Barley
Barley is a cereal grain derived from the annual grass Hordeum vulgare. It serves as a major animal feed crop, with smaller amounts used for malting (in beer and whisky) and in health food. In 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 km²).
Etymology
The Oxford English Dictionary records the derivation from the Old English bærlic “barley”, although the -lic ending may indicate it was an adjective pertaining to the crop or plant, rather than a noun. It was first recorded around 966 CE in the compound word bærlic-croft. The old English word was bære, which was related to the Latin word farina “flour”, and gave rise to bærlic meaning “of barley”. It survives in the north of Scotland as bere, and refers to a specific strain of six-row barley grown there. The word barn, which originally meant barley-house, is also rooted in these words.
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 and is abundant in disturbed habitats, roadsides and orchards. Outside of this region the wild barley is less common and is usually found in disturbed habitats.
Domestication
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 is caused by a mutation in one of two tightly linked genes known as Bt1 and Bt2; 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.
Two row and six row barley
Spikelets are arranged in triplets which alternate along the rachis. In wild barley (and other Old World species or 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. This produces six-row barleys. (See Cultivars). Recent genetic studies have revealed a mutation in one gene, vrs1 is responsible for the transition from two-row to six-row barle.
Hulled and naked 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 in order to increase the digestible energy of the grain, especially for swine and poultry. 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.
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 C.Koch. Two-rowed barley with non-shattering spikes is classified as H. distichum L., six-rowed barley with non-shattering spikes as H. vulgare L. (or H. hexastichum L.), and six-rowed with shattering spikes as H. agriocrithon Åberg. The fact that these differences were driven by single-gene mutations, coupled with cytological and molecular evidence, has led most recent classifications to treat these forms as a single species, H. vulgare L.
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