa 2 A. sativa 7 A. byzantina subs. denudata 5 A. abyssinica 4 1. Mediterranean centre – Morocco, Algeria, Spain 5. South-West Asian centre – Turkey, Iran, Iraq, Syria 2. Spain and Portugal – centre of diversity of A. strigosa 6. Tatarstan, Bashkortostan – diversity of A. sativa convar. volgensis 3. Great Britain – centre of diversity of A. strigosa subsp. nudibrevis 7. China, Mongolia – centre of diversity of A. sativa subsp.nudisativa 4. Abyssinian centre – Ethiopia, centre of diversity of A. abyssinica - pathways of distribution of cultivated species and forms. Fig. 3.2 Evolution pathways of cultivated Avena species (Loskutov 2008) identified by Malzev (1930) and mentioned by Rodionova et al. (1994). Recently, it has also been newly described and confirmed of Turkish origin (Loskutov 2007) (Fig. 3.2). It should be noted that the majority of modern oat cultivars widely spread in Southern Europe, Asia, Africa, America, and Australia have originated as hybrids of A. sativa and A. byzantina with an intermediate manifestation of many morphological traits. A. abyssinica is a tetraploid species typical of Ethiopia, which had progressed northwards to more humid regions, crowded out other cereal crops (e.g., barley), and had become a cultivated plant. In the south of the country, it is an ordinary segetal weed in spelt and barley fields (Vavilov 1965b, 1992). Most likely, the species has not developed naked forms because of the narrowness of its natural range. The diploid A. strigosa has been quite widely cultivated for forage and hay before Second World War in many countries of northern and Central Europe as well as in the European Russia. At present, this species is a ruderal weed in Southern Europe and in some places is cultivated for non-commercial use (Fig. 3.2). At the same time, such commercial cultivars of this species as Saia, Saia 2, Saia 4, Saia 6, etc. have been bred in Brazil through selection from local populations and are cultivated quite widely in South America. In the nature and majority of collections, this species is represented by hulled forms (A. strigosa subsp. strigosa Thell. and A. strigosa subsp. brevis Husn.), which, most likely, have originated from Spain, but sometimes unique naked forms originating from the mountainous regions of Great Britain may be found, which had been described by Linneaus (1762) as A. nuda L. In the beginning of the twentieth century, the name A. nuda L. started to be used for the naked forms of diploid cultivated oats, while the diploid forms were given the name A. nudibrevis Vav. In the 1970s, B. Baum (1977) restored the initial name A. nuda L. to the diploid naked forms, but the hexaploid naked forms were not determined in this taxonomy. On the other hand, it has been proved long ago that the diploid naked forms are easily crossed with the hulled forms of A. strigosa Schreb., and this pair has much in common concerning the majority of morphological traits. This figure will be printed in b/w A. byzantina 1 AU12 3 Avena According to Rodionova et al. (1994), these naked forms belong to the sandy oat subspecies A. strigosa subsp. nudibrevis (Vav.) Kobyl. et Rod. Thus, the genus Avena includes four cultivated species, which had been quite widely used in agriculture of different countries of the Old World, while at present only cultivated hexaploid oat species keep leading positions in the world in terms of the occupied areas. 3.3.2 Application of Morpho-taxonomy Classification based primarily on morphological traits is the fundamental basis for botanical research. There is no agreement among researchers regarding the systematics of the species in Avena L. The history of taxonomy of this genus started about 300 years ago (Linneaus 1762, 1753). Among the numerous publications of the nineteenth century dedicated to the systematics of Avena L., the most significant taxonomic surveys were by Marshall Bieberstein (1819), Grisebach (1844), Koch (1848), and Cosson and Durie de Maisonneuve (1855). Natural or phylogenetic classifications that outlined groups of related species and derived cultivated species from wild ones were developed later (Jessen 1863; Haussknecht 1885). Similar views on the polyphyletic origin of oats were shared by other researchers (Trabut 1909, 1914; Thellung 1911, 1919, 1928; Zade 1918). The most detailed classification of this very important genus of Mediterranean origin was developed by Malzev (1930) and remains the most cited Avena monograph based on the main morphological characters – rachilla and lemma tip shape, lemma pubescence, and the disarticulation of florets. Many assumptions concerning the position of a number of species were made by him on the basis of analysis of a complex of morphological and biological characteristics. Malzev produced the most comprehensive phylogenetic system of the type section of this genus based on lemma tip characteristics by dividing it into two subsections and by analyzing all wild species known at that time. According to Malzev (1930), Avena includes 7 species represented by 22 subspecies and 184 recognizable groups within subspecies (varieties and forms). The work of Malzev drew heavily on that of Thellung (1928). Malzev made a thorough analysis of Avena based on the major classification principles dominating at that time, where subspecies was an important taxonomic unit (Table 3.6). Further development of a natural classification for the genus resulted from explorations of Vavilov (1926, 1927, 1992), Nevski (1934), and Mordvinkina (1936). For the detailed structured systems of the genus, the authors used morphological characteristics and plant immunological data for species and subspecific taxa, genetic and cytological data, and new information on the natural habitats for each species. The system of Mordvinkina (1936) supplemented by genetic, karyological, and morphological data with the addition of newly described species served as a foundation for the development of classification of Avena L. suggested by Rodionova et al. (1994). In the second part of the twentieth century, several classifications of Avena L. were developed, for example, by Sampson (1954), Stanton (1955), Mansfeld (1958), Coffman (1961), and Romero Zarco (1996). Two tendencies are obvious in the modern classifications of Avena (1) a decrease in number of species due to lumping based on karyological observations only, and (2) an increase in the number of species and subdivisions of species into smaller ones on the basis of morphological differences. Extreme examples of these trends are such classifications where the number of Avena species is either only 7 (Ladizinsky and Zohary 1971) and 14 (Ladizinsky 1988) or 34 (Baum 1977). In the first case, one can see unjustified lumping of species based only on karyological data disregarding their natural habitats. Ladizinsky (1989) combined the whole diversity of oat forms in a number of composite (14), so-called biological species (A. ventricosa Bal ex Coss., A. clauda Dur., A. longiglumis Dur., A. prostrata Ladiz., A. damascena Rajhat. et Baum, A. strigosa Schreb., A. atlantica Baum et Fedak., A. canariensis Baum, Raj. et Samp., A. macrostachya Bal. ex Coss. et Dur., A. barbata Pott. ex Link, A. agadiriana Baum et Fedak, A. magna Murphy et Terrell., A. murphyi Ladiz., A. sativa L.). The remaining species are defined by him as taxonomic species and are incorporated in the former ones without being divided into cultivated and wild forms. In the second case, the rank of species is attributed to hybrid species, forms, and mutants, which evolve quite frequently. In his researches, Baum (1974) employed a formal approach based on the analysis of I.G. Loskutov and H.W. Rines Table 3.6 Taxonomic system of section Euavena Griseb. of genus Avena L. (Malzev 1930) Subsection Seria Species Subspecies Aristulatae Malz. Inaequaliglumis Malz. A. clauda Dur. A. pilosa M. B. Stipitae Malz. A. longiglumis Dur. A. ventricosa Balan. ventricosa (Balan) Malz. bruhnsiana (Grun.) Malz. Eubarbatae Malz. A. strigosa Schreb. strigosa (Schreb.) Thell. hirtula (Lagas.) Malz. barbata (Pott) Thell. wiestii (Steud.) Thell. vaviloviana Malz. abyssinica (Hochst.) Thell. Denticulatae Malz. A. fatua L. septentrionalis Malz. nodipilosa Malz. meridionalis Malz. macrantha (Hack.) Malz. fatua (L.) Thell. sativa (L.) Thell. cultiformis Malz. praegravis (Kraus.) Malz. A. sterilis L. ludoviciana (Dur.) Gill. et Magn. pseudo-sativa Thell. trichophylla (C. K. et Hausskn.) Malz. nodipubescens Malz. macrocarpa (Monch.) Briq. byzantina (C. K.) Thell. AU14 variability of 27 characters by taximetric methods. Among the most significant characters, he used the shape (type) of lodicules and epiblast as well as the ploidy level of the species. Both tendencies may prevent practical application of such taxonomic systems. Baum has analyzed a very wide variety of oat materials including more than 10,000 herbarium sheets, 5,000 accessions of field evaluation, and 5,000 collected accessions of wild species. On the basis of this exploration and evaluation, the genus Avena L. was divided into 7 sections and 34 species (Baum 1977; Table 3.7). Summarized taxonomy of Malzev (1930), Mordvinkina (1936), and Rodionova et al. (1994) and based on the recent literature concerning the oats and on the evaluation of the 26 species, VIR world collection of the genus Avena L. under field conditions and different laboratory methods were confirmed. The genus is divided up into two sections of subgenus Avena: Aristulatae (Malz.) Losk. and Avenae Losk. Perennial outcrossing autotetraploid A. macrostachya belongs to subgenus Avenastrum (C. Koch) Losk. On the basis of a detailed morphology (presence of bidentate or bisubulate lemma tip), distribution, and ecology (most of them true wild, not weedy species), we concluded that diploids and tetraploids of Avenae section were involved in the evolution of hexaploid wild and cultivated oats (Loskutov 2007; Tables 3.8 and 3.9). A consideration of different taxonomic systems based predominantly on morphological traits shows that these systems can substantially differ from each other depending on the keystone character. 3.3.3 Application of Biochemical and Molecular Markers Morphological studies do not offer a complete understanding of the evolutionary and systematic position of some oat species and forms. There is no universal molecular approach for many of the problems faced by taxonomists and genebank managers, and many AU13 3 Avena Table 3.7 Taxonomic system of species of genus Avena L. (Baum 1977) Section Species Avenatrichon (Holub) A. macrostachya Bal. ex Coss. et Baum Dur. Ventricosa Baum A. clauda Dur. A. eriantha Dur. A. ventricosa Bal. ex Coss. A. clauda  eriantha F1 hybrid Agraria Baum A. brevis Roth A. hispanica Ard. A. nuda L. A. strigosa Schreb. Tenuicarpa Baum A. barbata Pott ex Link A. canariensis Baum, Rajh. et Samp. A. damascena Rajh. eBaum A. hirtula Lag. A. longiglumis Dur. A. lusitanica Baum A. matritensis Baum A. wiestii Steud. A. lusitanica  longiglumis F1 hybrid Ethiopica Baum A. abyssinica Hochst. A. vaviloviana (Malz.) Mordv. A. abyssinica  vaviloviana F1 hybrid Pachycarpa Baum A. maroccana Gdgr. A. murphyi Ladiz. Avena Baum A. atherantha Presl. A. fatua L. A. hybrida Peterm. A. occidentalis Dur. A. sativa L. A. sterilis L. A. trichophylla C. Koch techniques complement each other. However, some techniques are clearly more appropriate than others for some specific applications. In an ideal situation, the most appropriate marker(s) can be chosen irrespective of time or funding constraints, but in other cases, the choice of marker(s) will depend on constraints of equipment or funds (Spooner et al. 2005). The use of protein markers helps to sufficiently accelerate the works on specifying genomic composition of diploid and allopolyploid species, establishing phylogenetic relations between the species and clarifying some aspects of intraspecific diversity. The application of molecular markers, proteins and DNA, has offered possibilities for solving a series of theoretical problems related to plant phylogeny and taxonomy. The use of protein markers permits successful identification of genetic resources and registration when solving different problems related to classification of cultivated plants and their wild relatives. A study of protein markers of the cultivated hexaploid oat A. sativa, cultivated diploid species A. strigosa, and wild A. ventricosa has shown that out of ten bands identified in electrophoretic banding patterns of A. sativa, seven were found in A. strigosa and six in A. ventricosa. At the same time, two components identified in the latter species were missing in A. strigosa, while another found in A. sativa has not been discovered in any diploid species. Presumably, this component can characterize the D genome of hexaploid species (Thomas and Jones 1968). Electrophoretic banding patterns have demonstrated that the Cp genome of diploid species probably represents the modified Cv genome, that the C- and A-genome species have very different avenin patterns, that tetraploid species have demonstrated sufficient diversity of this trait, and that all the studied hexaploids had the most monomorphic patterns (Murray et al. 1970). Later, it was determined that diploid species with the A-genome types had different patterns, while those with the C-genome types were similar to each other. All the AB-genome tetraploid species were found to be monomorphic. Both hexaploid species and individual hexaploid accessions were mostly uniform, in comparison with other studied accessions. At the same time, all hexaploids species and only one tetraploid species A. magna (AC genome) were found to have identical bands, indicating their systematic affinity (Lookhart and Pomeranz 1985). Comparative uniformity of electrophoretic banding patterns of the AB-genome tetraploid species proves their autotetraploid nature. In addition to affinity of the AC-genome species, closeness of the As-genome diploids to hexaploid oat species has also been proved (Ladizinsky and Johnson 1972). A study of two subspecies, A. sterilis subsp. ludoviciana and A. sterilis subsp. macrocarpa from Spain, has shown them to significantly differ from one another in terms of intensity of electrophoretic banding patterns (Cadahia and Garcia-Baudin 1978). Out of the total of 34 bands identified in electrophoretic banding patterns, wild diploid species of Avena were found to contain 15 bands, tetraploid 16 and hexaploid 17, on the average. The presence of only 11–13 bands are characteristic of the C-genome (except A. bruhnsiana), as well as Ap- and Ad-genome AU15 Table 3.8 Key for the identification of Avena species (Loskutov 2007) 1. Perennial plants . . . . . . . . . . . . . . . . . . . . . . . . . . . A. macrostachya Balan. Annual plants 2. Lemma tips biaristulate Lemma tips bidentate or bisubulate 3. Glumes very unequal, lower glume one-half of upper one Glumes equal or nearly so 4. Disarticulate each floret at maturity . . . . . . . . . . . . . . . . . . . . A. clauda Dur. Disarticulation occurs at the lower floret only . . . . . . . . . . . . . A. pilosa M.B. 5. Disarticulate each floret at maturity or panicle non-shattering Florets disarticulating at maturity, plant with juvenile growth prostrate 6. Glumes 40 mm long, callus very long, awl shaped, 10 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. longiglumis Dur. Glumes 10–20 mm long, callus round or absent 7. Low floret disartuculates only, callus elliptic, awn inserted at 1/3 of lemma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. atlantica Baum Disarticulate each floret at maturity 8. 2 3 14 4 5 6 7 Panical non-shattering 15. Disarticulate each floret at maturity Disarticulation occurs at the lower floret only 16. Spikelets with 2–3 florets, glumes 20–25 mm long . . . . . . . . . A. fatua L. Spikelets with 3–4 florets, glumes 15–20 mm long . . A. occidentalis Dur. 17. Callus very long, awl shaped Callus elliptic, oval or round shaped 18. Callus 5 mm long, glumes 27–30 mm long . . . . . . . . A. ventricosa Balan. Callus 10 mm long, glumes about 40 mm long . . . . . A. bruhnsiana Grun. 25 16 17 18 19 9 20. Spikelets small size with 2–3 florets, glumes 18–20 mm long . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. canariensis Baum et Fed. Spikelets small size with 2 florets, glumes 15–18 mm long . . . A. agadiriana Baum et Fedak. 21. Spikelets large size with 2 rarely 3 florets, glumes 25–30 mm long. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A. ludoviciana Dur. Spikelets large size with 3–5 florets 22 22. Callus round shaped 23 Callus elliptic or oval shaped 24 23. Spikelets with 3–4 florets, lemma highly pubescent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. magna Murphy et Terr. Spikelets V-shaped with 3–5 florets, lemma slightly-moderate pubescent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. sterilis L. 24. Awn inserted at about one-quarter of lemma, callus oval . . . A. murphyi Lad. Awn inserted at lower one-third to one-half of lemma, callus elliptic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. insularis Lad. 25. Fracture surface at the base of the primary floret is straighting . . . A. sativa L. Fracture surface at the base of the primary floret is slanting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. byzantina C. Koch. Panical non-shattering 13 Spikelets very small 12–15 mm . . . . . . . . . . . . . . . . . . . . . A. prostrata Lad. Spikelets 20 mm long . . . . . . . . . . . . . . . . . . . . . A. damascena Raj. et Baum 10. Lemma tips biaristulate, glumes with 9–10 veins . . . . . . . . . A. barbata Pott. Lemma tips biaristulate with 1–2 denticula or without, glumes with 7–9 veins 11 9. 11. Lemma tips biaristulate with 1 denticulum, lemma tips longer than glumes; first floret scar narrow elliptic . . . . . . . . . . . . . . . . . . . . . . A. hirtula Lag. Lemma tips biaristulate with 2 denticula, lemma and glumes equal or nearly 12 so; first floret scar oval 12. Lemma tips biaristulate 3–6 mm long . . . . . . . . . . . . . . . . . .A. wiestii Steud. 20 21 I.G. Loskutov and H.W. Rines 19. Spikelets small size, glumes 15–20 mm long Spikelets large size, glumes 25–30 mm long 10 13. Lemma tips biaristulate with 1 denticulum, lemma and glumes nearly equal, panicle equilateral or unilateral . . . . . . . . . . . . . . . . . .A. strigosa Schreb. Lemma tips biaristulate with 2 denticula, lemma tips shorter than glumes, panicle unilateral. . . . . . . . . . . . . . . . . . . . . . . . . . .A. abyssinica Hochst. 15 8 Disarticulate each floret at maturity Lemma tips biaristulate 1 mm long. . . . . . . . . . . . . . . A. vaviloviana Mordv. 