Barley (Hordeum vulgare L.), a member of the grass family, is a major cereal grain. It was one of the first cultivated grains and is now grown
widely. Barley grain is a staple in Tibetan cuisine and was eaten widely by peasants in Medieval
Europe.
Detailed description
as animal fodder, as a
source of fermentable material for beer and certain distilled beverages, and as a component of various health
foods. It is used in soups and stews, and in barley
bread of
various cultures. Barley grains are commonly made into malt in a traditional and ancient method of
preparation.
In a 2007 ranking of cereal
crops in the world, barley was fourth both in terms of quantity produced (136
million tons) and in area of cultivation (566,000 square kilometres or 219,000
square miles).[2]
Etymology
The Old
English word
for 'barley' was bære,
which traces back to Proto-Indo-European and is cognate to the Latin word farina "flour". The direct ancestor
of modern English "barley" in Old English was the derived adjective bærlic, meaning "of barley".[3] The first citation of the form bærlic in the Oxford English Dictionary dates to around 966 CE, in the compound
word bærlic-croft.[4] The underived word bære survives in the north of Scotland as bere, and refers to a specific strain of six-row
barley grown there.[5] The word barn, which
originally meant "barley-house", is also rooted in these words.[3]
Biology
Barley is a member of the grass
family. It is a self-pollinating, diploid species with 14 chromosomes. The
wild ancestor of domesticated barley, Hordeum
vulgare subsp. spontaneum, is abundant in
grasslands and woodlands throughout the Fertile
Crescent area of
Western Asia and northeast Africa, and is abundant in disturbed habitats, roadsides and orchards.
Outside this region, the wild barley is less common and is usually found in
disturbed habitats.[6] However, in a study of genome-wide
diversity markers, Tibet was found to be an additional center of
domestication of cultivated barley.[7]
Domestication
Wild barley has a brittle spike; upon maturity,
the spikelets separate,
facilitating seed
dispersal. Domesticated barley has nonshatteringspikes,
making it much easier to harvest the mature ears.[6] The nonshattering condition is caused by a mutation in one of two tightly linkedgenes
known as Bt1 and Bt2;
many cultivars possess both mutations. The nonshattering
condition is recessive, so varieties
of barley that exhibit this condition are homozygous for the mutant allele.[6][clarification needed]
Two-row and six-row barley
Spikelets are arranged in
triplets which alternate along the rachis. In
wild barley (and other Old World species of Hordeum), only the central
spikelet is fertile, while the other two are reduced. This condition is
retained in certain cultivars known as two-row barleys. A pair of mutations
(one dominant, the other recessive) result in fertile lateral spikelets to
produce six-row barleys.[6] Recent genetic studies have revealed that a
mutation in one gene, vrs1,
is responsible for the transition from two-row to six-row barley.[8]
Two-row barley has a lower
protein content than six-row barley, thus a more fermentable sugar content.
High-protein barley is best suited for animal feed.
Malting barley is usually lower protein[9] ("low grain nitrogen", usually
produced without a late fertilizer application) which shows more uniform
germination, needs shorter steeping, and has less protein in the extract that
can make beer cloudy. Two-row barley is traditionally used in English ale-style
beers. Six-row barley is common in some American lager-style
beers, especially when adjuncts such as corn and rice are used, whereas
two-row malted summer barley is preferred for traditional German
beers.
Hulless barley
Hulless or "naked"
barley (Hordeum vulgare L.
var. nudum Hook. f.) is a form of domesticated
barley with an easier-to-remove hull. Naked
barley is an ancient food crop, but a new industry has developed around uses of
selected hulless barley to increase the digestible energy of the grain,
especially for swine and poultry.[10] Hulless barley has been investigated for
several potential new applications as whole grain, and for its value-added
products. These include bran and flour for multiple food applications.[11]
Classification
In traditional classifications
of barley, these morphological differences have led to different forms of
barley being classified as different species. Under these classifications, two-rowed
barley with shattering spikes (wild barley) is classified as Hordeum spontaneum K. Koch. Two-rowed barley with nonshattering
spikes is classified as H. distichum L.,
six-row barley with nonshattering spikes as H.
vulgare L. (or H. hexastichum L.),
and six-row with shattering spikes as H.
agriocrithon Åberg.
Because these differences were
driven by single-gene mutations, coupled with cytological and molecular evidence, most recent classifications treat
these forms as a single species, H.
vulgare L.
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