2. Barley (Hordeum vulgare L.)
Barley (Hordeum vulgare L.) is one of the founder crops of old
World agriculture.
One of the first cultivated grains (Eurassia) around10,000 years
ago.
It’s the 4th largest grain produced in the world after maize, rice
and wheat.
Barley can be turned into breads and porridges, as well as beers
and whiskies.
In recent times, 55% – 60% of the barley crop has been used for
feed, 30% – 40% for malt (brewary), 2% – 3% for food, and 5% for
seed.
4. Crop Botany
Family: Gramineae
Subfamily: Festucoideae
Tribe: Hordeae and the Genus: Hordeum
Self pollinating
Cultivated barleys belong to the subspecies vulgare
Wild forms of barley belong to the subspecies spontaneum
Basic chromosome number (x) of Hordeum is 7
All cultivated barleys are diploid annuals (2n = 14)
Barley is arguably the most widely adapted cereal grain
species with good drought, cold, and salt tolerance.
5. Plant morphology
The ligule, and especially the auricles, distinguish barley from other cereal grains: they are
glabrous, envelop the stem and can be pigment with anthocyanins.
Growth type: Annual, cool season bunch grass, 2-4 ft tall
Morphology: Stems are hollow and jointed, leaf margins and surfaces are smooth and
tapered
7. The spike or head of barley consists of a series of spikelets that
are attached – in sets of three – at nodes to alternating sides of
the rachis. Each spikelet contains a floret.
There are three florets at each node, and in two-rowed barley
only the central floret is fertile, whereas in six-rowed all florets
are fertile
Three anthers per floret and highly self pollinated
Spike anatomy and morphology
13. Origin and diversity
Exact origin of barley is still debatable
But archeological evidence points that its around fertile crescent (Iran, Iraq, Israel, palestine)
15. Wild barley, Hordeum spontaneum C. Koch,
is the progenitor of cultivated
barley, Hordeum vulgare L.
Important staple crops in old world
Neolithic agriculture
The centre of origin of barley has not been
fully resolved.
H. spontaneum, the wild ancestor of
cultivated barley, has been discovered in
several geographically distinct locations
other than the Fertile Crescent, such as
Morocco, Algeria, Libya, Egypt, Crete,
Ethiopia, and Tibet, leading to the proposal
of a multicentric origin for this crop
Origin and domestication
Hordeum spontaneum (Wild barley)
16. Traits selection and domestication
Earliest domestication traits: Shattering resistant (tough rachis rather brittle rachis), increase
to six-row and the development of free-threshing (or naked) barley
Fuller and Alison, 2014
17. Spontaneum Vulgare
Shattering (brittle rachis) Shattering resistant (non-brittle rachis)
2-row 2-row, 6-row
Adhering hulls Adhering, non-adhering (naked)
Winter annual Winter, facultative, and spring annual
Domestication traits
Wild barley has a brittle spike; upon maturity, the spikelets
separate, facilitating seed dispersal.
Domesticated barley has non-shattering spikes, making it much
easier to harvest the mature ears.
The non-shattering condition: mutation in one of two tightly linked
genes known as Btr1 and Btr2;
Many cultivars possess both mutations. The non-shattering
condition is recessive, so varieties of barley that exhibit this
condition are homozygous for the mutant allele.
18. How domestication happened?
1. Shattering to Non shattering
Wild barley spikes are brittle at
maturity due to thin cell walls at rachis
nodes
This characteristic evolved by
duplication and neo-functionalization
of two genes, Btr1 and Btr2
During domestication, deletions in Btr1
or Btr2 converted the rachis to non-
brittle
The deletions happened twice: first in
the South (btr1) and then in the North
Levant (btr2)
Neo-functionalization is the process by
which a gene acquires a new function
after a gene duplication event.
*Levant is eastern Mediterranean area
Pourkheirandish et al., 2015
19. Two row vs six row barley
Spikelets are arranged in triplets which alternate along the rachis.
Two row barley: In wild barley, only the central spikelet is fertile, while the
other two are reduced (rudimentary)
Six row barley: A pair of mutations (one dominant, the other recessive)
result in fertile lateral spikelets to produce six-row barleys.
