Eriobotrya japonica (loquat)

Originating in China but grown widely, the loquat tree may only be grown in a few countries as a fruit crop, but is cultivated in many countries as an ornamental tree. Eriobotrya japonica is a small evergreen tree, occasionally up to 10 m. There are two large fruit producing regions: eastern to southern Asia and the Mediterranean basin. Generally, loquats are found between latitudes 20 and 35° north and south but can be cultivated up to latitude 45° under maritime climates. Loquat is a long-lived tree and orchards over 90 years old remain productive. The time of flowering is slightly unusual for fruit crops, occurring during autumn and winter. Trees are self-fruitful, although reports have suggested that cross pollination can improve fruit set values. As the loquat develops, it becomes less hairy and turns from green and cream to yellow and orange. The fruit ripens in late spring and the following summer and is soft, bruising easily when fully ripe. Loquat fruit has a useful position in the marketplace, arriving before most other spring fruit crops. The fruit taste can be rather sharp, with a fresh apple-like flavour, and fruits are eaten fresh, stewed or processed into preserves, jellies, juices, cordials or confectionary. Seeds are rich in starch (20%) and have been used to make wine.

Principal sources: Janick and Paull (2008), Jackson et al. (2010)

Eriobotrya japonica is a perennial tree species that has been widely grown as an ornamental tree and for its sweet, edible fruits. Mammals and birds feed on the fruit and disseminate the seeds into the wild, facilitating the establishment of new plants in areas outside cultivation. Once established, this species has the potential to form tall stands that replace native vegetation. Currently it is listed as invasive in the Mediterranean region, Australia, New Zealand, Réunion, Hawaii, Chile, Galapagos Islands, Trinidad and Tobago and South Africa.

Rosaceae is a family of 92 genera and 2,805 species of herbs, shrubs and trees, distributed worldwide but especially diverse in the northern hemisphere (Stevens, 2019). This family comprises important species often used as ornamentals and for their edible fruits (i.e., Potentilla, Prunus, Geum, Alchemilla, Sorbus, Spiraea and Rosa). Eriobotrya is a small genus comprising between 15 and 22 species, most of them originating in southern China, the rest in South-East Asia (Janick and Paull, 2008). The number of Eriobotrya species is under dispute and the opinions of authors in different countries vary. Eriobotrya is often confused with Mespilus, and sometimes with Crataegus and Photinia.

About 800 E. japonica cultivars have been developed. Based on their origin, two groups can be distinguished: (1) the Chinese group with large, pyriform, deep-orange fruit and (2) the Japanese group with small, slender, light-coloured fruit (Orwa et al., 2009).

Indigenous to south-eastern China and Japan, where it has been cultivated for centuries (Hiep and Verheij, 1991; Flora of China, 2016; USDA-ARS, 2018), loquat is now widely grown across India and South-East Asia, the East Indies, Australia, New Zealand, Madagascar, the Mediterranean region (particularly Spain and Turkey) and South Africa. Although it was introduced as a horticultural tree, it can be found naturalized in India, southern Asia, the Mediterranean region, Australia, New Zealand, Africa, North, Central and South America, the West Indies and on many islands in the Indian and the Pacific Ocean (Hiep and Verheij, 1991; Broome et al., 2007; Orwa et al., 2009; Acevedo-Rodríguez and Strong, 2012; Davidse et al., 2015; PIER, 2016; PROTA, 2016; USDA-ARS, 2018). Generally, loquats are found between latitudes 20° and 35° north and south, but can be cultivated up to a latitude of 45° in maritime climates (Janick and Paull, 2008).

It is thought that E. japonica has been cultivated in Japan and China for over 1,000 years. The botanist E. Kaempfer first described and introduced this species to the western world in 1690. Later, in 1712, C.P. Thunberg provided a more elaborate description. In Europe, this species was planted in the National Gardens in Paris in 1784, and plants taken from Canton (China) were planted in the Royal Botanical Gardens at Kew (England) in 1787. By 1818, cultivation had spread across England, Malta, Algeria and the Near East (Morton, 1987).