14. Florets disarticulating at maturity 3 Avena Table 3.9 Speciation in the genus Avena L. (Loskutov 2007) Section Species Wild Floret disarticulation Spikelet disarticulation Aristulatae (Malz.) A. clauda Dur. A. pilosa M. B. Losk. A. prostrata Ladiz. A. damascena Raj. et Baum A. longiglumis Dur. A. wiestii Steud. A. atlantica Baum A. hirtula Lagas. A. barbata Pott. A. vaviloviana Mordv. Avenae Losk. A. ventricosa Bal. A. bruhnsiana Grun. A. canariensis Baum A. agadiriana Baum et Fed. A. magna Mur. et Terr. A. murphyi Ladiz. A. insularis Ladiz. A. fatua L. A. sterilis L. A. occidentalis Dur. A. ludoviciana Dur. species, the same number of bands being typical of the monomorphic tetraploid endemic oat A. vaviloviana (AB). The largest number of bands (over 20) is characteristic of the As-genome species and the tetraploid oat A. barbata (AB) only. All hexaploids (ACD) contained 18–19 bands. The number of electrophoretic banding patterns may be connected with the degree of distribution and adaptiveness of the given wild species in nature. The species with the minimum number of bands have a very limited natural habitat, while the species with the largest number of bands and types of electrophoretic banding patterns have quite a wide distribution, such as, for instance, the diploids A. hirtula and A. wiestii, the tetraploid A. barbata, hexaploid species A. ludoviciana and A. sterilis, and of course A. fatua that weeds crop fields in the cereal belt around the globe. In general, the data analysis has shown that the level of polymorphism in terms of types of electrophoretic banding patterns was the highest in hexaploid species and the lowest in tetraploid and diploid species (Loskutov 2007). Among, other markers, a sufficient polymorphism was discovered by an analysis of isoenzyme systems. Definite isoenzyme loci were characteristic of different populations of A. barbata depending on the air temperature, soil type and place of growth (Allard 1997; Perez de la Vega 1997; Guma et al. 2006). AU16 2n Genome 14 Cp Ap Ad Al As 28 AB 14 Cv 28 Ac AB? AC Cultivated A. strigosa Schreb. A. abyssinica Hochst. A. byzantina Koch A. sativa L. 42 AC? ACD Although Spanish and Californian A. barbata gene pools are closely similar in allelic composition and allelic frequencies, large differences are in multilocus genetic structure. Isoenzyme analysis involving 15 loci revealed 33 alleles and 38 genotypes common in Spanish and Californian populations, 20 alleles and 45 genotypes were found only in Spain, and 2 alleles and 3 genotypes only in California. These results describe an increasing variability and less fixed genotypes when comparing populations from California vs. Spain or Spain vs. Israel and southwestern Asia, the former gene pools being more similar to each other than to the eastern Mediterranean ones, which suggests founder effects, genetic drift, and selection during the westward distribution. A. barbata was introduced to California by ship from Southern Spain (Garcia et al. 1989). Many researchers have obtained results concerning wide intraspecific isoenzyme diversity within wild species (Craig et al. 1974; Hoffman 1996). The largest differences in the isoenzyme composition of oat proteins were found to exist at the interspecific level, and the differences were stronger in species with different genomes (Craig et al. 1972; Sanchez de la Hoz and Forminaya 1989). Significant differences by these traits were discovered for A. barbata and A. fatua among the populations initially growing in the eastern I.G. Loskutov and H.W. Rines hemisphere and carried to the western one (Marshall and Allard 1970; Kahler et al. 1980). The widest diversity of the isoenzyme composition in the studied oat accessions has been found within forms of the diploid species A. canariensis from Fuerteventura Island (the Canaries), if compared with populations from Lanzarote Island in the same archipelago (Spain). It should be noted that the isoenzyme composition data correlated very well with the data on plant morphological traits. The differences in isoenzyme composition among populations of the same species were stronger than between individual species and between populations found on different continents (Morikawa and Leggett 1990; Morikawa 1991, 1992). A similar result was obtained from a study of the tetraploid species A. agadiriana (Morikawa and Leggett 2005). A study of the diversity of mitochondrial DNA enzymes has shown that forms of A. fatua and A. sterilis were similar or identical to those of oat cultivars (Rines et al. 1983, 1988). A study of isoenzyme composition in a representative set of A. sterilis accessions of different geographic origin has recorded a large diversity both for separate groups of populations and within each group. The largest diversity has been registered within A. sterilis populations collected in different regions of Turkey (Phillips et al. 1993). Further studies of this trait in bred oat cultivars from USA and Canada and in wild species have shown wild populations to have a wider diversity compared to cultivars (Murphy and Phillips 1993). A study of isoenzyme composition and morphological traits of A. sterilis populations of different geographic origin has determined that the average coefficients of affinity between the accessions studied using various methods were very small. Therefore, the data on isoenzyme composition cannot be completely used for checking morphological purity of collection accessions and their genetic integrity after regeneration (Beer et al. 1993). The DNA marker methods, the development of which has been recently going quite actively, are promising for investigating polymorphism in oats. Molecular marking of genetic systems in an organism is based on the use of biological specificity of nucleic acids. Restriction fragment length polymorphism (RFLP) markers applied for mapping genome and its loci using electrophoretic patterns has become widespread among the genetic marker techniques employing this feature. Moreover, randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), highly variable microsatellites markers, polymorphism of ribosomal DNA, etc. are commonly applied in botanical, genetical, and breeding research. The RFLP, RAPD, and other marker techniques are used for studying polymorphism in diverse materials for different purposes, for instance, for genetic mapping and determining genetic affinity between oat species at the DNA level (O’Donoughue et al. 1992; Van Deynze et al. 1995), for identifying alleles of the genes controlling characters of importance for breeding (Howarth et al. 2000), or for clarifying intraspecific variation (Hayasaki et al. 2001). The application of DNA markers gives valid and reliable results only when it is complemented by a complex study of a thoroughly selected specific diversity (Heum et al. 1994; Jellen et al. 1994; Katsiotis et al. 1996, 1997; Abbo et al. 2001). The study of a representative set of wild A. sterilis populations collected on both Asian and African continents was carried out by RFLP markers. The highest genetic polymorphism was observed for the accessions collected in Iran and the lowest one for Ethiopian accessions. Cluster analysis performed using the test results has clearly split all populations into two groups according to the geographic principle, that is, from the eastern (Iran and Iraq) and western (all other countries) regions. Besides, the second group was subdivided into two subgroups, one including populations of Southwest Asian origin (from Israel, Lebanon and Syria) and the other one of African origin (from Algeria, Morocco, and Ethiopia) (Goffreda et al. 1992). The questions of phylogeny and systematic position of species are actively disputed at present time. In this relation, the search for new approaches to solving the problems of genome affinity and systematic position of Avena species in genus is quite relevant. DNA markers are promising tools to be used when carrying out investigations in this direction, and RAPD analysis is one of the possible research methods. For instance, a study based on RAPD analysis has demonstrated a possibility of distinguishing between representatives of 20 oat species according to their genomic composition, ploidy level, and intraspecific differentiation. Subsequent research has confirmed the findings (Drossou et al. 2004). Diploid species were found to display a wider range of polymorphism in 3 Avena comparison with the polyploid oat species. It has been established that all the As-genome species differed from those with the A genome types (A. atlantica, A. longiglumis и A. canariensis). Regardless of all distinctions between these species, the data may suggest their indirect evolutionary closeness, and this confirms the conclusions made by other researchers on the basis of molecular markers application (Morikawa 1992). It should be noted that all representatives of diploid species with the C-genome types had a low level of similarity with the A-genome species, as well as within their group between the Cv and Cp genomes, thereby confirming the remoteness of both individual genomes (A and C) and even different genome types (Cv and Cp) from each other. The differences between A. pilosa and A. clauda, with the same structure of the Cp genome, were also significant, thus confirming their remoteness and correctness for classifying them as two separate species. Substantial differences were characteristic of two groups of tetraploid species with the AB (A. barbata and A. vaviloviana) and AC genomes (A. magna and A. murphyi). The degree of difference between all the species in these groups was significant and confirmed correctness of systematic individualization of each of them (Loskutov 2007). Another molecular marker technique, AFLP, was applied to screen 163 accessions of 25 Avena species with diverse geographic origins. For each accession, 413 AFLP polymorphic bands detected by five AFLP primer pairs were scored. All the species were clustered together according to their ploidy levels. The C genome diploids appeared to be the most distinct, followed by the Ac genome diploid A. canariensis. The Ac genome seemed to be the oldest in all the A genomes, followed by the As, Al, and Ad genomes. The AC genome tetraploids were more related to the ACD genome hexaploids than the AB genome tetraploids. Analysis of AFLP similarity suggested that the AC genome tetraploid A. maroccana was likely derived from the Cp genome diploid A. eriantha and the As genome diploid A. wiestii and might be the progenitor of the ACD genome hexaploids. These AFLP patterns are significant for our understanding of the evolutionary pathways of Avena species and genomes, for establishing reference sets of exotic oat germplasm and for exploring new exotic sources of genes for oat improvement (Fu and Williams 2008). The technique of microsatellites markers has many desirable marker properties. According to Li et al. (2000), using microsatellite polymorphisms, dendrograms were constructed showing not so completely clear phylogenetic relationships among Avena species. On the other hand, according to Fu et al. (2007), the study attempted to characterize a structured sample of 369 accessions representing 26 countries and two specific groups with Puccinia coronata avenae (Pc) and Puccinia graminis avenae (Pg) resistance genes using microsatellite (SSR) markers. Analyses of the SSR data showed the effectiveness of the stratified sampling applied in capturing countrywise SSR variation. Accessions from Greece, Liberia, and Italy were genetically most diverse, while accessions from Egypt, Georgia, Ethiopia, Gibraltar, and Kenya were most distinct. Accessions with Pc and Pg genes had similar levels of SSR variation, did not appear to cluster together, and were not associated with the other representative accessions. They conclude that these SSR patterns are significant for understanding the progenitor species of cultivated oat, managing A. sterilis germplasm, and exploring new sources of genes for oat improvement. Consensus chloroplast simple sequence repeat (ccSSR) makers were used to assess the genetic variation and genetic relationships of Avena species. The analysis of genetic similarity showed that diploid species with the A haplome were more diverse than other species, and that the species with the As haplome were more divergent than other diploid species with the A haplome. Among the species with the C haplome, A. clauda was more diverse than A. eriantha and A. ventricosa. As for the maternal donors of polyploid species based on this maternally inherited marker, A. strigosa served as the maternal donor of some polyploid species such as A. sativa, A. sterilis, and A. occidentalis from Morocco. A. fatua is genetically distinct from other hexaploid species, and A. damascena might be the A genome donor of A. fatua. A. lusitanica served as the maternal parents during the polyploid formation of the AACC tetraploids and some AACCDD hexaploids (Li et al. 2009). Later, the technique of ITS1 and ITS2 sequences was found to be effective for taxonomic and evolutionary pathway research. To examine the genomic constitution of A. macrostachya, the individual genes from three oat species with AsAs karyotype (A. wiestii, A. hirtula, and A. atlantica) and those from A. longiglumis (AlAl), A. canariensis (AcAc), A. ventricosa (CvCv), I.G. Loskutov and H.W. Rines A. pilosa, and A. clauda (CpCp) were sequenced. All species of the genus Avena examined represented a monophyletic group, within which two branches, i.e., species with A- and C-genomes, were distinguished. A. macrostachya, albeit belonging to the phylogenetic branch of the C-genome species, has preserved an isobrachyal karyotype, probably typical of the common Avena ancestor. It was suggested to classify the A. macrostachya genome as a specific form of C-genome (Rodionov et al. 2005). C-genome clones were sequenced and the analysis revealed close proximity to A. ventricosa ITS1-5.8SITS2 sequences, providing strong evidence of the latter’s active role in the evolution of tetraploid and hexaploid oats. In addition, cloning and sequencing of the chloroplast trnL intron among the most representative Avena species verified the maternal origin of A-genome for the AACC interspecific hybrid formation, which was the genetic bridge for the establishment of cultivated hexaploid oats (Nikoloudakis and Katsiotis 2008). Major genic divergence between the A and C genomes was revealed, while distinction among the A and B/D genomes was not possible. High affinity among the AB genome tetraploids and the As genome diploid A. lusitanica was found, while the AC genome tetraploids and ACD hexaploids were highly affiliated with the Al genome diploid A. longiglumis (Nikoloudakis et al. 2008). The species and their genome relationships among 13 diploid (A and C genomes), six tetraploid (AB and AC genomes), and five hexaploid (ACD genome) to infer evolutionary pathways in Avena were investigated by using the plastid matK gene and the trnL-F region and the nuclear ribosomal internal transcribed spacers (ITS). The evaluation is presented that the B and D genomes of Avena could be regarded as variants of the A genome. Avena wiestii (AsAs) likely was the maternal parent of most AACCDD species, AACC tetraploids, and A. agadiriana (AABB). Avena hirtula (AsAs) was the maternal parent of the other three AABB tetraploids, and A. damascena (Ad Ad) is the maternal parent of A. fatua. A high degree of homogenization in the ITS sequences was found, except in A. fatua, which had two types in separate clades, one with A genome and one with C genome carrying species. The C genome was always differentiated from the undifferentiated A, B, and D genomes groups in each gene tree as well as in the tree obtained from the three genes combined (Peng et al. 2009). The analysis of data has demonstrated that the different research methods involving molecular markers should not be regarded as universal tools in oat studies; however, their correct application combined with the use of other approaches can yield the desired results. The undoubtful advantage provided by such markers is in the possibility to study plant genetic diversity right at the level of DNA, the carrier of hereditary information. That is why these markers have recently got a wide application for genetic mapping, analyzing plant polymorphism, phylogeny, and taxonomy. 3.4 Role in Classical and Molecular Genetic Studies The most promising method of reducing genetic erosion within the cultivated species is in using wild species along with cultivated ones in breeding activities. Practical significance of the breeding work is in successful transfer of valuable traits from wild species to cultivated forms. In terms of crossability, all Avena species are grouped into three gene pools based on the gene pool classification system proposed by Harlan and de Wet (1971). The primary gene pool includes all cultivated and hexaploids wild species, which directly cross with cultivated oat easily. The secondary gene pool contains some tetraploid species (A. magna, A. murphyi, A. insularis, etc.), which cross with cultivated oat directly, though they produce sterile progeny. Hybrids of A. sativa with these species are partially, and increasing with backcrossing, female fertile, and natural recombination occurs best with A. insularis. The secondary gene pool contains several desirable traits and needs to be better explored in respect to collection as well as evaluation. The tertiary gene pool includes diploid and the remaining tetraploid species requiring application of in vitro techniques for hybridization (Jellen and Leggett 2006). Nevertheless, it is considered a rich reservoir of diversity for oat breeding. In their turn, the crosses between cultivated and wild oats can be subdivided into two groups (1) the ones that proceed easily and gave either fertile (with 3 Avena all hexaploid species) or partially sterile (with AC genome species A. magna and A. murphyi) progeny, and (2) the crosses that proceed with difficulty and gave a progeny that is either sterile to a considerable degree (e.g., with A. barbata) or completely sterile, as is the case with A. prostrata and A. vaviloviana (Leggett 1996). The difficulty of transferring alleles from diploid and tetraploid species into hexaploid forms had been noticed by many authors (Leggett 1996; Mitrofanov and Mitrofanova 1972), and its essence is in crossing the crossability barrier. This problem can be solved by using mutants, genetic transformation, or by applying the method of backcrosses. Chromosome duplication induced by colchicine treatment is often used to overcome sterility of the hybrids between diploid species and the hexaploid cultivated oats. Irradiation with thermal neutrons made it possible to cross the tetraploid species A. abyssinica with A. sativa (Sharma and Forsberg 1977). The possibility of transferring entire chromosomes or their parts from diploid species to the cultivated hexaploid oat genome using genetic carriers has been confirmed by successful hybridization of many species. The most promising among the method for overcoming the inability of chromosomes to conjugate employs the CW-57 accession of diploid A. longiglumis, which facilitated the homeologous chromosome conjugation at the transfer of traits from tetraploid A. barbata to hexaploid A. sativa (Thomas 1988). The reason is that the diploid species contains the “wild” diploidization suppressor allele and the gene responsible for the genome recombination (Rajhathy 1966). A good example of using such a vector is the creation of the hexaploids Amagalon line by crossing A. sativa with A. magna via A. longiglumis. The same procedure may be used for crossing other species, too. Fertility of the pentaploid sterile hybrids, which can be obtained through simple crosses between tetraploid A. magna, A. murphyi, and hexaploid A. sativa, can later be completely restored through backcrossing these hybrids with the cultivated oat. This scheme of using tetraploid species in breeding oat for grain quality and large grain size was developed in Sweden (Hagberg 1983). The procedure of natural backcrossing by growing pentaploid F1 hybrids on the plots