21. 2. Two row to six row
Evolutionary benefit of two row barley for plant : advantageous for seed
dispersal after shattering (as lateral spikelet's are rudimentary, may stick to
animals fur).
vrs1 (six-rowedspike 1), the gene responsible for the six-rowed spike in barley
Vrs1 allele (for two-rowed barley)
vrs1 (6 rowed barley)
(loss of function)
Domesticated barley
Mutation
or
Natural sports
VRS1 protein suppresses development
of the lateral rows.
Loss of function of Vrs1 resulted in
complete conversion of the
rudimentary lateral spikelets in two
rowed barley into fully developed
fertile spikelets in the six-rowed
phenotype.
23. (A) Mature caryopses of covered (left two) and naked (right two), (B) Part of a mature spike of covered
(Left) and naked (Right) barley
In contrast to other cereals, typical barley cultivars have caryopses
with adhering hulls at maturity, known as covered (hulled) barley.
However, a few barley cultivars are a free-threshing variant called
naked (hulless) barley.
Covered (Hulled) vs Naked barley
24. The wild progenitor of barley, H. vulgare subsp. spontaneum, has
covered grains.
The covered/naked caryopsis in barley is controlled by a single locus
(nud, for nudum)
the covered caryopsis allele (Nud) is dominant over the naked one
(nud).
3. Hulled to naked barley
Nud allele (covered, wild barley)
Mutation
or
Natural sports
nud (naked barley)
(loss of function)
Domesticated barley
Evolutionary advantage of hulled barley in wild:
The covered grain is therefore considered adaptive
in the wild: the hulls protect the caryopses from
various biotic and abiotic stresses, and the awn
attached to the distal end of the lemma facilitates
seed dispersal and burial
25. 4. Growth habit
Domesticated barley can be grown in Winter, facultative, and spring annual
Wild barley was only grown in winter
These genes, two dominant (VRN1 and VRN3) and one recessive (vrn2), are
responsible for spring growth habit, whereas only the haplotype combining
their allelic genes (vrn1, VRN2 and vrn3) exhibits winter growth habit
Significance: Acquisition of spring growth habit is thought to be one of the
driving forces for the expansion of the cultivable area for wheat and barley
(von Bothmer et al. 2003).
winter, facultative and spring
26. In spring or vernalized winter barley, (Long days) LDs strongly
promote flowering, whereas short days (SDs) delay reproductive
development (Monteagudoet al.,2019).
Flowering under LDs photoperiod response is under major control of
the Photoperiod-H1(Ppd-H1) gene (Turneret al.,2005; Campoliet
al.,2012).
Under SDs condition,Photoperiod-H2(Ppd-H2) is described as a
promoter of flowering.
The mutant allele ppd-H1exhibits reduced photoperiod
responsiveness and is highly advantageous in spring barley
5. Photoperiod sensitivity (Circadian clock)
28. A crop wild relative (CWR) is a wild plant closely related to
a domesticated plant. It may be a wild ancestor of the
domesticated (cultivated) plant, or another closely related taxon.
Wild Hordeum species are distributed through Europe, Asia, Africa
and the Americas. Secondary centers of diversity of cultivated
barley are found in Ethiopia and Morocco and parts of Asia.
Cultivated barley (Hordeum vulgare ssp. vulgare) and its
progenitor known as ‘wild barley’ (H. vulgare ssp. spontaneum,
hereafter HSP) are two subspecies of H. vulgare, a diploid species
with seven chromosome pairs (2n = 2x = 14) (Brown et al., 1978).
Crop Wild relatives of Barley
31. Other wild barley species of genus Hordeum, which form the secondary
and tertiary gene pool of barley, are diploid (2n = 2x = 14), autotetraploid
(2n = 4x = 28) and autohexaploid (2n = 6x = 42) grass species.
The natural distribution of wild species of barley ranges from the
Mediterranean portion of the Middle East, across the Zagros Mountains
(Iran), and into adjacent Southwest Asia (Morrell and Clegg, 2011).
From the wild species of genus Hordeum, H. murinum and H. marinum
are more abundant in Iran and are known as typical weeds in the farms.
