El-Hashash, EF; El-Absy, KM; ,
Barley (Hordeum vulgare L.) is one of the Neolithic founder crops of Old World agriculture. It is a flowering plant belonging to the family Poaceae or Gramineae (herbs) that is cultivated in temperate climates across the world at 350–4050 m above sea level, and evolved from H. spontaneum (K. Koch) Thell. The economically most important species of the genus is barley, H. vulgare. Species of barley consist of diploid (2n = 2x = 14), tetraploid (2n = 4x = 24), and hexaploid (2n = 6x = 42) cytotypes. Barley constitutes the fourth most important grain crop in the world after wheat, rice and maize. Barley grain is used as livestock feed and forage, malt beverages, human food, soil improvement and has medicinal value, but is barely considered as a highly-needed crop of the present era. Common barley hails originally from western Asia and North Africa. It is one of the earliest documented agricultural grains, dating back to the Neolithic period (8500 years ago) in the Nile Delta portion of the Fertile Crescent. Barley is a rich source of proteins, B vitamins, niacin, minerals and fiber dietary; also, it is a good source of manganese and phosphorus. Raw barley consists of carbohydrates (78%), proteins (10%), water (10%) and fat (1%). This chapter discusses the taxonomy, economic importance, origin and history, germplasm resources, traditional breeding methods and biotechnology methods, and their application for crop improvement in association with conventional breeding methods of barley.