Review on barley (Hordeum vulgare L.) improvement for drought stress tolerance in Ethiopia

Barley is very important food crop in the highlands of Ethiopia. Barley grain is important source of malt and food for human. In Ethiopia traditionally barley used for making of local food (injera), local bread (dabo), roasted grain(kolo), boiled grain (nifro), porridge(genfo) and other types of local beverages (beer). The byproducts are useful for livestock and poultry feed. Barely production significantly threatened by both biotic and abiotic stress. This study targeted to review on the abiotic factors of barley crop drought tolerance mechanisms, molecular bases of crop response and barely breeding strategies in moisture limited environment. Response and drought coping mechanisms in barley; re-establishment of cellular homeostasis, reduced stomatal density and correspondingly low stomatal conductance a higher level of abscisic acid, Dehydrins and osmotic adjustments. There are droughtassociated phenotypic traits and their interrelationships in barley, might be positive or negative. Some of the traits which are reliable indicators of drought tolerance; early flowering, root length, root density, root proliferation, root-shoot ratio and root penetration, root volume and root-shoot ratio etc. measurement of quantitative data of such root traits under field conditions is difficult, their indirect evaluation via related and easily measured traits can be helpful. Root traits, such as root length, root volume, and root dry weight; and shoot traits, such as plant height and shoot dry weight, are closely related mainly under low-moisture stress. The root traits are inversely related to plant height and shoot dry weight. Under moisture-stress conditions, plants allocate extra photosynthetic resources to roots. Grain number per spike, grain weight per spike, grain number per plant, grain weight per plant, and thousand-grain weight are pertinent traits often associated with low-moisture stress in barley. Nevertheless, a cultivar may be developed with multiple desirable traits by combining target alleles (QTL) obtained from various gene pools via introgression. However, it is less effective for traits associated with drought tolerance, which is influenced by multiple QTL and genetic interactions.