WHEAT

Wheat (Triticum spp.) is a worldwide cultivated grass from the Fertile Crescent region of the Near East. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize (784 million tons) and rice (651 million tons). Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, breakfast cereal, pasta, juice, noodles and couscous; and for fermentation to make beer, alcohol, vodka or biofuel. Wheat is planted to a limited extent as a forage crop for livestock, and the straw can be used as fodder for livestock or as a construction material for roofing thatch. Although wheat supplies much of the world's dietary protein and food supply, as many as one in every 100 to 200 people has Celiac disease, a condition which results from an immune system response to a protein found in wheat: gluten (based on figures for the United States).

Wheat originated in the area known as the Fertile Crescent in Western Asia. The genetic relationships between wild and domesticated populations of both einkorn and emmer wheat indicate that the most likely site of domestication is near Diyarbakır in Turkey. Wild wheats were domesticated as part of the origins of agriculture in the Fertile Crescent. Cultivation and repeated harvesting and sowing of the grains of wild grasses led to the domestication of wheat through selection of mutant forms with tough ears that remained intact during harvesting, larger grains, and a tendency for the spikelets to stay on the stalk until harvested. Because of the loss of seed dispersal mechanisms, domesticated wheats have limited capacity to propagate in the wild

The exact timing of the first appearance of domesticated wheats is currently uncertain, but is either in the PPNA period (9800-8800 cal BC) or the early-mid PPNB (8800-7500 cal BC). Domesticated einkorn and emmer wheat has been identified at three PPNA sites in the northern Levant, Iraq ed-Dubb, Jericho and Tell Aswad, but both the dating and the domesticated status of these cereals is disputed Domesticated wheats (and other Neolithic founder crops) are unambiguously present at early-mid PPNB sites in the northern Levant, such as Ain Ghazal, Abu Hureyra and Tell Aswad, and in southeast Turkey at Cafer Höyük and Çayönü. As a round figure, it is correct to say that wheats have been domesticated for about 10,000 years.

The cultivation of wheat began to spread beyond the Fertile Crescent during the Neolithic period, reaching the Aegean by 8500 cal BC and the Indian subcontinent by 6000 cal BC. By 5,000 years ago, wheat had reached Ethiopia, Great Britain, Ireland and Spain. A millennium later it reached China Claims have been made for independent domestication of wheat outside the fertile crescent, but these lack evidence of the presence of wild wheats or of early domesticated wheat