of cultivated oat can also be applied when A. barbata and A. macrostaсhya are used in crossings. For the first time, wild hexaploid oat species were experimentally used in breeding for an increased grain yield in 1936. The species A. fatua had been recommended for the purpose. It was proved that the main traits of cultivated oat dominated in the progeny from interspecific hybrids (Emme 1938; Vavilov 1962). A study of interspecific hybrids did not confirm the opinion that the hybrid resulting from a cross with hexaploid A. sterilis is difficult to get rid of a set of such “wild” traits as the presence of callus increased huskness of grains, wild type of awnedness, etc. (Popovic 1960). The use of the species in cultivated oat breeding has been found to significantly increase biomass and vigor in hybrid plants. These traits were discovered to be controlled by additive alleles. For the first time, wild oat species were used for practical breeding purposes in the 20s of the twentieth century. However, the earliest commercial varieties created with their use appeared only in the 1960s. In the former USSR, A. fatua had been used by breeders in their work for development of winter type of oat varieties (Loskutov 2007). In Great Britain, diploid and tetraploid wild oat species have been successfully used as sources of resistance to the most important oat disease, which is mildew. The trait of resistance had been transferred from A. barbata into a series of oat cultivars, namely Maris Tabard, Maris Oberon, Margam, and Maldwyn (Jones et al. 1984). A. fatua had been used for creating the winter oat Mostyn that carries genes for mildew resistance (Hayes 1970). Beginning in the 1960s, oat breeding in the US has widely employed the use of wild hexaploids species (Frey 1991, 1994), particularly for disease resistance. The species A. fatua and A. sterilis have served as major contributors in creating many oat cultivars, which have occupied or now occupy considerable areas in the US, Canada, Brazil, and Australia. Therefore, the availability of well-developed breeding methods and numerous successful practical results confirm the possibility of effective transfer of many agronomically important traits into cultivated oat by means of interspecific hybridization for raising hereditary potential and broadening genetic basis of the entire genus. Genetically, oat is insufficiently studied in comparison with other cereal crops. The trait-oriented genetic collections composed in different laboratories AU17 I.G. Loskutov and H.W. Rines in Europe and America are small (Dielz 1928; Litzenberger 1949; Fleischmann et al. 1971b; Simons et al. 1978; Marshall and Shaner 1992; Nielsen 1993), though the first genetic research on the inheritance of morphological traits in oats, e.g., color and pubescence of glumes (Surface 1916), has been carried out since the beginning of the twentieth century. Significant attention in genetic studies have been paid to morphological traits of generative organs, which were studied most thoroughly in relation to the problems with systematics and phylogeny of the genus Avena. Later on, the genes governing resistance and susceptibility to diseases and pests have been identified and genetic control of polymorphic protein systems and generative organs development has been established, thus making these data very useful for breeding purposes. In 1978, a list of genes was published (Simons et al. 1978) and extended in 1992 (Marshall and Shaner 1992). Over 300 genes controlling different traits have been identified in oats, and only single alleles responsible for morphological traits were localized in concrete chromosomes. Later on, composition of the genetic collection kept growing continuously, mainly following new publications, primarily in “Crop Science” and “Oat Newsletter.” In 1997, VIR published a Catalog with descriptions of accessions in the genetic oat collection (Loskutov 2007), which included cultivars, cultivated lines, and wild accessions with one or more identified genes controlling different morphological, agrobiological, biochemical, and other traits. A big part of the collection is represented by accessions with the most important genes of resistance to mildew, crown and stem rusts, and smut species. At present, the genetic collection of oats at VIR includes over 600 accessions belonging to both cultivated (A. sativa, A. byzantina, A. strigosa, A. abyssinica) and wild (A. sterilis, A. barbata, A. magna) species that contain over 200 identified genes controlling different morphological, physiological, biochemical, and other traits. The use of donors with the identified genes that ensure clear manifestation of a trait makes it possible to predict the results of investigations with sufficient precision, it being quite important when carrying out breeding for quality, plant height, and other traits. The role of donors is especially important in broadening the genetic basis of cultivated oats concerning resistance to smut and rust species as well as other diseases. The use of the genetic collection increases efficiency of the breeding work, facilitates selection of parental pairs for crosses, and accelerates creation of cultivars with required parameters. All information about the accessions with identified genes from the oat genetic collection is available in the European Avena Database (EADB) established on the initiative of ECPGR and Avena Working Group at FAL (now part of the Julius K€uhn-Institute, JKI, Germany) (http://eadb.bafz.de/CCDB_PHP/eadb/). 3.5 Role in Crop Improvement Through Traditional and Advanced Tools 3.5.1 Potential of Wild Oat Germplasm for Oat Improvement The main objectives of agricultural crop breeding are to increase their productivity and improve grain quality characters. Raising plant productivity requires breeding cultivars with high productivity and quality potential as well as resistance to biotic and abiotic stresses. Resistance of wild oat species to unfavorable environmental factors, pathogenic organisms, their wide adaptability to different soil and climatic conditions, and a number of traits determining high productivity and quality are of special interest in the context of oat breeding. 3.5.1.1 Vegetative Period Oat displays great interspecific diversity in terms of duration of vegetative period. In oat breeding, duration of vegetative period is a very important character, which is directly related to grain yield, its quality, and seed sowing properties. Wild forms may contain populations with very different duration of the vegetative period (Trofimovskaya et al. 1976). In terms of duration of vegetative period, Malzev (1930) subdivides all oat species into spring, intermediate, and winter forms. The spring forms produce fertile stems within one summer; the intermediate forms produce turf similar to the winter ones and generate shoots during the first year of vegetation, while the winter forms do not produce fertile stems during this period. The late or winter phenotype is 3 Avena more characteristic of the diploid and tetraploid species. For A. sterilis, all three vegetative period phenotypes – from the winter to spring ones – are characteristic, while for A. ludoviciana, the winter one is more typical, and for A. fatua, the spring, early type of development is more characteristic. The northern forms of this species have been found to have a shortened vegetative period, while it is longer for the southern ones. The wild species are traditionally believed to have an extended vegetative period and its individual stages, but the performed investigations have yielded a wide range of early forms, the use of which in breeding for earliness may be quite promising. Some accessions of such species as A. canariensis, A. abyssinica, A. fatua, and A. sterilis have a shorter vegetative period, if compared to the cultivated forms, and can be both potentially and practically used in breeding programs (Trofimovskaya et al. 1976; Mal 1987; Frey 1991). A study of the BC2 breeding lines involving A. fatua has found them to burst out 3 days earlier than the parental forms (Stevens and Brinkman 1986). Another hexaploids species, A. sterilis, is believed by many authors to be an inexhaustible source of alleles determining a wide range of seed maturation dates (Welsh 1945; Hayes 1970; Hagberg 1983). Notable is that special earliness was characteristic of accessions of the species collected in Ethiopia (Rezai 1978). A big set of accessions of wild species has been analyzed from the point of view of the duration of vegetative period, and a considerable degree of variation in duration of separate stages of development was revealed by forms of A. clauda, A. pilosa, A. longiglumis, A. wiestii, A. hirtula, A. barbata, A. agadiriana, A. ludoviciana, and A. sterilis. Thus, early spring forms as well as late intermediate and semiwinter forms of oat have been found among these species (Loskutov 2007). The study has shown that the shortest individual stages of development and the entire vegetative period among diploid and tetraploid species were characteristic of A. prostrata, A. canariensis, A. atlantica, A. vaviloviana, and A. magna, while the longest – of A. bruhnsiana, A. ventricosa, and A. agadiriana. It should be noted that the difference between the lowest and highest average values amounted to over 20 days. Among hexaploid species, A. fatua showed the shortest individual stages of development and the entire vegetative period, while A. sterilis, A. ludoviciana, and A. occidentalis had the longest ones. The average value difference between these species was only 10 days (Loskutov 1998, 2007). Therefore, the analysis of correlations between duration of different phases and the entire vegetative period shows a higher probability of discovering more early or spring forms in the northwest of the Mediterranean center of origin of cultivated plants, that is, in southwestern Europe and northwestern Africa and its archipelago, while intermediate spring and semi-winter forms are more likely to be found in the west of the Asian continent. Besides, the localities where the endemic Ethiopian species A. vaviloviana had been collected suppose the origin of the most early forms presumably from the regions located southeast of Addis Ababa and from the southern coastal regions of Ethiopia (Loskutov 2007). To sum it up, investigations of the cultivated forms of oat have been accompanied by the analysis of data from studies of wild oat species with different ploidy levels, which has shown the presence of early spring forms possessing either individual shortened stages of plant development or a shorter vegetative period. These forms can be used in breeding early cultivars. 3.5.1.2 Response to Photoperiod and Vernalization The most important factors determining a plant’s vegetative period duration, especially before heading, are the day-length and temperature regime. Not only winter crops need vernalization at the early stage of development but also almost all oat species require it to a small degree. The influence of day-length and low temperatures on the initial stages of oat species development had been noted by many researchers (Qualset and Peterson 1978; Thomas and Naqvi 1991; Rodionova et al. 1994). A study of A. byzantina has singled out a unique, photoperiod-insensitive Turkish oat landrace, which was later on quite widely used worldwide in breeding oat for photoperiodic sensitivity (Sampson and Burrows 1972). Besides, weak response to photoperiod has been described for some A. abyssinica accessions (Razumov 1961; Arias and Frey 1973; Loskutov 2001a). Some forms of wild species have been shown to be insensitive to photoperiod and vernalization. The reason is that the center origin and diversity of wild I.G. Loskutov and H.W. Rines oat species are located in the Mediterranean region, countries on the Black and Caspian seas, and in Central Asian countries. The widest diversity is found between 30 and 40 N (Vavilov 1965a, 1992; Baum 1977). Initial stages of development of many wild oat species fall on cold months; besides, they grow at high altitudes (up to 2,000 m), hence are peculiarities of their response to the environmental factors including photoperiod and temperature (Paterson et al. 1976; Darmency and Aujas 1986). Screening of a large set of wild species has identified truly winter genotypes within A. clauda, A. barbata, A. ludoviciana, and A. sterilis, and truly spring forms within A. wiestii, A. canariensis, and A. magna. A. vaviloviana and A. fatua may be regarded as truly spring species because of their neutral or weak response to vernalization. Besides, forms of A. fatua have displayed a strong response to day-length (Loskutov 2007). The typically spring type of development of these species indicates their secondary origin compared to those characterized by winter and semi-winter forms, it being confirmed in literature (Jellen and Beard 2000). Apparently, the availability of spring forms and a strong day-length sensitivity allow the forms of A. fatua to spread to the northernmost territories and climb up high into the mountains to the altitudinal limits of high mountain agriculture (Loskutov 2007). Forms of A. hirtula, A. vaviloviana, and A. occidentalis displayed weak response to photoperiod, while forms of A. clauda, A. murphyi, and A. sterilis showed a very strong response to day-length variation (Loskutov 2001a). A perennial autotetraploid species A. macrostachya displayed a strong photoperiodic response under vernalization, while forms of A. magna were strong day-length sensitive (Sampson and Burrows 1972; Loskutov 2007). Response to vernalization has been shown to depend on geographic origin of particular accessions, while response to photoperiod variation has been found to be predominantly species-dependent. There exists no direct relation between geographic origin of a species and photoperiodic response. At the same time, several accessions with a very weak or neutral photoperiodic sensitivity originated from the regions either adjacent to, or located south of 40 N, that is, from the Canaries (Spain), Corsica (France), Crete (Greece), Azerbaijan, Turkey, Morocco, Tunisia, Lebanon, and Ethiopia (Loskutov 2001a, 2007). 3.5.1.3 Plant Height and Lodging Resistance Variation in plant height is quite high among species of the Avena genus. This helps to select and create new initial material combining optimal plant height with other agronomically important traits. Wild oat species with different ploidy levels have been studied with the aim of broadening the genetic basis of such traits as semi-dwarfness and lodging resistance. The use of a fairly short-stem diploid species A. pilosa in stepwise hybridization has been found to reduce plant height in cultivated oat (Hoppe and Hoppe 1991). According to many authors, hexaploid species A. fatua and A. sterilis are the sources of new alleles of genes determining wide variation in plant height (Welsh 1945; Hayes 1970; Frey 1991). A study has shown that among diploid and tetraploid species, the lowest plant height was characteristic of endemic species from Spain (A. prostrata), the Canaries (A. canariensis), and from Morocco (A. agadiriana). Some semi-dwarfness forms of other species have been found in Azerbaijan (A. pilosa), Cyprus (A. ventricosa), Iran (A. clauda), Syria (A. pilosa), Morocco (A. damascena, A. magna), and Algeria (A. hirtula). Plants of A. fatua and A. ludoviciana with an average height of up to 65 cm have been found in Turkey, Iran, Iraq, Israel, Morocco, Ethiopia, and Kenya. The overwhelming majority of semi-dwarf accessions belong to A. sterilis. Itsgrows to an average height of up to 50 cm and it originated from Turkey, Iran, Iraq, Syria, Israel, Morocco, Tunisia, and Lebanon (Loskutov 2007). The problem of plant height is closely related to oat lodging; it occupies a special place in oat breeding and attracts significant attention because of the plant habit peculiarities. Due to morphological characters, (juvenile growth prostrate to semi-prostrate, flowering thin stems geniculate and high “windage” of the panicle), the majority of wild species are sensitive to lodging. However, some forms of the hexaploid A. occidentalis have been found to have an erect juvenile growth and thicker stem walls, the structure of which resembled that of A. magna. These characters may be used for improving lodging resistance in cultivated oat (Baum 1971). A study of a diploid species A. wiestii has shown that its forms possess a wide range of adaptive responses of the root system related to lodging resistance (Holden 1969). At the same time, a study of root volume and growth rate in A. sterilis has identified an 3 Avena accession from Sicily with quantitative characters (volume of the root system, root dry weight, panicles, and straw dry weight) 2–3 times higher than those in other forms of wild and cultivated oats (Carrigan and Frey 1980). Among the diversity of wild hexaploid species of plant height and lodging resistance, the most interesting semi-dwarf and lodging resistant forms have been found among A. fatua, A. ludoviciana, and A. sterilis (Loskutov 2007). To sum it up, selection of new sources of shorter plant height and lodging resistance among both cultivated and wild species allows the breeders to enjoy a higher degree of flexibility in their work and thus reduce the risk of genetic erosion of genotypes at the intraspecific level. 