In South America, Central America, Mexico and the United States (i.e., California), this species has appeared in cultivation and collections since 1867. It was quite common as a small-fruited ornamental in California gardens in the late 1870s (Morton, 1987). In the West Indies, E. japonica appears in herbarium collections made in 1899 in Puerto Rico and in 1926 in Cuba (US National Herbarium, 2019).

In Hawaii, it is thought that E. japonica was introduced by Chinese immigrants (Morton, 1987). By 1990, Wagner et al. (1999) noted that it occasionally escapes from cultivation in Hawaii Volcanoes National Park. By 1995, it was reported as naturalized on the island of Kauai (Lorence et al., 1995).

Eriobotrya japonica naturally spreads by seed. In cultivation, trees can also be propagated by cuttings (Gilman et al., 2013).

Within its native distribution range E. japonica grows in valleys and forests (Flora of China, 2016). In Australia, it can be found growing in coastal areas, in dry sclerophyll forests and along waterways (Weeds of Australia, 2016). In Hawaii it can be found naturalized in moist and wet areas, in mixed mesic forests, rainforests and along roadsides (Lorence et al., 1995; PIER, 2016). In New Zealand, this species can be found naturalized in disturbed forests and shrublands, hillsides and near sites of cultivation (Webb et al., 1988; Weeds of New Zealand, 2016).

In Japan, many insect pests and diseases damage loquat, and although only a few are serious enough to require prevention measures, these can be difficult to control. Control is mainly by chemical pesticides, but every effort is devoted to keeping loquat trees vigorous by management practices. In China, the loquat suffers from few diseases. The most severe disease across China, Japan and Spain is caused by Rosellinia necatrix. Drenching the soil with a solution of Bavistin [carbendazim] 50% wettable powder (WP), Benlate [benomyl] 50% WP or Basamid [dazomet] 85% WP and then covering with transparent polyethylene were potential measures for effective control. Fumigation tests in Florida, USA, with methyl bromide at normal atmospheric pressure indicated that 16 g/m³ for 2.5 h at 22.8°C or 32 g/m³ for 2.5 h at 18.3-22°C gave adequate protection to greenhouse grown loquat for latania scale (Hemiberlesia lataniae).

Across the major production areas, the most serious insect pests are Aprona japonica (Japan), Grapholita molesta (China and Japan), Nippolachnus piri (Japan), Phalera flavescens (Japan) and Rhynchites heros (Japan). The most serious pathogens, other than R. necatrix, include Cercospora eriobotryae (China, Spain, Japan), Entomosporium eriobotryae (Spain), Erwinia amylovora (Spain), Fusicladium eriobotryae [Spilocaea pyracanthae] (Spain), Glomerella cingulata (Japan), Pestalotia funerea [Pestalotiopsis funerea] (China and Japan), Phyllostica eriobotryae (China and Japan), and Pseudomonas eriobotryae [P. syringae pv. eriobotryae] (Japan) (Janick and Paull, 2008).

According to Orwa et al., (2009), the major pathogens of E. japonica are fireblight (Erwinia amylovora) and loquat scab (Fusicladium dendriticum var. eriobotryae [Venturia inaequalis]). In Florida (USA), the fungus Colletotrichum gloeosporioides [Glomerella cingulata] blights the flowers. In California, this species is most commonly attacked by the codling moth (Cydia pomonella), green apple aphid (Aphis pomi), scale (Aspidiotus perniciosus [Diaspidiotus perniciosus]) and wax scale (Ceroplastes floridensis).

In other countries, the fruits of E. japonica are attacked by the Mediterranean fruit fly (Ceratitis capitata), the Queensland fruit fly (Bactrocera tryoni) and the fungus Spilocaea eribotryae [Spilocaea pyracanthae]. In India, the anar caterpillar (Virachola isocrates [Deudorix isocrates]) bores into the fruit (Orwa et al., 2009). The roots of trees in India are preyed on by nematodes Mesocriconema xenoplax, Helicotylenchus spp., Hemicriconemoides communis, Haplolaimus spp. and Xiphinema insigne (Morton, 1987).