Many of the wild Hordeum species including H. bogdanii, H. secalinum,
H. depressum, H. patagonicum, H. bulbosum, H. euclaston, H. pusillum
and H. arizonicum were found in drought and salt-affected dryland
habitats, and therefore could be a useful source of tolerance to salt and
drought stress (Mano and Takeda, 1998)
Other wild barley species of genus Hordeum
36. • Heading Date
• Days to Maturity
• Lodging
• Disease Resistance
• Yield
• Grain Pumpness
• Grain Protein
• Straw stiffness and forage quality
Production Traits
Grain plumpness, which is the percentage weight of grains retained over a 2.5mm sieve (%
w/w).
Grain plumpness and grain weight are important traits routinely tested by barley breeding
and germplasm enhancement programs to ensure that new varieties have inherently good
grain size and homogeneity.
37. • Plumped kernels has high starch and very desirable to brewery process
• High protein can lead to haze problems in the beer and it is more difficult for
maltsters to control the color of the malt during processing. Beer color is
derived from the malt
Importance of Grain Plumpness and grain protein in malting extract
Malting process
Plumpness and protein content effect
the
Speed of steeping process in malting.
Thin grain will absorb water and modify
at a faster rate than plump grain.
Protein also affects the rate of water
uptake and speed of modification.
38. Quality Traits
• Malt extract
• Wort protein
• S/T protein
• Diastatic power
• Alpha amylase
• FAN
• Beta-glucan
• Wort Viscosity
39. Wort Protein: Wort is the liquid extracted from the mashing process
during the brewing of beer or whisky. Wort contains the sugars, the most
important being maltose and maltotriose, that will be fermented by
the brewing yesat to produce alcohol.
• Wort also contains crucial amino acids to provide nitrogen to the yeast as
well as more complex proteins contributing to beer head retention and
flavour.
The Kolbach index is a ratio of soluble wort protein to the total malt
protein expressed as a percentage (often noted as S/T)
Normal values for base malt between 42 - 46% • Higher for some
specialty malts 45 - 52% • Lower for classic pilsner malts 39 - 42%
40. Diastatic power (DP) refers to the enzymatic power of the malt
itself. Its ability to break down starches into even simpler
fermentable sugars during the mashing process.
• The term “diastatic” refers to “diastase” enzymes. There are two
“diastese” enzymes, the first is alpha amylase and the second is
beta amylase
• For most craft brewers, DP >115 will provide sufficient enzymes to
process the mash.
Alpha amylase (AA) : Barley does not contain alpha amylase (glucan
1,4-glucanohydrolase), but this enzyme develops in the grain during
malting . Copious quantities of alpha amylase are synthesized in the
aleurone layer that surrounds the endosperm.
For most brewers with normal levels of un-malted grains or
adjuncts, >50 AA is more than enough for breakdown of starch into
simple sugars
41. Free Amino Nitrogen (FAN) is defined as the sum of the individual
amino acids, ammonium ions, and small peptides (di- and
tripeptides) in wort.
• Some brewing scientists regard FAN as a better index for the
prediction of healthy yeast growth, viability, vitality, fermentation
efficiency, and hence beer quality and stability.
Insufficient FAN (<150mg/L)
• Poor yeast growth
• Slow or incomplete fermentations
Excess FAN (>250 mg/L)
• Utilized by other micro-organisms and converted
into negative flavor compounds
• Contributes to increased color formation during
wort boil
42. The measured wort viscosity gives information on:
• Comparability of malt from brew to brew
• Information on processability of the wort
• Breakdown of cell materials during mashing
• Degree of modification to fermentable sugars
• Filterability
• Foam stability
• Higher viscosity values show insufficient cell wall
decomposition that can cause difficulties in wort and
beer filtration. Lower values show too low break down
of the cell wall material causing poor foam stability and
poor taste of the beer.
50. Speed breeding for multiple disease resistance in barley
Yellow indicate that plants were grown under accelerated growth conditions
and not subject to phenotypic screening
Prof. Lee T. Hickey
Speed breeder
Hickey et al., 2017