3.5.1.4 Agronomical Important Characters The main trend in breeding is the raising of a cultivar’s grain productivity. In the first place, this character and quality of oat cultivars depend on the panicle size, number of grains in the panicle, size, and presence/absence of husk on the caryopsis. A study of the elements of productivity in wild oat species has shown that the highest number of spikelets in the panicle and the highest density of the latter were characteristic of some forms of A. prostrata, A. wiestii, A. vaviloviana, A. abyssinica, A. fatua, and A. sterilis (Trofimovskaya et al. 1976; Thomas and Griffiths 1985; Mal 1987; Kanan and Jaradat 1996). High values of the same characters were demonstrated by accessions of A. hirtula and A. wiestii collected in Italy (Sicily and Sardinia), Azerbaijan, Iran, Israel, and Egypt, of A. barbata from Azerbaijan, Israel, and Lebanon, of A. vaviloviana collected in Ethiopia, and of A. fatua collected in Georgia, Kazakhstan, Bulgaria, and China (Loskutov 2007). Some accessions of A. sterilis from Central Asia and the Middle East were also noted for these characters (Rezai and Frey 1988, 1990). To a greater degree, a lower huskness correlates positively with grain size and high grain test weight and negatively with the degree of lodging and high susceptibility to rust diseases. Sources possessing these characters may be found among wild species, too. When crossed with cultivated oat, a diploid species A. pilosa with small grain and high percentage of huskness has reliably demonstrated an increase in the values of the characters (Hoppe and Hoppe 1991). The related tetraploid species A. magna, A. murphyi, and A. insularis have been noted for large grain size (1,000-grain weight reached 35 g) (Martens et al. 1980; Ladizinsky 1988, 1998; Loskutov 2007). A. sterilis is a rich source of alleles of genes governing variation of grain size in a wide range (Welsh 1945; Hayes 1970). The largest grain size and the highest 1,000-grain weight have been recorded for the accessions collected in Southwestern Europe and Northern Africa (Rezai and Frey 1989b, 1990). At the same time, some African forms of A. sterilis had impressive spikelets, which were 2.5-times larger than those of other species (Vavilov 1965a, 1992). Hybrid lines obtained by crossing A. fatua with cultivated oat had larger grain than the parental forms (Stevens and Brinkman 1986). The largest grain size has been found among the forms of A. fatua from Russia, Tajikistan, Poland, and Mongolia, of A. ludoviciana from Azerbaijan, Georgia, Turkey, and Iran, and of A. sterilis from Turkey, Iran, Iraq, Israel, Tunisia, and Morocco. The correlation analysis has shown the most large-grained forms of hexaploid species to be associated with southwestern Europe and northwestern Africa (Loskutov 1998). It should be noted that the most interesting forms with the weakest huskness and the largest 1,000-grain weight were the forms of A. fatua from Russia, Poland, and Mongolia, of A. ludoviciana from Azerbaijan and Iran, as well as of A. sterilis from Turkey and Tunisia (Loskutov 2007). Another character related to yielding ability is the productive tillering. A higher degree of productive tillering has been found to be characteristic of some forms of wild diploids A. prostrata, A. damascena, A. wiestii, and A. hirtula (Mal 1987; Kanan and Jaradat 1996) and tetraploids A. murphyi and A. magna (Ladizinsky 1988). When transferring this character from tetraploid species to a hexaploid cultivated species, two backcrosses are sufficient for obtaining stable hexaploid genotypes (Zadoo et al. 1988). The best forms of A. fatua are regarded by many authors as the best partners in breeding for higher yields and grain quality (Yamaguchi 1977). This species is promising for creating cultivars with different duration of seed dormancy, which permits to increase grain yields by 13–24% (Burrows 1970). The species transfers a higher spring sprouting ability and shattering resistance to cultivated oats (Frey 1985, 1991). I.G. Loskutov and H.W. Rines A consideration of yielding ability and other characteristics of interspecific hybrids involving A. sterilis shows that alleles of genes from wild species can increase vegetative vigor, grain yield, and straw weight in hybrid plants (Cox and Frey 1984a, b; Frey et al. 1984; Takeda and Frey 1985, 1987; Gupta et al. 1986a, b, 1987). To transfer these characters by means of interspecific crosses, the method of backcrosses is applied quite efficiently (Takeda et al. 1985; Frey 1988; Holland et al. 1996). Cytoplasm of a wild species had a significant influence on grain yield in certain combinations (Beavis and Frey 1987), total straw weight, plant height, and the vegetative vigor. The findings indicated the potential of A. sterilis for creating cultivars with a more stable productivity and less dependence on the environmental conditions (Robertson and Frey 1984). Thus, the study has found that wild species possess agronomically important characters, which may be used in improving the existing cultivars through breeding. 3.5.1.5 Resistance to Diseases and Pests Oat diseases and pests are still the main factors reducing yields and grain quality. The most efficient method of protecting plants from diseases and pests is the breeding of resistant cultivars. Their development requires different donors and sources of resistance. The main task of breeding for disease resistance is to restore in cultivated oats the lost genetic diversity as regards resistance to diseases and pests, initially possessed by wild progenitors. Therefore, a complex phytopathological study of all the specific diversity of Avena genus promotes identification of new sources and donors of resistance for their use for broadening genetic basis of the created oat cultivars (Clifford 1995). Resistance to Diseases Crown and stem rusts. Crown rust, caused by the fungus P. coronata Cda. f. sp. avenae Fraser et Led., and stem rust, caused by the fungus P. graminis Pers. f. sp. avenae Eriks. & Henn., are spread everywhere and affect the majority of oat crops. Numerous investigations of wild oat species show that their majority possesses a high degree of resistance to rusts (Table 3.10). For example, these are the diploid species A. clauda, A. pilosa, A. longiglumis, A. damascena, A. prostrata, A. canariensis, A. wiestii, and A. hirtula and tetraploids A. barbata, A. vaviloviana, A. abyssinica, and A. magna possessing complex resistance to rust species (Sebesta et al. 1987; Harder et al. 1992; Saidi 1998). According to Vavilov’s research (1935), the diploid species A. clauda and A. pilosa possessed resistance to crown rust (Vavilov 1951, 1964a). It had been established that the extreme variants of resistance to crown and stem rusts and to loose smut and powdery mildew are displayed by the diploid oat species (Vavilov 1951, 1964b, c). Consequent experiments with artificial infection of A. barbata have shown the existence of two very different groups, that is, a group strongly susceptible to all parasites and very resistant one. Forms of A. barbata from Persia, as well as forms of A. vaviloviana from Ethiopia, were strongly affected by rust species, while forms of A. sterilis happened to be susceptible to stem rust and medium resistant to crown rust (Vavilov 1965a, 1992). The performed analysis made it possible to suppose that high degree of resistance is displayed by representatives of the groups, which had formed under the conditions favorable for the development of infection, and that resistant forms should be sought in the areas where the parasite originated. It was further confirmed in his later works (Vavilov 1957). According to Mordvinkina (1969a), the Pyrenean and Moroccan groups of A. hirtula demonstrated complex resistance to fungous diseases, while the South Palestinian group and the forms from Corsica were susceptible to them. Medium resistance to crown rust was characteristic of the Mediterranean forms of A. barbata, though South-Asian forms got affected by this disease. In general, resistance of these species was confirmed in consequent studies (Simons et al. 1959; Leggett 1992a). The highest degree of resistance to crown and stem rusts was demonstrated by accessions of A. barbata collected in Israel (Dinoor and Wahl 1963). Forms of this species collected in Northern Australia were more resistant to stem rust than southern population (Burdon et al. 1983, 1992). Some forms of A. barbata possessed resistance only at the juvenile stage of development and were losing it during the reproductive stage (Karow et al. 1987). It had been established that crown rust resistance could 3 Avena Table 3.10 Sources of diseases resistance in oat species Species Genome Sources of resistance to powdery mildew Crown rust A. bruhnsiana Cv þ þ A. ventricosa Cv þ þ A. clauda Cp þ þ A. pilosa Cp þ þ A. prostrata Ap þ þ A. damascena Ad þ þ A. longiglumis Al þ þ A. canariensis Ac þ A. wiestii As þ þ A. hirtula As þ þ A. atlantica As þ A. strigiosa As þ þ A. barbata AB þ þ A. vaviloviana AB þ þ A. abyssinica AB þ þ A. agadiriana AB? þ A. magna AC þ A. murphyi AC þ þ A. insularis AC? þ A. macrostachya CC? þ þ A. fatua ACD þ þ A. occidentalis ACD þ þ A. ludoviciana ACD þ þ A. sterilis ACD þ þ be transferred to hexaploid species by means of amphiploid synthesis (Williams and Verma 1956). Reciprocal crosses have yielded a hexaploid line that contained an allele of the A. barbata gene governing resistance to stem rust Pg16 and had a grain yield nearly that of cultivated oat (Martens et al. 1983; Brown 1985; Ohm and Shaner 1992). When considering diversity of resistance to crown rust, it was found that resistance to this pathogen was displayed by forms of diploid species A. bruhnsiana, A. ventricosa, A. longiglumis, A. hirtula, of tetraploid species A. magna, A. insularis, A. murphyi, and A. macrostachya, while resistance to stem rust was found to be possessed by such diploids as A. pilosa, A. longiglumis, and A. hirtula and by a tetraploid A. macrostachya (Loskutov 2007). A. abyssinica may be of much importance for synthetic breeding in the case of stepwise interspecific hybridization involving 14 , 28 , and 42-chromosome oats aimed at transferring the well-expressed resistance to fungal diseases from the group of diploid oat species to cultivated oats (Vavilov 1965a, 1992). Stem rust BYDV þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ Smut ssp. þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ Septoria leaf blight þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ The species A. magna and A. murphyi have been found to possess a higher resistance to crown rust (Sebesta et al. 1987; Ladizinsky 1988; Leggett 1992a). High resistance to the most aggressive races of crown rust was displayed by sprouts and adult plants of A. magna (Murphy et al. 1968). This species and A. longiglumis as the carrier were used to produce the Amagalon (A. mag-na þ A. lon-giglumis) line, in which allele of the gene has been identified with molecular markers (Rooney et al. 1994; Wilson and McMullen 1996b). All investigations have found A. macrostachya, a perennial tetraploid species, to be characterized by resistance to both crown and stem rusts and that can be successfully crossed to cultivated oat (Leggett 1992b; Loskutov 2007). A study of the forms of A. fatua has found individual populations to have a higher degree of crown and stem rust resistance (Suneson 1948; Burdon et al. 1983; Simons and Briggle 1984; Johnson and Rothman 1986; Burdon and Muller 1987; Sebesta and Kuhn 1990). The accessions of A. fatua from Central Asia I.G. Loskutov and H.W. Rines displayed high resistance to 200 races of rust. The American populations of this species collected in the North Central states of the country happened to be susceptible to the stem rust isolates tested (Rines et al. 1980). On the whole, this species is characterized as having some resistance to stem and crown rusts (Frey 1991). According to many authors, the hexaploid species A. sterilis represents a rich source of alleles of genes controlling resistance to different races of crown and stem rusts (Welsh 1945; Suneson 1948; Hayes 1970; Harder et al. 1980, 1984; Frey 1983, 1991, 1994; Harder and McKenzie 1984; Wahl and Segal 1986; Leggett 1992a). It has been proved that in crosses involving the forms of A. sterilis, resistance of the progeny is influenced not only by the nuclear genetic material (Wilson and McMullen 1997a, b) but also by cytoplasm (Simons 1985; Simons et al. 1985). The inclusion of this species in the list of identifiers of physiological races of rust causal agents made it possible to identify almost 500 races of stem rust and 800 races of crown rust (Fleischmann and McKenzie 1968; Fleischman and Baker 1971; Fleischmann et al. 1971a, b). A study of several forms of this species has found correlations between crown rust resistance, protein content, potential grain yield, and powdery mildew resistance (Simons 1965, 1979; Popovic 1980). Alleles of rust resistance genes are frequently linked with the alleles controlling morphological traits of the grains, particularly color of lemma or its pubescence (Kiehn et al. 1976; Wong et al. 1983). Individual accessions of A. sterilis from southwestern Europe and countries of Asia and Africa are noted for a high resistance to rust diseases (McKenzie and Fleischmann 1964; McKenzie et al. 1970; Martens and McKenzie 1973; Kim 1974; Brodny et al. 1976; Rezai 1978; Simons 1985; Wahl and Segal 1986; Sebesta et al. 1987; Simons et al. 1987; Harder et al. 1990). The forms of A. sterilis from Turkey, Iran, and Iraq are resistant to crown rust and, apparently, possess an allele of the Pc54 gene or alleles of stem rust resistance genes (Martens et al. 1980, 1981). A. ludoviciana, related to A. sterilis, is also characterized by resistance to crown rust (Welsh 1945; Griffiths et al. 1959; Lupton and Thompson 1961; Clamot 1969; Hayes 1970; Sebesta et al. 1987) and to stem rust (Leggett 1992a). The accessions collected in northern Australia were more resistant to stem rust than southern forms of this species (Burdon et al. 1983; Oates et al. 1983). The accessions of A. sterilis, A. ludoviciana, and A. occidentalis with the highest resistance to crown rust originated from Spain, Italy, France, Turkey, Israel, Iran, Lebanon, Algeria, Tunis and USA. Complex resistance to the main obligate fungal parasites (crown and stem rusts) were characteristic of the forms of tetraploid species A. magna, A. insularis, and A. macrostachya and hexaploid species A. occidentalis, A. ludoviciana, and A. sterilis (Loskutov 1998, 2007). An analysis of the obtained data has shown that the forms of wild species with a higher resistance to crown rust were concentrated in the northwestern regions of the African continent, while resistant forms of A. barbata were concentrated in south of this species’ natural range where strong epiphytotics of crown rust are most frequent. Besides, it has been discovered that crown rust weakens the diseased plants and it leads to their medium infection by stem rust (Loskutov 2007). Powdery mildew is caused by the fungus Erysiphe graminis D. C. f. sp. avenae Em. March., is recorded everywhere and reveals itself on leaves, in leaf sheaths, and on plant stems (Table 3.10). According to Vavilov, accessions of the wild diploid species A. clauda and tetraploid A. barbata were characterized by a higher resistance to powdery mildew (Vavilov 1965a, 1992). Later on, Mordvinkina (1969b) determined geographic boundaries of these groups of A. barbata: powdery mildew resistance was characteristic of the Mediterranean forms, while South-Asian ones were susceptible to the pathogen. Further investigations undertaken by many authors have confirmed the supposition that these species possess resistance to powdery mildew (Aung et al. 1977; Aung and Thomas 1978; Thomas and Aung 1978; Harder et al. 1992; Leggett 1992a). According to many researchers, resistance to powdery mildew is exhibited by many wild species, namely diploid species A. pilosa, A. ventricosa, A. longiglumis, A. prostrata, A. damascena, A. hirtula, and A. atlantica; tetraploids A. barbata, A. vaviloviana, A. abyssinica, A. agadiriana, A. magna, and A. murphyi, and hexaploids A. fatua, A. occidentalis, A. sterilis and A. ludoviciana (Welsh 1945; Jones and Griffiths 1952; Lupton and Thompson 1961; Clamot 1969; Hayes 1970; Ladizinsky 1988, 1992; Thomas 1988; Frey 1991, 1994; Harder et al. 1992; Leggett 1992a; Zwatz et al. 1994; Herrmann and Roderick 1996). AU18 3 Avena The highest resistance was registered for all Azerbaijanian accessions of A. bruhnsiana, A. clauda, and some forms of A. pilosa, A. wiestii, and A. barbata (Loskutov 2007). A series of works on the transfer of alleles of the powdery mildew resistance genes from diploid species to cultivated oats have been undertaken at the Welsh Plant Breeding Station, University College of Wales (UK). The accession Cc 3678 (A. hirtula) was used to transfer powdery mildew resistance to hexaploid species via a genetic bridge of artificial amphiploids involving A. longiglumis (CW 57) (Thomas 1968). The accession Cc 4852 A. ventricosa, bearing an allele of the gene for resistance to powdery mildew races 2, 3, and 5, was included in the breeding program and crossing program (Thomas and Thomas 1970). The F4 line with a chromosome replacement from A. prostrata bearing a gene of powdery mildew resistance was obtained through production of an amphidiploid (A. longiglumis (CW 57)  A. sativa)  (A. sativa with chromosome A. prostrata) (Thomas and Griffiths 1985). A cross of A. macrostachya and A. prostrata has yielded a hybrid that was morphologically similar to A. macrostachya but was resistant to powdery mildew (Hoppe and Pohler 1988; Hoppe et al. 1990). Hexaploid species were not characterized by high resistance to the pathogen. At the same time, it should be noted that some resistant forms have been found among A. sterilis, A. ludoviciana, and A. occidentalis (Sebesta et al. 2000). Helminthosporium leaf blotch is caused by Drechslera avenae (Eidam.) Ito et Kuribay. (syn. Helminthosporium avenae Eidam; Pyrenophora avenae Ito et Kuribay.) and has been recorded everywhere (Sebesta et al. 2001). Resistance to this disease was noted in forms of diploid species A. bruhnsiana and A. wiestii from Azerbaijan, A. clauda from Turkey, A. longiglumis from Morocco and Algeria, and A. hirtula from Spain, Italy (Sardinia), and Tunisia. Among wild tetraploid species, high resistance was exhibited by A. macrostachya from Algeria. Resistance to Helminthosporium leaf blotch displayed by the AC-genome species A. magna and A. murphyi was above the average. Disease appearance was minimal also in other species, such as A. barbata from Turkmenistan, Portugal, Italy, Turkey, Israel, and Tunisia, A. magna from Morocco, and A. murphyi from Spain and Morocco. Among wild hexaploid species, there can be noted resistant forms of A. fatua from Russia, Ukraine, Azerbaijan, Turkey, and Iran, of A. ludoviciana from Azerbaijan, Georgia, and Iran, and of A. sterilis from Russia, Iran, Israel, Morocco, and USA. It should be noted that all accessions of A. occidentalis from Spain (the Canaries) had juvenile resistance and that their majority was resistant to the disease. An analysis of the gathered data has shown that the forms of wild species most resistant to Helminthosporium leaf blotch had been collected in the northern parts of natural ranges of wild oat species, which is near 40 N (Loskutov 2007). Septoria leaf blight is caused by the fungus Septoria avenae Frank. (syn. Leptosphaeria avenaria Weber.). It occurs everywhere and reveals itself from the tillering stage (Table 3.10). Among wild species, A. wiestii and A. sterilis apparently possess high resistance to Septoria leaf blight under both natural and artificial inoculation (Clark and Zillinsky 1960; Thomas 1988; Harder et al. 1992; Zwatz et al. 1994; Sebesta et al. 1999). Resistance to the disease was also characteristic of accessions of such diploid species as A. atlantica from Morocco, A. canariensis from Spain (the Canaries), A. damascena from Morocco, and A. hirtula from Italy (Sicily, Sardinia). Among wild tetraploid species, perennial A. macrostachya from Algeria has been noted for resistance to the disease in question. Moderate susceptibility has been recorded for A. vaviloviana and A. murphyi, and resistance has been displayed by forms of A. barbata from Azerbaijan, Portugal, and Israel. A sufficient number of forms with resistance to Septoria leaf blight have been found among hexaploid species. Many forms of A. fatua have been found to be resistant; they have geographically diverse origins: Russia, Ukraine, Georgia, Azerbaijan, Armenia, Kazakhstan, Tajikistan, Poland, Bulgaria, Czechoslovakia, Iraq, Turkey, Mongolia, and Argentina. The forms of A. ludoviciana from Czechia, Morocco, and USA have been found to be resistant to Septoria leaf blight. Among A. sterilis accessions, resistant forms originated from Turkey, Iran, Syria, Israel, Algeria, Morocco, Tunisia, Lebanon, and Ethiopia (Loskutov 2007). Myrothecium necrotic blight is caused by the fungus Myrothecium verrucaria Ditmar. ex Fran. and manifests itself in the beginning of vegetation, most often at the tillering stage or during the leaf-tube formation. Resistance to this pathogen has been displayed by accessions of diploid species from different AU19 I.G. Loskutov and H.W. Rines