Eriobotrya japonica is widely planted as an ornamental tree and for its edible fruits. Loquat produces high levels of nectar with a heavy fragrance and has high honey potential. The fruit can be consumed fresh or processed and can be used for jam, juice, wine, syrup or as candied fruit, and the seeds are used to add an almond-like flavour to drinks and cakes (Hiep and Verheij, 1991). The seeds are rich in starch (20%) and have been used to make wine, and the juice can be used to prepare an alcoholic drink. In India and East Africa this species is commonly grown on the borders of the home compounds and lopped to provide fodder for goats and livestock (Hiep and Verheij, 1991; Orwa et al., 2009; PROTA, 2016). It is also planted as an ornamental tree, hedge tree and shade tree in gardens, highway medians, sidewalks and parks (Gilman et al., 2013). Its wood is pink, hard, close-grained and medium weight, and is highly prized by furniture makers. The wood of the tree is also used to make stringed musical instruments.

The leaves, flowers and fruits are commonly used in traditional Asian medicine, and there is evidence of pharmaceutically active compounds. The ether-soluble fraction of the ethanolic extract of the leaves showed anti-inflammatory activity when applied topically to rats. An alcoholic extract has been shown to exhibit anti-inflammatory and hypoglycaemic effects. For at least 40 years, Chinese food stores in the USA have sold a product imported from Hong Kong and recommended for chronic bronchitis, coughs and lung congestion. The contents are listed as loquat leaves along with other herbs (Janick and Paull, 2008). The flowers are used as insect repellent and, extracted in oil, in cosmetics (Hiep and Verheij, 1991).

Most major cultivars are derived from chance seedlings, but breeding programmes based on hybridization have been initiated. ‘Jiefangzhong’, bearing large fruit, has been a popular parent in China and is the parent of three cultivars. Cross-pollination is most successful with flowers of the second flush. Early and late flushes have abnormal stamens, very little viable pollen, and result in poor setting and undersized fruit. Breeders have released a whitish flesh cultivar, ‘Shiro Mogi’, which originated from an open-pollinated ‘Mogi’ seed irradiated with a 20 kR gamma-ray. Endosperm culture has been pursued in order to obtain triploids that might be seedless. Although plants with chromosome numbers close to triploid (2n = 45-50) were obtained from endosperm culture and from protoplasts, they did not survive (Janick and Paull, 2008). Seedless clones have been obtained from naturally occurring triploid seedlings derived from unreduced gametes and are under test. However, fruit size and fruit internal characteristics of these seedless clones show great variability, making them commercially unsuitable (Janick et al., 2015). The world’s largest collection of germplasm, more than 500 cultivars, is located in the National Fruit Germplasm Repository, Fuzhou, China.

Although there are more than 500 cultivars in China, only 50 are widely planted (Janick et al., 2015). Chinese cultivars can be divided into three groups: whitish flesh; north subtropical; and south subtropical with orange flesh. Most cultivars cultivated in Japan belong to the north subtropical group, but several cultivars, such as ‘Shiro Mogi’, could be placed in the whitish-flesh group. In China, widely planted cultivars had been classed as either ‘whitish flesh’ or ‘orange’, the former make up 30% of the number of total cultivars in China. Some whitish flesh cultivars, such as ‘Zhaozhong’ and ‘Baiyu’, are the leading cultivars in Jiangsu province. Among the orange cultivars, different ecological types have been formed in various zones during the long course of their cultivation and acclimatization. Ecotypes in China can be divided into two cultivar groups: the north subtropical cultivar group (NSCG) and the south subtropical cultivar group (SSCG). The NSCG is distributed in the mid- and north subtropical area, roughly in the provinces of the Yangtze River basin, 27-33°N where the average annual temperature is 15-18°C with low temperature of between -5°C and -12°C, and 800-1500 mm of annual rainfall. Snow and frost can occur. NSCG cultivars are characterized by cold resistance; most of their fruit are late ripening, small and high quality. Representative cultivars are ‘Dahongpao’ and ‘Luoyangqing’ in Zhejiang, ‘Baiyu’ and ‘Zhaozhong’ in Jiangsu, and ‘Guangrong’ in Anhui in China; these cultivars have been successfully introduced to the south subtropical zones and margins of tropical zones. The SSCG occurs in the margins of the tropical zone, approximately 19-27°N, with only a few days of frost and snow or temperature lower than 0°C, and more than 1500 mm annual rainfall. Cultivars of the SSCG have poor cold-resistance but are high yielding and early, while the fruit are large but flavourless. Representative cultivars include ‘Jiefangzhong’ in Fujian. Flowers and fruit are injured by cold when they are introduced to the north subtropical zones.

