Published online by Cambridge University Press: 22 September 2009
Barley is a cool-season crop in countries with a Mediterranean climate and is well adapted to stressful and extreme environments. Barley fields can be seen as high as 4800 m asl in the Himalayas, in latitudes over 60°N in Iceland and Scandinavia and in the rain-fed semi-arid regions of WANA with less than 250 mm annual rainfall. Barley is a principal food crop in highlands and marginal areas where other cereals will not grow, as well as animal feed and forage all over the world. It is also an important industrial crop, providing raw material for malt and beer production. Its straw is of better quality than that of wheat and is, therefore, a valuable complement of cattle and small ruminant diets. Barley is grown in a wide range of environments but nearly two-thirds of the world's production is grown in subhumid or semi-arid regions.
BOTANY AND DISTRIBUTION
Barley belongs to the tribe Triticeae of the grass family Poaceae together with other important cereals, wheat and rye. The main distinction from other members of the tribe is that each spike node bears three 1-flowered spikelets (‘triplets’) of which one, two or all three are fertile. The genus Hordeum includes about 30 species (Bothmer 1992a). According to the same author, the 45 taxa of the genus are mostly diploid (2n=2x=14 chromosomes, 28 taxa), but also tetraploid (2n=4x=28 chromosomes, 16 taxa) and hexaploid (2n=6x=42 chromosomes, 8 taxa) with a basic chromosome number x=7.