regions of Azerbaijan, such as A. bruhnsiana, A. pilosa, and A. wiestii, by forms of A. hirtula from Italy, Spain, Israel, and Tunisia, as well as by forms of tetraploid A. murphyi from Spain and Morocco, A. agadiriana from Morocco, A. barbata from Iran and Israel, and A. macrostachya from Algeria. The majority of hexaploid forms of A. fatua possessing resistance to Myrothecium necrotic blight originate from Russia, Armenia, Azerbaijan, Mongolia, and Ethiopia; those of A. ludoviciana have Russian, Ukrainian, Azerbaijanian, Georgian, Turkish, and Algerian origin and those of A. sterilis originate from Russia, Turkey, Iran, Syria, Israel, Algeria, Morocco, Tunisia, and US (Loskutov 2007). Smuts (caused by the fungi Ustilago avenae Jens. and Ustilago kolleri Wille.) occur everywhere and do much damage to oat crops. A study of complex resistance in oat species has shown that A. wiestii is not resistant to loose smut (Table 3.10). Experiments on artificial inoculation of A. strigosa and A. barbata with smut have identified two very contrasting groups within these species: that is, a group with strong susceptibility to all parasites, and another group with high resistance. The strongly susceptible forms of A. barbata happened to be typical of Persia. Among them, in some accessions, smut infection was localized to anthers only, while in most forms, it affected all organs of the inflorescence (Vavilov 1965a, 1992). According to Mordvinkina (1969a), moderate resistance to smut was characteristic of the Mediterranean forms of A. barbata, while the South-Asian forms were affected to a greater degree. According to Vavilov, the cultivated species A. abyssinica, its wild analog A. vaviloviana, and A. sterilis were quite susceptible to loose smut under conditions of Russia (Vavilov 1964c, 1965a, 1992). Further studies on resistance to loose and covered smut have shown that almost all previously studied species had forms that were resistant to this disease and could be used as donor sources in breeding for this character. The species A. strigosa, A. wiestii, A. barbata, A. vaviloviana, A. fatua, and A. sterilis (Forsberg and Shands 1989; Frey 1991; Harder et al. 1992; Leggett 1992a; Rodionova et al. 1994) as well as the majority of A. abyssinica accessions (Nielsen 1978, 1993) are regarded as resistant. A study of a large set of oat accessions has established that the majority of most resistant forms of A. sterilis originated from Ethiopia, Israel, Lebanon, Syria, and all North-African countries, but some of them were found in Iran and Iraq (Nielsen 1978). Fusarium is caused by fungi of the Fusarium genus. They are distributed everywhere and affect oats in the second half of the vegetation period. It is noted in numerous works that A. sterilis and A. ludoviciana represent a diverse source of resistance to Fusarium agents (Welsh 1945; Hayes 1970; Frey 1991; Gavrilova et al. 2008). Halo blight is caused by Pseudomonas coronofaciens Starr. and affects oat plants after the stage of tillering and leaf-tube formation. A. vaviloviana is resistant to halo blight and is of importance in breeding for increased productivity (Trofimovskaya et al. 1976). Barley yellow dwarf virus (BYDV) has recently become the most harmful disease of oat. It is caused by Hordeum virus nanescens Rademacer et Schwarz. When searching for new sources of resistance, a wide range of species has been studied and a number of BYDV-tolerant forms identified (Table 3.10). All these forms belong to the species A. longiglumis, A. strigosa, A. barbata, A. magna, A. murphyi, A. macrostachya, A. fatua, A. occidentalis, and A. sterilis (Frey 1983, 1991, 1994; Comeau 1988; Forsberg and Shands 1989; Harder et al. 1992; Leggett 1992a; Saidi 1998). A study of a representative set of accessions has found moderate tolerance in variants of the A-genome diploid species A. canariensis (Ac) and A. wiestii (As), while the most susceptible happened to be variants of the C-genome oat species A. bruhnsiana (Cv), A. ventricosa (Cv), A. clauda (Cp), and A. pilosa (Cp). Individual accessions had moderate tolerance, e.g., A. canariensis from Spain (the Canaries), A. clauda from Greece (Crete Island), A. damascena from Morocco, and A. hirtula from Algeria. Among the wild tetraploids, the overwhelming number of species displayed moderate tolerance to BYDV. The highest tolerance was exhibited by the forms of A. barbata from Azerbaijan and Israel, of A. vaviloviana from Ethiopia, of A. magna from Morocco, and of A. macrostachya from Algeria (Soldatov et al. 1990). The natural American populations of A. fatua collected predominantly in the Red River Valley in the Northeastern states of the US were found to have a higher BYDV tolerance (Rines et al. 1980). A. Comeau (1984) noted high tolerance in A. occidentalis and stressed the necessity of further collecting 3 Avena populations of this species, which are insufficiently represented in genebanks around the world, though these forms cross with cultivated oat easily. According to some authors, A. sterilis represents a source of alleles of genes governing resistance to different viral diseases, and therefore it should be used for breeding purposes to a greater degree (Welsh 1945; Hayes 1970). The majority of the most tolerant forms of this species were found in Greece, Algeria, Tunisia, Morocco, Lebanon, Ethiopia, Kenya, western Iran, and in the Mediterranean Turkey. Some tolerant accessions originated from Iraq, Libya, Israel, eastern Iran, and Anatolia (Turkey) (Comeau 1984; Landry et al. 1984). Accessions belonging to the group of hexaploid species were moderately tolerant to BYDV, depending on the species. The highest percentage (31%) of tolerant accessions was found within A. occidentalis, an endemic from the Canaries (Spain). The highest tolerance was characteristic of the A. fatua forms from Russia, Ukraine, Georgia, Tajikistan, Poland, and Mongolia, the forms of A. ludoviciana from Azerbaijan, Bulgaria, Afghanistan, Israel, Morocco, and of the A. sterilis forms from Turkey, Japan, Israel, and Morocco (Loskutov 2007). A comparison of the data on BYDV tolerance with those on the abundance of aphid population has identified the accessions with true resistance to BYDV, which belonged to the diploid species A. clauda, A. pilosa, A. canariensis, A. hirtula, and the tetraploid species A. barbata. Such forms have not been found within hexaploid species, as all of them got weakly populated with aphids. An analysis of the obtained data has shown that the forms of wild species with a higher BYDV tolerance had been collected from the regions located in the western parts of the natural ranges of wild oat species (Loskutov 2007). Resistance to Pests Pests cause serious damage, for instance, crop thinning, reduction of the productive tillers per plant, total or partial seed set failure, and lower grain and sowing material quality. Cereal cyst nematode and stem nematode (Heterodera avenae Woll. and Ditylenchus dispaci Filip., respectively) affect plants at different stages of their development and occur in many regions of oat cultivation. Cereal cyst nematode resistance has been found in the forms of the following wild species: A. canariensis, A. wiestii. A. strigosa, A. barbata, A. vaviloviana, A. abyssinica, A. magna, and A. murphyi (Harder et al. 1992; Leggett 1992a). In Australia, the forms possessing resistance to stem nematode have been selected from local populations of A. fatua (Scurrah et al. 1992). Other hexaploid species A. fatua, A. sterilis, and A. ludoviciana displayed resistance to different nematode species (Lupton and Thompson 1961; Hayes 1970; Cotten and Hayes 1972; Hagberg and Mattsson 1986; Jain and Hasan 1988; Frey 1991; Leggett 1992a). Fruit fly (Oscinella frit L.) is an internal stem feeder causing substantial damage to oat crops. Among wild species, A. pilosa and A. fatua were tolerant to fruit fly (Rodionova et al. 1994). It should be noted that some accessions of diploid species possessed moderate tolerance to the pest. These forms originated mainly from the African continent and from Azerbaijan, e.g., A. canariensis from Spain (the Canaries), A. hirtula from Tunisia, A. longiglumis from Morocco, and A. wiestii from Azerbaijan and Algeria. The level of resistance was, in general, higher among tetraploid species than among the diploids. High resistance to fruit fly has been recorded for the forms of A. macrostachya from Algeria, A. barbata from Azerbaijan, Italy, Greece, France, Iran, and Turkey, and A. vaviloviana from Ethiopia. Among the hexaploids, resistant forms have been found within A. fatua from Russia, Ukraine, Georgia, Azerbaijan, Tajikistan and Poland, A. ludoviciana from Azerbaijan, and A. sterilis from Georgia, France, Italy, Greece, and Morocco. An analysis of the obtained data has shown that the forms with a higher degree of resistance originated from the regions located in the western parts of the natural ranges of wild oat species (Loskutov 2007). The bird-cherry oat aphid (Rhopalosiphum padi L.) does significant damage to oat crops by itself and as the BYDV transmitter. A study of a broad range of species has identified aphid-resistant forms of such diploid species as A. clauda from Greece (Crete Island) and Algeria, A. pilosa from Azerbaijan, A. ventricosa from Algeria, A. longiglumis from Israel and Morocco, A. prostrata from Spain, and A. wiestii from Israel and Iran (Loskutov 2007). Resistance to different aphid species has been found in the tetraploid species A. barbata (Weibull I.G. Loskutov and H.W. Rines 1986; Weibull and Hanson 1986). According to the literature, the perennial outcrossing tetraploid species A. macrostachya is characterized by very high resistance to the aphid (Leggett 1992a). Probably, resistance of this species to aphids may be explained by larger number of cuticle cells in leaves and an increased content of the glutamic acid and decrease in the aspartic acid in the cell sap (Weibull 1988b); it is the reason why larvae develop poorly and excrete less fluid (Weibull 1988a). Two related AC-genome species from Morocco, A. magna and A. murphyi, may be regarded as resistant. The AB-genome species A. agadiriana, A. vaviloviana, and A. barbata were moderately resistant, though the last species was not quite uniform in this respect as the former two. Degrees of resistance within A. barbata strictly depended on the geographic origin: high resistance was displayed by accessions from Russia, Portugal, Spain (the Canaries), Italy, Turkey, Morocco, and Tunisia. All hexaploid species were resistant to the pest: resistant forms within A. fatua were found to originate from Russia, Kazakhstan, France, Albania, Greece, Germany, Slovakia, Poland, Turkey, Iran, Canada, Mexico, and Argentina; all resistant accessions of A. occidentalis originated from the Canaries (Spain); those of A. ludoviciana from Tunisia, Ethiopia, and the US; and resistant forms of A. sterilis originated from Spain, Greece, Turkey, Iraq, Iran, Syria, Israel, Algeria, Morocco, Lebanon, Tunisia, Ethiopia, Kenya, and the US (Loskutov 2007). Cereal leaf beetle (Oulema melanopus L.) causes damage to a plant at different stages of its development and is regarded as one of the most harmful insects affecting cereals. It has been established that leaf pubescence is a trait characterizing resistance to this pest. A study of resistance in American populations of A. fatua has identified some forms from Wyoming and Idaho with a medium resistance to the phytophage (Rines et al. 1980). Resistance of some forms of A. sterilis to the insect is connected with a higher leaf pubescence and with the differences in composition of the cell sap in the sprouts (Steidl et al. 1979). It follows from the above that one of the most important means of creating resistant cultivated genotypes is the interspecific hybridization, which may lead to the introgression of genes into oat cultivars. Such crosses involving wild diploid and tetraploid sources of resistance are possible with the use of genetic carriers, while hexaploid species can directly transfer a trait. 3.5.1.6 Resistance to Abiotic Factors Oat possesses quite a range of physiological traits, which help this crop grow in diverse conditions. The main regions of origin and diversity of the whole genus are predominantly located in the arid zones with insufficient moisture and different degrees of soil salinity and acidity and sometimes with low temperatures in the high mountain regions; therefore, drought and cold resistance, aluminum and salt tolerance, and related traits are characteristic of many oat species. The search for new sources of edaphic resistance among wild relatives of cultivated cereals has acquired special importance, since in most cases, many characters initially possessed by wild ancestors have been lost by cultivated species in the course of evolution. Wild species A. wiestii, A. ludoviciana, and A. sterilis have been found to contain highly xeromorphic forms with hardiness to such unfavorable environmental factors as drought, heat, sharp temperature fluctuations, and certain salt tolerance (Holden 1969; Udovenko 1977; Hagberg 1983). Investigations have shown that the C-genome species (diploid and tetraploid) have a low level of resistance to excessive aluminum and hydrogen ions in the nutrient medium, while the A-genome species with different ploidy levels more often displayed high tolerance to aluminum, and the correlation analysis has proved it. The largest group of tolerant forms belonged to the hexaploid species A. sterilis, A. fatua, A. ludoviciana, and A. occidentalis. All wild oat species have been found to be sources of salt-tolerance regardless of their ploidy level. The most tolerant were the forms of A. fatua from Georgia and Kazakhstan and of A. ludoviciana from Azerbaijan (Loskutov 2007). Another set of characters is related to the edaphic stress-related oat adaptation to low and negative temperatures. Such abiotic characters as cold-resistance and winter-hardiness are very important for the wintering forms of cultivated oats. These properties are most characteristic of the majority of wild species 3 Avena because of their predominantly winter- or semi-winter type of development. A tetraploid perennial outcrossing species A. macrostachya is characterized among other oat species by an increased winter hardiness, which may be transferred to cultivated species (Leggett 1992a; Loskutov 2007). Almost all forms of hexaploid weedy species are cold-tolerant and winterhardy. A study of A. fatua and A. ludoviciana in the field and laboratory conditions has confirmed them to be cold-resistant (Pier 1964; Frey 1991; Leggett 1992a). Hybrids involving this species were cold resistant at the sprouting stage (Aujas and Darmency 1983, 1984). Cold resistance has been recorded for accessions of A. sterilis from Greece, Israel, and Turkey (Ephrat 1962; Hetzler and Dambroth 1990). An analysis of F1 hybrids has found cold resistance to be controlled by recessive genes with additive effect; transgression has been observed in F2; therefore, A. sterilis may serve as a source of alleles of the cold resistance genes (Rajhathy et al. 1966). According to Malzev (1930), another species A. ludoviciana truly belongs to the winter plants, especially its forms from Ukraine (the Crimea peninsula). This species has been included in the program for development of winter oat cultivars in Great Britain (Thomas and Thomas 1970). To sum it up, the range of acid and salt tolerance displayed by wild oat species regardless of their ploidy level is quite wide. All the selected accessions can serve as sources of resistance to the considered abiotic factors, hexaploid forms being able to directly transfer these characters when crossed with cultivated oats. 3.5.1.7 Grain Quality Traits Along with agronomic characters, cultivated oat has good grain quality and green matter traits. At the same time, it is believed that the percentage of quality components in the oat caryopsis can be augmented to a very high level through breeding. Protein. Percentage of protein in oat and its yield unit quite often exceed these traits in other cereals, and the amino acid composition in oat is balanced better indicating good nutrient properties of the crop (Table 3.11). In addition to cultivated species, wild diploids A. pilosa, A. clauda, A. ventricosa, A. longiglumis, A. canariensis, A. damascena, A. hirtula, A. atlantica, and A. strigosa are noted for a high (at a 20% level) protein content in grain (Hoppe and Hoppe 1991; Harder et al. 1992; Leggett 1992a; Miller et al. 1993; Welch et al. 2000; Loskutov 2007). Among the accessions with the highest indices (above 20%), there should be a mention of the forms of A. atlantica (Morocco), A. longiglumis (Morocco), and A. wiestii (Azerbaijan) (Loskutov 2007). Among tetraploid species, a higher content of protein in grain (above 20%) has been demonstrated by the species A. barbata and A. agadiriana (Trofimovskaya et al. 1976; Miller et al. 1993; Welch et al. 2000; Loskutov 2007). In some accessions, the amount of protein with an increased lysine content may reach 30%. Such forms have been found within A. magna and A. murphyi (Ladizinsky and Fainstein 1977; Ladizinsky 1988; Butler-Stoney and Valentine 1991; Harder et al. 1992; Leggett 1992a; Welch et al. 2000; Loskutov 2007). The best indices concerning this trait have been demonstrated by the accessions of A. barbata from Azerbaijan (over 21%) and Portugal (22.9%). The maximum value of protein content in grain, i.e., 25.2%, was displayed by the forms of A. magna and A. murphyi from Morocco (Miller et al. 1993; Loskutov 2007). When transferring these characters to cultivated oats, two backcrosses are sufficient for obtaining stable hexaploid genotypes (Zadoo et al. 1988). In Sweden, an oat breeding program with an elaborate system of crosses and the use of backcrosses have been developed for involving the species A. magna and A. murphyi (Hagberg and Mattsson 1986). When crossing these species with cultivated oats, it has been determined that the genes governing a higher protein accumulation were probably localized in the homeologous chromosomes. The species A. fatua is considered by many authors as a good partner in breeding for higher yield and grain quality (Thompson 1966; Trofimovskaya et al. 1976; Frey 1991; Leggett 1992a). A detailed study of American populations of this species collected predominantly in the North-Central states of the country has identified some forms with an increased content of protein and some amino acids (though the average concentration of protein was lower than in A. sterilis). Individual forms of A. fatua (with protein content above 26%) can serve as donors of these characters (Rines et al. 1980). The highest average values of protein content were demonstrated by A. fatua accessions from Ukraine, Georgia, Azerbaijan, Tajikistan, Poland, and Greece (Loskutov 2007). The hybrid I.G. Loskutov and H.W. Rines Table 3.11 Sources of quality traits in oat species Species A. bruhnsiana A. ventricosa A. clauda A. pilosa A. prostrata A. damascena A. longiglumis A. canariensis A. wiestii A. hirtula A. atlantica A. strigiosa A. barbata A. vaviloviana A. abyssinica A. agadiriana A. magna A. murphyi A. insularis A. macrostachya A. fatua A. occidentalis A. ludoviciana A. sterilis A. sativa Genome Cv Cv Cp Cp Ap Ad Al Ac As As As As AB AB AB AB? AC AC AC? СС? ACD ACD ACD ACD ACD plants produced by crossing