Cultivar variability manifests as fruit size, external and internal colour of skin, ease of peeling, flesh characters such as sweetness, acidity, texture, taste, seed number, keeping quality and disease resistance (Janick et al., 2015).

The following list of cultivars includes the country grown (in brackets) and their outstanding characteristics:

Principal sources: Janick and Paull (2008)

The rootstock generally is E. japonica itself, although E. deflexa and other species, even Photinia serrulata, have been used for rootstocks in China. Loquat seedlings are preferred over apple, pear, quince or pyracantha rootstocks under most conditions in Turkey. Quince and pyracantha may cause extreme dwarfing. Dwarfing on quince rootstocks has encouraged expansion of loquat cultivation in Israel since 1960. The growing of dwarf trees greatly reduces the labour needed for pruning, flower and fruit thinning, bagging and harvesting. Quince rootstock, which tolerates heavier and wetter soils, is widely used in Egypt. Nursery plants must be transplanted before the growth of spring buds, depending on climate. In China, leaves on the base of nursery plants are removed and the root system is often dipped in mud. Before planting, well-fermented manure is added to planting holes.

Principal sources: Janick and Paull (2008)

USDA National Nutrient Database for Standard Reference (USDA, 2016) report the approximate composition of 100 g of raw loquat fruit as: 86.73 g water, 0.43 g protein, 0.20 g total lipid (fat), 12.14 g carbohydrate (by difference), 1.7 g fibre (total dietary), and 70 kcal energy. Also reported are vitamin contents of 1.0 mg ascorbic acid, 0.019 mg thiamin, 0.024 mg riboflavin, 0.180 mg niacin, 0.100 mg vitamin B6, 14 µg folate, and 76 µg vitamin A. The mineral composition is 16 mg calcium, 0.28 mg iron, 13 mg magnesium, 27 mg phosphorus, 266 mg potassium, 1 mg sodium and 0.05 mg zinc.

In various cultivars, sucrose, sorbitol, glucose and fructose varied almost six-fold, but total sugars varied less than two-fold. Total soluble solid values can vary from 8 to 19% in different cultivars and under different conditions. Loquat flesh contains 0.42 g crude protein/100 g fresh weight, 146 mg essential and 387 mg total amino acids. Of 10 essential amino acids measured, leucine is the most abundant and cysteine-cystine the least abundant. Of 8 non-essential amino acids measured, glutamic and aspartic acids are the most abundant, with an unusually high level of proline (9.7 g/100 g recovered amino acids). The carotenoids of loquat fruit are mainly responsible for the flesh and skin colour, which varies from yellowish white, yellow to deep orange. Total carotenoid values, especially carotene, vary widely in flesh, fruit peel and pulp. In the peel, total carotenoid values are several times higher than in the pulp. The content of carotene in yellow-orange fruit is up to ten times higher than in the yellow-white fruit, while the contents of zeaxanthin, lutein and violaxanthin in yellow-orange fruit are much lower. In a methylene-chloride extract of a distilled fraction from loquat fruit, 18 volatile compounds were identified. The major components were phenylethyl alcohol, 3-hydroxy-2-butanone, phenylacetaldehyde and hexen-1-ols.

Principal sources: Janick and Paull (2008); Jackson et al. (2010)

China is the world's largest producer of loquat, with production reaching 1,200,000 t in 2010. Spain is the main exporting country, producing 50,000 t annually with approximately 70% exported. Other main producers include Turkey, India, Japan and Pakistan. In addition, Chile, Guatemala, Greece, Israel, Italy, Morocco and Portugal contribute to world production (Janick et al., 2015).