Barley(Hordeum vulgare L.) belongs to the order Poales, family Poaceae (Gramineae), genus Hordeum. Among 2010 and 2013, barley is the fifth most important worldwide crops in crop production after rice, maize, wheat, and soybean and the average per year over 134 million tons(FAO 2014).
Barley is a self-pollinating, short season crop, early mature and tolerant to saline, alkali soils and drought. It is more tolerant to alkaline soils but sensitive to acidic soils. soil PH between 6 and 8.5 is admissible to the growth of the plant. it is classified according to their growth habit as winter or spring cultivar. Most spring and winter cultivars require four to five days and temperature between 12 and 24?C to growth and development. Winter cultivars are planted in the fall season and mature in early summer and requires before flowering and complete their life cycle in the spring season to be exposed to the cold period (vernalization) (Stark 2003b). Spring cultivars are planted in the spring season and mature in mid-summer but these cultivars do not withstand frost temperature and require excess irrigation and less productivity than winter cultivars.
Barley is classified according to the number of spikelets as two-row barley (Hordeum vulgare L. distichum) and six-row barley (Hordeum vulgare L. hexastichum) (Badr et al., 2000; Kilian et al., 2006). The fertility of spikelets plays important role in determine row number of barley spike. Two-rowed genotype produces less grain per spike than six-rowed genotype. Two-rowed spikes have spikelets that are horizontally and sterile but six-rowed spikes have spikelets that are horizontally and fertile.
Barley also classified according to their hull adherence as hulless or naked (lemma and palea are separated from seed at maturity( and hulled barley)at maturity, palea and lemma stay attached to seed). Hulled barley has the hull that protects embryo during and after harvesting from destruction and has the characteristic of higher yielding and it is used to feed the animal. But, hulless (naked) barley used directly as a food for human. The great majority of the cultivated barley called hulled barley whereas the remaining genotypes called naked or hulless barley 34.
History and distribution
Barley has been cultivated mainly for food, since ancient times. It was domesticated from wild species Hordeum spontaneum about 10000 years ago. The initiation of barley is from Iberian peninsula and extend to southwestern, eastern, southern Asia and North Africa 10.
Barley has been cultivated as a food source in Asia mainly in Japan, Korea, India and in North Africa, Middle East, eastern and northern Europe mainly in England, Germany, Russia, Ethiopia, Morocco, and Poland but now it is cultivated for all tropical and non-tropical countries13.
Uses and properties
Barley is produced for many uses, where 60-70% of the production is used for animal feed, 30-40% of the production is used in malting to make alcoholic beverage like whiskey and beer, and only 2-4% for human food (Newman and Newman 2008).
Barley is used as medicinal uses such as lowering of blood sugar and pressure, lowering cholesterol, treating boils of skin and promoting weight loss 26. Also, barley can be used as a food or chemical industry through the production of starch 4. It is used as animal feed and as straw for bedding in both developed and developing countries. It can be added to bread, cakes, biscuits as a foodstuffs 1.it is used for adult monogastrics and ruminants feeding. Wheat and barley grains are used commonly in the feeding of pig and poultry in the majority of European countries (Bergh et al., 1999).
There are several factors that affect on chemical constituents, bioavailable energy content and nutritive value, these include environmental factors, genetic factors, and interaction between two factors(Zhan et al., 1994; Valaja et al., 1997; Andersson et al., 1999).
The main barley components are starch, which constitutes 60% of dry matter, dietary fiber (both soluble and insoluble) 20% of dry matter and crude protein 12% of dry matter (Åman and Newman, 1986; Oscarsson et al., 1996).
Barley grain contains phenolic compounds, phytic acid, lignin that connected with good health 18, 19. Also, It contains vitamin B-complex, minerals, vitamin E. it rich in selenium, iron, magnesium, zinc, copper12.