A. fatua with cultivated oat had a higher percentage of protein (Reich and Brinkman 1984). The dark-glume forms with grain shattering (the wild type) had a lower protein percentage in the caryopsis and a lower percentage of caryopses in comparison with the light-colored non-shattering forms (the cultivated type) (Luby and Stuthman 1983). According to many authors, the species A. sterilis possesses and transfers to its progeny the character of an increased (above 25%) accumulation in grain of protein with a well-balanced amino acid composition (Zillinsky and Murphy 1967; Briggle et al. 1975; Trofimovskaya et al. 1976; Frey 1991, 1994; Leggett 1992a; Welch et al. 2000; Loskutov 2007). A study of several forms of this species has shown the existence of a strong correlation between protein content, resistance to crown rust, and other traits (Spilde et al. 1974; Popovic 1980). It has been proved that in crosses involving forms of A. sterilis, the content of protein in the grain of the progeny is influenced not only by the presence of nuclear genetic material (Browning Sources of quality Protein Oil þ þ þ þ þ þ þ þ þ þ þ b-Glucan Starch Avenanthramindes þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ þ and Frey 1972) but also by cytoplasm (Rezai and Frey 1989a). A study of a large set of A. sterilis forms has shown that the an increased percentage of protein in the caryopsis and straw was characteristic of the accessions from Libya and Iraq (Eagles et al. 1978). The centers of the highest diversity for this trait were found in the Mediterranean Region, Central Asia, Middle East, and Israel (Rezai 1978). The highest average values have been displayed by the forms of A. sterilis from Iran, Israel, Algeria, Morocco, Tunisia, and Lebanon. A large group of accessions from Israel has been found to stably accumulate as much as 23.1–28.0% protein in grain during the years of the study (Loskutov 2007). Besides, some forms of the hexaploid species A. ludoviciana and A. occidentalis have also been characterized by a higher content of protein in the caryopsis (Trofimovskaya et al. 1976; Miller et al. 1993). The highest average values of protein content in grain (20–23%) have been recorded for the accessions of A. ludoviciana from Azerbaijan, Turkey, Iraq, Iran, 3 Avena Israel, and Algeria. An analysis of protein content in the grain of A. occidentalis from the Canaries (Spain) has shown that this species may be promising in breeding for grain quality (Loskutov 2007). In hexaploid wild oat species, the protein content in grain may be as high as 27–28% (Campbell and Frey 1972) and even reach 35% according to some reports (Frey 1975). A comparison of wild and cultivated hexaploid species has shown that the percentage of protein in the caryopsis cross-sections of wild species was higher, while the content of protein per caryopsis was lower due to the small size of the caryopsis in wild species (Youngs and Peterson 1973). The most promising species from the point of view of the availability of high-protein forms may be A. murphyi and A. occidentalis. Among the forms with high content of protein in the caryopsis, those belonging to hexaploid species A. fatua, A. ludoviciana, and A. sterilis are promising for breeding purposes. An analysis of the long-term data for a correlation between the protein content and the geographic locality of collecting a particular form has shown that the accessions of hexaploid species with the highest content of protein in grain originated predominantly from the Northwest of the African continent (Loskutov 2007). Interspecific hybridization proved to be more efficient in breeding for a higher protein content in grain (Alexander 1975; Axtell 1981; Clamot 1984; McFerson and Frey 1990). When crossing cultivated and wild hexaploid species, protein content and yielding ability were found to be inherited independently (Cox and Frey 1985; Kuenzel and Frey 1985). In both cultivated and wild species, high protein content was inherited through recessive genes with additive effect (Sraon et al. 1975). According to many published data, a large number of forms of wild oat species have been analyzed for this trait (Peterson and Brinegar 1986). This has resulted in the identification of accessions, which are currently used in oat breeding for developing highly productive lines and cultivars with an increased content of protein with a well-balanced amino acid composition in grain (Lyrene and Shands 1975). High protein content in grain is important not only for food but also for forage purposes. At present, the forms of naked oat are used as forage for cattle, especially in horse breeding. To increase protein concentration in grain of these oat species, wild species are involved in the breeding process (Valentine 1987). A study of the nitrogen index (the ratio of nitrogen content in grain to the total nitrogen in the biomass) in A. sativa and A. sterilis has established that this index was on the average higher in the cultivated species, while in the interspecific hybrids, it exceeded that of both parents (Fawcett and Frey 1982). Besides, some forms of wild species had a high protein content in straw and green matter. Such accessions have been found among the tetraploid A. abyssinica and A. magna and hexaploid A. ludoviciana and A. sterilis (Mal 1987). The accessions of A. sterilis collected in southwestern Europe had a higher protein percentage in straw (Rezai 1978). The absence of a connection between protein content in grain and in straw evidences for a possible combination in one genotype of genes controlling high protein content (Campbell and Frey 1974; Frey et al. 1975b). Amino acid composition. Amino acid composition of proteins in cultivated oat is well balanced. Amino acid composition of the high-protein tetraploid species A. magna and murphyi is similar to that of cultivated oat (Rodionova et al. 1994). The content of individual essential amino acids was found to be distributed in the studied wild species as follows: the content of valine was the highest in A. barbata and the lowest in A. fatua, that of methionine was the highest in A. barbata, and that of isoleucine was the highest in A. barbata and A. sterilis. The content of leucine was the highest in A. fatua and the lowest in A. barbata, while the content of tyrosine was higher in A. barbata. All the studied species had the highest values of phenylalanine accumulation in comparison with cultivated oats; the content of glutamic acid in cultivated oat was lower than in A. fatua and higher than in A. barbata, and that of proline was higher in A. ludoviciana and lower in A. barbata. In terms of nutrient qualities, protein of the tetraploid species A. barbata should be noted, and in terms of lysine and other essential amino acids content in protein, hexaploid species demonstrated values that were at the level of cultivated oats (Loskutov 2007). The share of albumins and globulins in hexaploid species A. sterilis, A. ludoviciana, and A. fatua was 1.5–2 times lower than in cultivated species, while, on the contrary, the percentage of the alkali-soluble proteins was higher in the three former species. It means that the total protein nutrient value in wild species was lower than that of cultivated species (Trofimovskaya et al. 1976). According to many authors, A. sterilis has I.G. Loskutov and H.W. Rines and transmits the trait of the well-balanced amino acid composition of protein in grain to its progeny (Briggle et al. 1975; Frey 1991; Leggett 1992a). The correlation analysis has found regularities in accumulation of protein and individual amino acids in oat grain. It should be noted that the content of all essential amino acids (except for methionine) correlates closely and positively with the content of protein (0.78–0.94) and lysine (0.62–0.80). The existence of a correlation between the content of protein and lysine in grain protein has been determined in 60.1% of the cases, thus making it possible to carry out preliminary selection of the high-lysine forms on the basis of total protein in grain (Loskutov 2007). Fats. In addition to protein, oat grain is rich in other chemical compounds and fats in particular (Table 3.11). A search for genes capable of improving this trait in cultivated oat while maintaining the stability of yield level has not achieved the desired results so far. Besides, it has been established that the genes controlling this trait in cultivated and wild species are not allelic (Thro and Frey 1985; Frey 1991). Interspecific hybridization proved to be more efficient in breeding for this trait. In some diploid and tetraploid species, the content of oil in the caryopsis reaches 12–13% (Welch and Leggett 1997). The majority of studied forms of such species as A. clauda, A. pilosa, A. canariensis, A. longiglumis, A. damascene, A. wiestii, A. hirtula, A. atlantica, A. agadiriana, A. barbata, and A. vaviloviana had the caryopsis oil content above 7% (Welch et al. 2000; Loskutov 2007; Leonova et al. 2008). A high content of oil in grain has also been recorded for the tetraploid species A. magna and A. murphyi (Ladizinsky 1988; Welch et al. 2000; Leonova et al. 2008). The highest average values for this trait in A. barbata has been demonstrated by its accessions from Azerbaijan, Spain (the Canaries), and from Italy. The highest average values of oil content in grain have been registered for the forms of A. magna and A. murphyi from Morocco (Loskutov 2007). In A. ludoviciana and A. fatua, the content of oil in grain reached 7–9% (Trofimovskaya et al. 1976; Leonova et al. 2008). The highest average values for this trait were displayed by accessions of A. fatua from Ukraine, Kazakhstan, and Tajikistan. The highest average values for oil content in grain (9.7–11.1%) were discovered in accessions of A. ludoviciana from Azerbaijan, Georgia, and Armenia. The percentage of oil (above 7.8%) in grain of a form of A. occidentalis from the Canaries (Spain) indicated that this species may be promising in breeding for grain quality (Welch et al. 2000; Loskutov 2007). On the average, a hexaploid A. sterilis has been found to have a high fat content (upto 10%) in grain (Thro 1982; Frey 1991, 1994; Leggett 1992a; Welch et al. 2000; Leonova et al. 2008). The largest number of samples with such characteristics has been collected in Israel (Rezai 1978). A group of accessions with oil content in grain in the range of 8.3–10.7% has been found to include forms of A. sterilis from Iraq, Israel, Japan, and Algeria (Loskutov 2007). The percentage of oil in hybrid plants produced by crosses with said species increases (Frey 1991). The dark-glume, shattering forms have been noted to have low percentage of oil in grain and low percentage of grain in comparison with the light-colored, non-shattering forms (Luby and Stuthman 1983). This trait is controlled polygenically and shows incomplete dominance. The additive nature of gene action, high heritability, and a close and positive link between the general combining ability (GCA) effects and oil content in the caryopsis have been noted (Elliott et al. 1985). The hybrids involving cultivated oat may be transgressive (Frey et al. 1975a). The main method of transferring the trait of high oil content from wild to cultivated species is recurrent breeding. Since the alleles for high oil content from A. sativa and A. sterilis are complementary (Thro and Frey 1985), a program to improve the oil content by using recurrent selection was carried out that resulted in increases in groat oil concentration of upto 18% in relatively short time (Branson and Frey 1989a, b; Frey and Holland 1999; Schipper and Frey 1991). Fatty acid composition of oil. The oil contained in grain of wild hexaploids practically does not differ from that of cultivated species: oleic and linolenic acids are the main ones in its composition, the content of the latter being sometimes lower or higher than that of oleic acid. The total polyunsaturated acids fit the amplitudinal range of cultivated species. Therefore, the oil content differentiates the wild from cultivated species more than the fatty acids ratio in the oil (Trofimovskaya et al. 1976). The highest content of oleic acid is characteristic of the diploid species A. damascena, A. longiglumis, A. canariensis, A. atlantica, A. hirtula, and A. wiestii, of the tetraploid ones: A. barbata, A. vaviloviana, A. murphyi, and 3 Avena A. magna, and of the hexaploid species A. occidentalis, A. fatua, A. sterilis, and A. ludoviciana (Welch et al. 2000; Loskutov 2007; Leonova et al. 2008). At the same time, biological activity of such oil is determined by the linoleic to oleic acid ratio, which should equal 1.0. Such a value was displayed by the diploids A. ventricosa, A. clauda, and A. pilosa and by the tetraploid A. vaviloviana (Loskutov 2007). A correlation analysis has shown that an increase in the content of saturated (palmitic and stearic acids) and monounsaturated (oleic) fatty acids in oil of wild oat species will be accompanied by the decrease in the content of polyunsaturated fatty acids, which oxidize easily during grain storage (Loskutov 2007). Crosses of the forms with high and low content of linoleic acid have shown that inheritance of linoleic and oleic acids was oligogenic (Karow 1984). Other authors believe that inheritance of palmitic, oleic, and linoleic acids are controlled polygenically with additive effect and that inheritance is partially dominant (Thro 1982). Starch. An important aspect determining grain digestibility is the presence of starch in it (Table 3.11). A content of amylose comparable with that in cultivated oats has also been recorded in the wild species A. sterilis, A. ludoviciana, and A. fatua. These data evidence closeness of starch composition in cultivated and wild oat species (Rodionova et al. 1994). b-glucans. The (1–3) (1–4)-b-D-glucan, or the nonstarch water-soluble polysaccharide b-glucan, is regarded as a physiologically important dietary component of grain (Table 3.11). The data on this trait in wild oat species are very small as compared to the cultivated ones. Among diploid species, an increased content of b-glucans has been noted for A. strigosa and A. hirtula (4.6–5.5%), A. damascene, A. longiglumis, and A. atlantica. In such tetraploids as A. agadiriana, A. barbata, A. magna, and A. murphyi, this value was around 3.2% on an average (Miller et al. 1993; Leggett 1996; Howarth et al. 2000; Welch et al. 2000). A study of a limited set of accessions of wild species including A. sterilis has shown that all hexaploid species (A. fatua, A. occidentalis, A. byzantina) had a higher content of b-glucans (upto 6%) in grain (Frey 1991; Welch et al. 1991; Cho and White 1993; Miller et al. 1993). Groat b-glucan concentration in wild species showed very wide variation (2.2–11.3%) as there were substantial interspecific and intraspecific differences (Welch et al. 2000). Vitamins. Oat contains different vitamins, including the fat-soluble vitamin E (tocopherol and tocotrienol), which possesses increased antioxidant properties. The data on this trait in wild oat species are extremely poor. A study of the influence of different mutagens on oats has found that the high content of tocopherols in A. ventricosa plants can be explained by a lesser sensitivity of this species to physical and chemical mutagenic damage in comparison with the affined species A. bruhnsiana, which has a low content of tocopherols and a more narrow distribution range in comparison with the former species (Alekperov 1982; Alekperov and Sinitsina 1982). A study of nutritional properties of oats from India has identified a number of species with a decreased content of lignin and silica compounds in green matter thus suggesting their suitability for consumption by animals. Among these species are the diploids A. strigosaand A. ventricosa, tetraploids A. barbata, A. vaviloviana, and A. abyssinica, and hexaploids A. sterilis and A. ludoviciana (Mal 1987). Thus, it has been established that the wild species A. magna, A. sterilis, and A. ludoviciana are the most promising and important ones in terms of grain quality and the transfer of this trait to cultivated oats. Besides, there also exist other sources of various traits related to grain and green matter quality, which may be successfully used for improving these characters in cultivated oats. 3.5.2 Use of Wild Oats in Crop Improvement: Challenges, Approaches, and Successes The tremendous potential of wild Avena species as donors of genes for a wide spectrum of biotic and abiotic traits is evident from the preceding deliberations of numerous species sources harboring resistance for various oat pathogens and wide ranges of variation in other quantitative traits. The transfer, capture, and sustainable use of these traits in oat cultivar development and releases can prove challenging for from genetic techniques to breeding line selection, especially with transfer from lower ploidy species. This section describes genetic and breeding approaches employed with different Avena species as trait sources, breeding line development I.G. Loskutov and H.W. Rines including examples of cultivars released with transferred improved traits, some difficulties and limitations encountered, and how use of molecular markers can facilitate transfer and selection. The ease of transfer and the utility of the variation identified in wild and lower ploidy Avena species accessions depend on the nature of variation, whether qualitative or quantitative, and the genetic relationship between the alien donor and the recipient cultivated species. Qualitative variation, such as disease resistance when controlled by major genes, is often simply inherited and readily scorable independent of genetic background and growth environment. Quantitative variation, such as is observed for many agronomic and seed quality traits, in contrast, is often controlled by multiple genes and its expression is strongly influenced by genetic background and the growth environment. Oat cultivars with a portion of wild oat germplasm in their parentage and with enhanced quantitative traits have been released where the enhanced trait is attributed to the wild oat germplasm component. This attribution is often based on an enhanced level of that component in the wild germplasm donor. The extent of trait contribution, however, and even the amount of wild species germplasm genome present after rounds of crossing and selection cannot currently be documented. The use of gene- and genome-specific DNA markers will not only aid tremendously in the identification and transfer of quantitative trait loci (QTL) for these traits from wild species sources but also enable documentation of their presence and contribution. As discussed in Sect. 3.4, the species of Avena have been assigned into three gene pools – primary, secondary, and tertiary – by Leggett and Thomas (1995) based on the ease of transfer (introgression) of genes from alien species into cultivated hexaploid oat according to the concept of gene pools for cultivated species proposed by Harlan and de Wet (1971). In this system, the primary gene pool consists of all the hexaploid species, the secondary pool of the tetraploid AACC species A. magna, A. murphyi, and A. insularis, and the tertiary pool the diploid species and the remaining tetraploid species. In Avena, the transfer of traits has been mostly from within the primary gene pool. Even there, documented contributions to cultivar development have been restricted primarily to qualitatively inherited major genes for disease resistance where trait detection is more readily accomplished. 3.5.2.1 The Primary Gene Pool All the hexaploid oat taxa, including the most common wild oats A. sterilis and A. fatua, were grouped into a single biological species with cultivated oats by Ladizinsky and Zohary (1971) because of their high interfertility in crosses. Thus, the hexaploids constitute the primary gene pool for transfer of desired traits to cultivated hexaploid oat. Because of the high interfertility, the introgression of traits from the wild hexaploid can be accomplished fairly readily by conventional crossing and backcrossing procedures. However, greater frequencies of meiotic abnormalities, such as univalents and micronuclei, were observed in wild/cultivated species hybrids of A. sterilis/A. sativa by McMullen et al. (1982) and in A. fatua/A. sativa by Luby et al. (1985) than in intraspecific hybrids. These higher frequencies indicate that in spite of high interfertility, there are likely reductions in recombination associated with meiotic irregularities due to chromosomal heteromorphology between the wild and cultivated hexaploid oats. These irregularities could hinder breaking of linkages between useful and deleterious genes during wild to cultivated oat introgression. A. sterilis, the progenitor species of cultivated oat, has been found to be quite a rich source of diverse traits, particularly disease resistance, for use in oat breeding programs (Frey 1985). In the spring, in oat regions of the midwest US and the eastern prairie regions of Canada, and also in the winter oat regions of the southern US, where crown rust (P. coronata f. sp. avenae) periodically can devastate oat production, most oat breeding programs have become reliant on the use of crown rust resistance (Pc) genes from A. sterilis in their cultivar releases. More than 30 of these Pc genes from A. sterilis have been identified and backcrossed into susceptible oat lines to form sets of differentials that are used to monitor changes in rust virulence patterns (Chong et al. 2000; Carson 2008). However, most of the Pc genes used to-date have been major genes providing rust race-specific resistance. Thus, when deployed singly, though initially highly effective in protecting the cultivar, they can rapidly lose their effectiveness due to high selection pressure causing shifts in the rust population’s virulence pattern. Various schemes have been developed over the years to try to extend the effective use of these genes. In the Canadian oat breeding programs, an A. sterilis 3 Avena gene, Pc39, added singly in the cultivar Fidler (McKenzie et al. 1981) provided crown rust resistance that was improved compared to that of other cultivars when the cultivar was released. Later, combining Pc38 and Pc39 in the release “Dumont” (McKenzie et al. 1984) conferred resistance to all known crown rust races at the time. This Pc38–Pc39 combination together with possible other non-identified A. sterilis genes was used in many other Canadian releases and in North Dakota releases including “Steele,” “Valley,” and “Newdak” (McMullen and Patterson 1992). The Pc38–Pc39 combination provided effective resistance until it was finally overcome around 1990 (Chong and Seaman 1991). The addition of Pc68 to Pc38–Pc39 in “AC Assiniboia” (Brown et al. 2001), “AC Medallion” (Duguid et al. 2001), and several subsequent releases provided protection for several additional years, but this combination too lost effectiveness with race shifts to virulence on Pc68 (Chong et al. 2008). This breakdown necessitated a search for additional sources of resistance including new A. sterilis lines for use in combined or stacked combinations. Winter oat breeding programs in the southern US made use of other A. sterilis-derived Pc genes for crown rust resistance including Pc58 in “TAM-0-301” (McDaniel 1974a) and Pc59 in “TAM-0-312” (McDaniel 1974b), two releases from Texas A&M University, and Pc60 and Pc61 in releases by the Coker’s Pedigree Seed Company in South Carolina (Leonard and Martinelli 2005). Pc60 and Pc61 subsequently also were used in spring oat cultivars “Don” (Brown and Kolb 1989a) and “Hazel” (Brown and Kolb 1989b), respectively, released from Illinois. An alternative method of deploying crown rust resistance genes, including numerous ones from A. sterilis, to extend the effective life of individual resistance genes was the “multiline” approach utilized by K.J. Frey, J.A. Browning, and M. D. Simons at the Iowa State University (Browning and Frey 1969). In this approach, different crown rust resistance genes were introgressed into a common oat cultivar or line to form a rust gene composite cultivar of otherwise agronomically similar lines. The deployment of this multiline should then put less selective pressure on the rust population to develop resistance to any particular resistance gene. In the multiline cultivar “Webster,” all nine resistance genes used were from A. sterilis (Frey et al. 1988). While this approach appeared to be effective in delaying or preventing a build-up of virulence on specific genes, it proved too slow and cumbersome to make adequate continued progress on all the other traits involved in a cultivar improvement program and thus has not been widely utilized. In addition to the named Pc genes, many other instances have been reported on transfer of crown rust resistance genes from A. sterilis into oat germplasms and cultivars. Many of these provide adult plant partial resistance and are quantitative and multigenic, and hence more difficult to characterize, but may be less race-specific and hence more durable in effectiveness (Simons 1985). For example, Hoffman et al. (2006) have shown that the Pc58 resistance of “TAM-0-301” entails at least three genetically separable components including one showing possible nonrace-specific partial resistance. Crown rust resistance from A. sterilis has been used in oat improvement in other countries besides the US and Canada, either from direct crosses with A. sterilis or indirectly using A. sterilis-containing germplasm from the US or Canada. Of particular note in this regard is the likely presence in various South American cultivars with Pc58, Pc59, Pc60, and P61 introduced through the Quaker International Oat Nursery, which has been grown for many years in several South American countries (Leonard and Martinelli 2005). Two genes, Pg13 and Pg15, conferring resistance to the other major rust of oat, stem rust (P. graminis f. sp. avenae), are included in the set of differentials currently used to characterize stem rust virulence in the US and Canada (Fetch and Jin 2007). Pc13 combined with Pg2 and Pg9, when used in developing “Dumont” (McKenzie et al. 1984) and several subsequent cultivar releases from the Winnipeg group and in “Steele” (McMullen and Patterson 1992) and subsequent releases from North Dakota, provided effective resistance to the prevalent stem rust races in those regions for several years. However, a rapid rise in prevalence of races with virulence on Pg13 in those regions in the late 1990s necessitated a search for new resistance gene sources (McCallum et al. 2000). Screening of almost 7,000 A. sterilis accessions failed to identify any source with strong resistance to the current prevalent stem rust race in that region, but resistance was found in accessions of lower ploidy oat species (Gold Steinberg et al. 2005). The use of A. sterilis as a source of resistance to oat powdery mildew (Blumeria graminis (DC.) Speer I.G. Loskutov and H.W. Rines f. sp. avenae Em. Marchall) in Britain and continental western Europe was included in a review by Roderick et al. (2000). Powdery mildew is described as the most important foliar pathogen of oats in Britain and in the cooler, humid regions of western Europe. Resistance from A. sterilis (var. ludoviciana) Cc4346 was introduced in the cv. Mostyn in Britain; however, the effectiveness of this race-specific gene was overcome within a few years by a shift in pathogen virulence, although it remained effective for a few additional years in continental Europe. Similarly, the release of cv. Maris Tabard with the resistance gene from an A. sativa  A. sterilis (var. ludiviciana) hybrid resulted in a pathogen virulence shift within a few years. An apparently more durable form of powdery mildew resistance expressed as a partial or adult plant resistance was discovered in the line PC54, which had been developed with a crown rustresistant gene, Pc54, differential by backcrosses of A. sterilis CAV1832 into A. sativa cv. Pendak (Sebesta et al. 1993). This source became the main for powdery mildew resistance deployed in British and European oat breeding programs (Roderick et al. 2000). Resistance transferred from A. sterilis into cultivated oats has also been documented for cereal cystnematode Heterodera avenae Woll. (Cook 1974). Nullisomic analysis indicated that the dominant resistance gene in the oat cultivar “Panema” derived from A. sterilis line I.376 appeared to be at the same locus as the one in cv. “Nelson” derived from A. sativa CI 3444 (Chew et al. 1981). Nematode resistance from A. sterilis was also used in developing cultivars at Svalof, AB, Sweden (Mattsson 1988). In addition to being a rich source of genes for disease resistance, A. sterilis accessions have been characterized, which have other agronomic and seed quality traits of value in cultivated oat improvement. Most of these traits, however, are quantitative in nature, controlled by multiple genes and with expression influenced by the genetic background and the environment. Thus, the transfer of these traits into a desirable cultivated oat type is much more challenging than that for qualitative major genes, which often can be introgressed simply by backcrosses to a recurrent parent cultivar with minimal impact on other traits of the recipient. In his review on oat improvement, J. B. Holland (1997) pointed out that transfer of a polygenic quantitative trait from a wild oat species usually requires larger amounts of wild germplasm to be maintained in the resulting breeding lines than transfer of a single gene trait. Thus, the transfer of quantitative traits fits more into the concept developed by Simmonds (1993) of “incorporation” of exotic germplasm versus simple “introgression” of a single trait. Another problem for incorporation of quantitative traits from wild germplasm besides potential linkage drag of deleterious genes is the same as for incorporation of such traits from any germplasm source – a resulting undesirable correlated change in other traits in the resulting lines. For example, groat (karyopsis) protein as high as 35% was identified in some A. sterilis accessions (Campbell and Frey 1972; Ohm and Patterson 1973; Frey 1983) but proved difficult to capture in high grain yielding breeding lines due to the well-known negative association between these characters in cereals (Simmonds 1995). This complication arises due to competition between physiological processes for a limited pool of nitrogen and carbon metabolites. Also, apparent high levels of grain components such as protein, oil, b-glucan, or other nutrients are often expressed on a percentage basis such that thin-kernels with low starch content appear deceivingly favorable. In spite of these problems, germplasm and breeding lines with enhanced levels of seed composition traits have been produced from A. sterilis–A. sativa hybridizations (Frey 1992). In his review, Holland (1997) pointed out that recurrent selection has proven to be a technique particularly well-suited for incorporating genes from A. sterilis into adapted gene pools due to the opportunities to break linkages to undesirable traits through successive rounds of recombination and selection. He then described two examples from the extensive work of Frey and his students at the Iowa State University on the use of recurrent selection using A. sterilis germplasm to generate high protein and high oil oat breeding lines. Several progressive studies were involved in the incorporation of high groat protein from A. sterilis including the demonstration that some high-protein genes from A. sterilis were different from and complementary to those in A. sativa (Cox and Frey 1985), the identification of several mating lines involving both A. sterilis and A. sativa germplasm in which there was little or no negative correlation between grain protein percentage and groat yield (Kuenzel and Frey 1985), 3 Avena AU20 AU21 and the selection of progeny from those matings and their use as the source parents for cycles of recurrent selection for high grain protein yield (grain yield  protein percentage) (McFerson and Frey 1991; Moser and Frey 1994). A similar progressive set of experiments were conducted to use A. sterilis germplasm in the development of high groat oil concentration oat breeding lines with first the demonstration that genes for high groat oil content from A. sterilis are complementary to those from A. sativa (Thro and Frey 1985), then crossing of high oil A. sterilis accessions to high oil A. sativa lines followed by crosses to agronomically superior A. sativa cultivars with cycles of recurrent selection for high oil content with independent culling for agronomic adaptation and cultivated plant type (Branson and Frey 1989a, b). These efforts resulted in lines after cycle 6 with oil content over 16% (Schipper and Frey 1991). The presence of yield enhancing genes from A. sterilis were reported by Frey and Browning (1971) based on increased yields of some of the lines derived from crosses made to introgress crown rust resistance genes from A. sterilis into A. sativa. Enhanced yield was also found in backcross F2 generations of several other A. sterilis  A. sativa crosses by Lawrence and Frey (1975). Further studies of such materials indicated that the enhanced yield was likely attributable to enhanced growth rate (Takeda and Frey 1976), increased biomass (Cox and Frey 1984a, b), and greater leaf area duration (Brinkman and Frey 1977; Bloethe-Helsel and Frey 1978). Several cultivars with improved traits and containing large amounts of A. sterilis germplasm have been released including “Sheldon” (Frey 1992) and Ozark (Bacon 1991). In these lines, high yield potential and, in Ozark, winter hardiness have been attributed, at least in part, to contributions from the A. sterilis component. Similarly, although no specific genes for barley yellow dwarf virus (BYDV) tolerance (inherited as a polygenic trait) were identified, the finding of BYDV tolerance or resistance in almost half of 1,718 A. sterilis accessions tested led Comeau (1982) to postulate that many of the recent cultivars in USA and Canada derive some BYDV resistance factors from A. sterilis. Enhanced yield was also observed in early backcross generation lines, which contained A. sterilis cytoplasm when the lines were compared to derived lines from reciprocal crosses involving the same A. sterilis–A. sativa parents but with A. sativa cytoplasm (Robertson and Frey 1984). This observation led them to propose use of A. sterilis cytoplasm for oat cultivar improvement. However, failure to find evidence of a consistent nuclear–cytoplasm heterotic effect across numerous A. sterilis–A. sativa matings (Beavis and Frey 1987) and in later backcross generations of A. sterilis–A. sativa matings (Rines and Halstead 1988) indicated that the positive effect of the A. sterilis cytoplasm was specific depending on the accession combination and the A. sterilis nuclear genes retained in each line. The other common wild hexaploid oat, A. fatua L., has been used to a much lesser extent than A. sterilis as a germplasm source for oat improvement. This reduced use is probably because of its lack of identified major genes for disease resistance and overall lack of diversity of traits as found in A. sterilis. A. fatua germplasm was a major component of releases of the cultivars “Rapida” (Suneson 1967a), “Sierra” (Suneson 1967b), “Montezuma” (Suneson 1969), and “Mesa” (Thompson 1967). The use of locally collected A. fatua as parents provided desired adaptation characteristics for the arid regions of the southwest US including extreme earliness in Rapida and Montezuma. Stevens and Brinkman (1986) were less successful in the use of A. fatua accessions to improve yield performance in crosses to Midwest US cultivars. One backcross selection did outyield its recurrent parent but lacked straw strength and crown rust resistance as required for cultivar release. Several dwarfing genes were identified in short statured A. fatua plants collected in Japan and the surrounding areas of eastern Asia when these plants were crossed to cv. Kanota by Morikawa 1989 and Morikawa et al. (2007). However, when one of these genes was used in further crosses by Milach et al. (1998), the resulting dwarf phenotype was found to be too extreme to be directly used in cultivar development. Further efforts to identify appropriate modifier genes or the use of other of the identified dwarfing genes might prove useful in developing reduced height oat cultivars. An uncharacterized gene (or genes) for dormancy in A. fatua accessions was used by Burrows (1986) to develop experimental lines (termed “dormants”) of cultivated oat that could be planted in the fall, lie dormant over winter, and then germinate in early spring to take advantage of a longer growing season in the northern regions I.G. Loskutov and H.W. Rines where oats do not successfully overwinter. Adequate synchrony of germination combined with good cultivated oat phenotype proved difficult to attain for use in cultivar release. 3.5.2.2 The Secondary Gene Pool Leggett and Thomas (1995) defined the secondary gene pool as the AACC tetraploid species A. magna (maroccana) and A. murphyi based on observations that, although in hybridizations with A. sativa the F1 plants are highly self-sterile, F1 female fertility enables crossing to hexaploid to produce low seed set, and pairing between chromosomes of the tetraploid and hexaploid species seems sufficient to allow recombination to occur. A. insularis, a more recently discovered AACC tetraploid (Ladizinsky 1998) should also be included in this secondary gene pool. The capability to transfer genes from the AACC tetraploid to hexaploid cultivated oat was indicated by the recovery of derivatives of backcrosses of the pentaploid F1 having 42 chromosomes but with traits characteristic of the tetraploid parent (Ladizinsky and Fainstein 1977; Thomas et al. 1980a). The successful introgression of crown rust resistance from an A. magna accession into a hexaploid cultivated oat germplasm was accomplished by Rothman (1984) through the use of a synthetic hexaploid. The synthetic hexaploid was derived from a colchicine treated F1 hybrid between diploid A. longiglumis accession CW57 and A. magna accession CI 8330. Although the initial C1 (progeny of colchicine-treated F1) plant set few seed, a C6 segregants with cultivatedtype spikelet components and stable fertility was recovered, perhaps through accidental outcrossing. This germplasm containing the resistance gene Pc-91 (Rooney et al. 1994) was used in developing the cultivar HiFi (McMullen 2005), which, due to the presence of Pc91 together with some unidentified Pc genes, has retained its effective resistance for several years (Chong et al. 2008). Features of A. magna that provoked the initial interest in transfer of genes to cultivated oats was the large groat size and high groat protein content (over 25%) in certain accessions (Ladizinsky and Fainstein 1977; Thomas et al. 1980a). In spite of extended crossing, backcrossing, and selection efforts, successful incorporation of these polygenically inherited traits into high-yielding cultivars has not proven possible (J. Valentine personal communication, Aberystwyth Univ., UK). As an alternative to trying to transfer these complex polygenic traits into hexaploid cultivated oat, Ladizinsky and Fainstein (1977a) proposed transfer of more simply inherited domestication traits from A. sativa into A. magna and A. murphyi to produce a domesticated tetraploid oats. Ladizinsky (1995) reported transfer of the characteristics of nonshedding spikelets, glabrous and yellow lemma, and reduced awn formation into tetraploids with each of the characteristics segregating in an apparent single gene manner. He further pointed out that such transfers into otherwise A. magna and A. murphyi genetic backgrounds might make domesticated derivatives more successful than common oat in the warm habitats of Morocco and Spain where these wild tetraploid species grow naturally. 3.5.2.3 The Tertiary Gene Pool The tertiary gene pool as defined by Leggett and Thomas (1995) consists of all the diploid Avena species and the tetraploids A. barbata, A. vaviloviana, A. abysinnica, and A. macrostachya. Characteristic of this more difficult to exploit group is that members do not readily hybridize with A. sativa to produce F1 plants, F1 plants when produced are highly sterile both in self-fertilization and in backcrosses to the F1, and the introduced desired traits are usually difficult to introgress into stable cultivated breeding lines free of accompanying deleterious genes. Use of the lower ploidy parent as female in crosses usually enhances the frequency and quality of seed set (Rajhathy and Thomas 1974). Even then, embryo rescue is often required in many diploid  hexaploid crosses to recover F1 plants. Some level of fertility in these highly sterile interspecific F1 plants, presumably resulting from a lack of chromosome homology and subsequent lack of chromosome pairing, is often attained by treating the plants with colchicine to double the chromosome number, thus producing plants with the full sets of chromosomes from both parents. Backcrossing of these chromosome-doubled lines to A. sativa as recurrent parent with selection for the introduced desired trait often produces gradually increasing fertility to lines similar to the recurrent parent with the trait introgressed or with the trait 3 Avena present on an added or substituted chromosome or chromosome pair. Examples of successful trait introgression using synthetic octaploids from embryorescued colchicine doubled F1 plants from diploid  hexaploid crosses include introgression of powdery mildew resistance from A. pilosa by Hoppe and Kummer (1991), now in the recently released cultivar “Champion” (M. Herrmann, BAFZ, Gross Lusewitz, Germany, personal communication 2009), and crown rust resistance Pc94 by Aung et al. (1996), now in the cultivar “Leggett” (Chong et al. 2004). Several other “bridging” schemes have been used to transfer genes, usually for rust resistance, from diploids to A. sativa. These involve incorporating the resistance into a tetraploid or synthetic hexaploid that will produce a viable F1 in crosses to A. sativa and include production of a colchicine-doubled autotetraploid of the diploid (Zillinsky and Derick 1960), introgression of the rust gene from the diploid into a tetraploid species (Zillinsky et al. 1959), and construction of a synthetic hexaploid by crosses of the diploid to a tetraploid followed by colchicine doubling to construct a synthetic hexaploid. These latter 2x þ 4x synthetic hybrids have been made both with AABB (AAA0 A0 ) tetraploids such as A. abysinnica (Brown and Shands 1954; Forsberg and Shands 1969a, b) and AACC tetraploids A. magna (Rothman 1984) and A. murphyi (Rines et al. 2007). The 2x · 4x synthetic Amagalon from A. magna  A. longiglumis also permitted access to the crown rust resistance gene Pc91 (Rothman 1984) from the tetraploid A. magna, now in cv. HiFi (McMullen 2005). The next difficulty frequently encountered in gene transfer from a diploid or tetraploid oat species into common cultivated oat is to integrate that gene into breeding lines stable for transfer of the added gene through generations and free of deleterious linkage effects. Dyck and Zillinsky (1963) reported two crown rust resistance genes originally from A. strigosa CD3820 present in different selections from crosses of a derived tetraploid to A. sativa. One of these, Pc23, appeared to be completely incorporated into the normal sativa lines and was transmitted in a stable fashion. The other, Pc15, was inherited in an unstable fashion. They suggested that, based on cytological observations of varying frequencies of pairing between A. strigosa and A. sativa chromosomes in A. strigosa  A. sativa hybrids, there were segments of diploid chromosomes (e.g., the one carrying Pc15) not fully compatible with the sativa chromosomes and thus responsible for the irregular meioses. Comparative analyses between molecular marker maps of A genome diploids and A. sativa revealed larger syntenic regions to A. sativa linkage groups with some of the diploid linkage groups than with others (O’Donoughue et al. 1995; Portyanko et al. 2001). Also, Jellen et al. (1995) found that certain chromosomal linkage groups tended to remain more syntenic across cereals than others. Thus, the possibility or ease with which a foreign gene (e.g., from A. strigosa) is incorporated cleanly into a chromosome of the recipient species likely depends on the location of the gene in the donor genome and the retained homoeology of that donor chromosome or chromosome segment to a chromosome of the recipient species. For example, Rines et al. (2007) obtained normal male and female transmission of a crown rust resistance gene (Pc94) in 42-chromosome derivatives in transfers from A. strigosa CI6954SP into an “Ogle” oat background. Loss in further backcrosses of a molecular marker SCAR94-2 (developed by Chong et al. 2004) linked about 5 cM from Pc94 in other backcross lines indicated that meiotic recombination was occurring in the region. Field tests of backcross 6 lines revealed no evidence of linkage drag of any detrimental traits (H. Rines unpublished). In contrast, several efforts were made over years to incorporate into stable lines the Pc15 resistance from A. strigosa CD3820 by selfing or backcrossing of strigosa-derived materials. Paired cytological and resistance transmission studies revealed that the resistance was always associated with a retained alien addition, substitution, or telosomic chromosome and transmitted unstably, usually only through the female gamete. Irradiation of an alien monosomic substitution allowed recovery by Sharma and Forsberg (1977) of a stably transmitting line, presumably from translocations from the alien substitution chromosome to a non-homoeologous chromosome. The performance of three cultivars “Centennial,” “Horicon,” and “Dane” with resistance derived in this manner indicates that derivatives can be produced by this approach and further selection with no accompanying significant deleterious effects (Forsberg 1990). Difficulties have also been encountered in transferring desired genes cleanly from tetraploid species of this secondary gene pool, again presumably due to chromosomal heteromorphology between the donor species and A. sativa. Attempts to transfer mildew I.G. Loskutov and H.W. Rines AU22 resistance from tetraploid A. barbata (Cc4897) to cv. Manod through backcrossing and selection resulted only in lines with the resistance carried on an alien addition chromosome (Thomas et al. 1975). Irradiation of the addition line with a CO60 source enabled recovery of a resistant translocation line with normal transmission of the resistance in the “Manod” background, but the translocation showed irregular transmission in certain other cultivar backgrounds. This translocation was shown to involve exchange between non-homoeologous chromosomes (Aung and Thomas 1978). Transfer of stem rust resistance from A. barbata by irradiation of alien chromosome additions was similarly accomplished by Brown (1985) producing relatively stably transmitting translocation lines, but with accompanying yield reductions, presumably due to the presence of deleterious genes on the translocated alien segment. More stably transmitting mildewresistant breeding lines were produced by Thomas et al. (1980b) who employed through crosses the action of a “suppressor” of non-homoeologous chromosome pairing present in A. longiglumis CW57. The use of CW57 to induce homoeologous pairing of desirable alien variation into cultivated oat and thus enhanced introgression is discussed by Thomas and Al-Ansari (1988). That the diploid oat component of the “Amagalon” synthetic hexaploid in the earlier described transfer of crown rust resistance from A. magna by Rothman (1984) was A. longiglumis CW57 may account for his success in the recovery of a stable sativa-like resistant derivative. The CW57 line was also used to facilitate transfer of a dominant gene conferring mildew resistance from diploid oat A. prostata (Griffiths 1984; Morikawa 1995). Successful introgression of powdery mildew resistance from the perennial tetraploid oat A. machrostachya, however, was accomplished simply by various crosses and selection (Yu and Herrmann 2006). Of interest relative to the degree of homology of an introduced alien chromosome segment relative to chromosomes of the recipient is not only its initial pairing and recombination with one of the recipient cultivated oat chromosomes but also the disruptive effect the introgressed segment may have on meiotic pairing once it is introgressed. Wilson and McMullen (1997a, b) reported that the introgressed A. sterilis crown rust resistance gene Pc38 was located on one chromosome in the cultivar “Steele” but on a different chromosome in cultivar “Dumont” such that in crosses of “Steele”  “Dumont” the two sites could segregate producing progeny with 0 to 4 copies of Pc38. The alternative site in “Dumont” apparently was generated as a result of a reciprocal interchange presumably involving homoeologous sativa chromosomes. Similarly, the location of another introgressed alien chromosome segment, Pc94 from A. strigosa CI6954SP, has been found at independently segregating sites in various backcross derived lines, again indicating possible occurrence of a translocation between homoeologous sativa chromosomes caused by abnormal meiotic pairing involving the introgressed alien chromosome segment (H. Rines unpublished). Another obstacle that can arise in interspecific trait transfer and which can occur across all levels of ploidy transfer is a suppression or inhibition of expression of the introduced trait. This suppression may be either a gene-specific or a general species-specific suppression and has been observed in many crops including wheat (Singh et al. 1996). A crown rust resistance gene Pc38, or some factor closely linked to it, was reported to suppress the resistance of another A. sterilis-introduced gene Pc62 (Wilson and McMullen 1997a, b) and also a resistance gene Pc94 introduced from A. strigosa (Chong and Aung 1996). Rines et al. (2007) reported a suppressor of Pc94 being co-introduced from A. strigosa CI6954SP that segregated from it in backcross derivatives. This suppressor also inhibited Pc62 but differed from the Pc38-associated suppressor in other Pc-gene specific suppression (Rines et al. 2008). Apparent general species-specific suppression was reported by Rines et al. (2007) where excellent crown rust resistance in A. murphyi P12 was suppressed in crosses and backcross derivatives of A. murphyi P12  A. sativa “Ogle.” A similar lack of expression of the A. murphyi resistances in crosses to five other susceptible cultivars indicated a general suppression by A. sativa (Rines et al. 2008). A lack of resistance expression was also found in hybridizations to A. sativa of stemrust-resistant A. strigosa PI258731 (H. Rines unpublished) and BYDV-resistant A. strigosa (Ladizinsky 2000). 3.5.2.4 Use of Molecular Markers Although genes for many traits, particularly disease resistance, have successfully been introgressed from wild species into cultivated oat by backcrossing with selection for the trait at each generation, the process 3 Avena could now become much more efficient (efficacious) if one were able to use molecular markers to facilitate the transfer. Markers could be used to both identify the gene of interest, being either tightly associated with the gene or a part of it, and to select for maximum recovery of the recipient cultivated oat parental genome. Linked molecular markers have been found for several introduced genes (as summarized in Rines et al. 2006), but the identification has usually occurred only post-introgression for use in further transfer to other breeding lines. Whereas tightly linked or genespecific markers are valued for selection for the introduced trait, also of value are markers identified in the surrounding region of the donor genome segment. Post-introgression selection against such markers can allow recovery of recombinants with smaller alien segments lacking possible deleterious genes linked to the gene of interest. For example, powdery mildew resistance and stem rust resistance have been introduced into stably transmitting breeding lines, but negative agronomic effects were associated with them (Brown 1985; Valentine et al. 1994), presumably due to linked deleterious genes from A. barbata. The effective transfer of the many possible quantitative multigenic traits identified in wild Avena species will require marker use to identify and track QTLs governing these traits. Also, selection for maximal recovery of the desired cultivar background in any transfer effort will require a large number of well-distributed markers. Thus, the capability to capture and utilize all the potential in wild oat species for cultivated oat improvement depends on the development of cheap, high-throughput markers allowing ready whole genome scans and well characterized molecular linkage maps at all ploidy levels. Many of the trait-associated markers identified to date in oat have been difficult or expensive to assay and with limited polymorphisms in possible recipients. 3.6 Avena as Weeds and Invasive Species Some oat species are weeds infesting cereal crops (see Sect. 3.1.1.2). Among the diploid species, this is A. longiglumis, represented by populations of tall, vigorous plants (up to 2 m tall) weeding crops on fertile, well moistened sandy soils, and A. atlantica. Both species weed cereal crops in Morocco (Leggett et al. 1992). Some other diploid species occur as ruderal weeds only along the roads or around human dwellings. On the Ethiopian plateau, the tetraploid A. vaviloviana is a common weed in wheat and barley fields, reaching up to 2,200–2,800 m (Ladizinsky 1975). A large population of A. magna (upto 2 m tall) has been found in Morocco on alluvial soils as a weed of cereal crops (Leggett et al. 1992). Aggressive nature of this species has been later confirmed by other researchers (Saidi and Ladizinsky 2005). Among all tetraploid species, A. barbata is the most noxious weed that grows in all Mediterranean countries. It invades fields of all agricultural crops, and in the east, its natural range stretches through Asia Minor, Iraq, and Iran to the Himalayas. It should be noted that according to the opinion of Malzev (1930), in the early twentieth century, this species was entirely wild and did not weed agricultural fields. The hexaploid species A. sterilis, A. ludoviciana, and A. fatua are noxious weeds, especially A. fatua, against which herbicides are being developed. These invasive species infest vast territories in the basins of the Mediterranean, Black and Caspian seas, and extends through the Southwest Asia to the easternmost point of the Asian continent, occupying all agricultural regions. It should be noted that in the American continent, south of Africa, Japan, Australia, and countries of Oceania, A. barbata, A. sterilis, A. ludoviciana, and A. fatua are noxious adventitious weeds (Malzev 1930; Whalley and Burfitt 1972; Yamaguchi 1976; Rines et al. 1980; Dillenburg 1984). Gene flow via pollen dispersal may occur within the oat crop-wild-weedy complex, which consists of domesticated oat and its two fully interfertile hexaploid wild relatives A. sterilis and A. fatua. There is evidence of hybridization between the crop and the wild species under natural conditions. Although the levels of outcrossing are usually low, the potential for gene flow and introgression into wild oats is substantial because of their widespread occurrence. Thus, the cultivation of transgenic cultivars of oats and other cereals in future may lead to the transformation of these noxious weeds into super-weeds due to gene flow from transgenic crops. I.G. Loskutov and H.W. Rines 3.7 Recommendations for Future Actions The international community faces the task of raising funds and designing programs of safeguarding other oat wild species: A. clauda (in Greece, Bulgaria, Turkey, Algeria and Morocco), A. pilosa (Greece, Turkey, Algeria and Morocco), A. ventricosa (on Cyprus and in Algeria), A. bruhnsiana (in Azerbaijan), A. damascene (Syria and Morocco), A. prostrata (Spain and Morocco), A. atlantica (Morocco), A. agadiriana (Morocco) and A. macrostahya (in Algeria). Being a unique component of the Earth’s biodiversity, each of these species contains genetic information that can be used in practical oat breeding (see Sect. 3.2.1). 3.8 Conclusions There is considerable interest in extending the range of cultivated oat through the incorporation of genes from the wild oat species. A number of considered wild species are reflected in a wide range of botanic, ecological, and genetic diversity. The results of presented researches of wild Avena species made it possible to display intraspecific diversity on all the characters involved. Numerous researches in this direction and practical results of oat breeding have evidenced that utilization of wild species is the most promising trend of oat breeding, capable of broadening genetic base, and reducing genetic erosion of this crop. Acknowledgments Igor G. Loskutov is grateful to Ekatherina D. Badaeva (Engelhardt Institute of Molecular Biology, Moscow, Russia), Alexander V. Rodionov (Komarov Botanical Institute, St. Petersburg, Russia), Irina N. Anisimova (Vavilov Institute of Plant industry, St. Petetrsburg, Russia), and Ronald L. Phillips (Department of Agronomy and Plant Genetics, Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, USA) for critical reading of thе manuscript and making valuable suggestions and wish to extend thanks to translator of VIR Mr. Sergei V. Shuvalov. 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(1985, 1986), Nocelli et al. (1999), Rajhathy and Dyck (1963), Roshevitz (1951), Tinker et al. (2009), Vavilov (1997). Kindly cite them in the text or delete them from the list. AU24 Please update the reference Maggioni et al. (2009) AU25 Please update the reference Peng et al. (2009). AU26 Please update the reference Shelukhina et al. (2009).