Wheat Triticum spp
Wheat is by far the most important food grain of temperate regions. Its role in human subsistence is matched by the deep significance of wheat in religion and daily life. Wheat, in the form of bread, is central to Jewish and Christian rites. Although barley was domesticated at the same time, has higher yields, and was the most important cereal in antiquity, wheat has always been more highly valued, probably because of its better taste and more versatile culinary properties.
Papago winnowing wheat, ca.1907. Library of Congress, Prints & Photographs Division, Edward S. Curtis Collection.
The wheats divide into two groups, hulled and free-threshing. On threshing, the ear (spike) of hulled wheats breaks up into individual spikelets, in each of which one to three grains are tightly enclosed by tough husks or hulls (glumes). Before the grains can be consumed, they must be dehu-sked, traditionally by pounding in a mortar. In contrast, the glumes of free-threshing wheats are light and break away during threshing, releasing the naked grains immediately. Most wheats cultivated today are free-threshing; all wild wheats and many species cultivated in the past were hulled.
The earliest cultivated wheats were hulled forms. Einkorn wheat (T. monococcum) and emmer (T. dicoccum) were domesticated from wild einkorn (T. boeoticum) and wild emmer (T. dicoccoides) respectively, in the Fertile Crescent of the Near East. The earliest securely dated finds of domesticated einkorn and emmer are at Neolithic (Pre-Pottery Neolithic B) sites in Syria, Jordan, and southeast Turkey, dating from 9500 to 9200 14C years ago. Genetic evidence suggests that present-day einkorn and emmer derive from one or two domestications, probably in southeast Turkey. Emmer was the main wheat species grown by early farmers in Europe and the Near East and the only wheat grown in ancient Egypt, where emmer bread and beer were staple foods. Einkorn has always been less important. Because of their ability to thrive on poor soils and to resist fungal diseases, emmer and einkorn are still grown in wet mountainous areas stretching from the Pontic mountains of Turkey to the Carpathian mountains of eastern Europe, and in Italy and Spain. In Italy emmer is known as farro and cooked whole with beans or tomatoes to make soup. Einkorn is used as animal feed and for thatching, and in Turkey is favored as a food grain for cracked wheat (bulgur). Unlike emmer and spelt, einkorn has not become a popular health food, and it is in danger of becoming extinct as a crop.
Macaroni wheat (T. durum) is the free-threshing form of emmer wheat, with hard, flinty grains. It first appeared in the Near East about 9000 14C years ago. Macaroni wheat has always been important in Mediterranean areas. Its best-known use is for pasta, a food of uncertain origin, perhaps from the Arab world and not, as often claimed, brought back from China by Marco Polo. In the 19th century the Ukraine became the leading exporter of macaroni wheat for pasta making, but it lost this position to the United States during World War I. Macaroni wheat also makes a delicious bread that is a staple food in Sicily. Rivet wheat (T. turgidum) is a closely related species that is well adapted to the cooler conditions of northern Europe. It was popular during the medieval period, but bread wheats proved better adapted to the threshing machines introduced in the 19th century, and were better suited to industrialized baking. Rivet wheat has notably soft, floury grains, and produced a good bread-making flour that was mixed with flour from rye and bread wheat for daily baking. Miracle wheat (T. turgidum var. pseudocervinum) is a form of rivet wheat with branched ears, first recorded by the Roman author Pliny some 2000 years ago. Extravagant claims are often made for its yield but, sadly, miracle wheat has yields of grain well below those of ordinary wheats. It is often claimed that miracle wheat or mummy wheat derives from grains found in ancient tombs and subsequently germinated. However, except when stored at very low temperatures, cereal grains lose their ability to germinate within a few years or, at best, decades.
Spelt (T spelta) is a hulled wheat that became widely cultivated much later than most other wheats. Genetic evidence shows that it is the result of the hybridization of emmer wheat and a wild goatgrass, Aegilops tauschii, some 8000 14C years ago near the Caspian Sea. However, spelt never became part of the Near Eastern crop complex that spread to Europe through the Balkans. Instead, it suddenly appears as an important crop in central Europe about 4000 years ago. Spelt displaced emmer as the major wheat of antiquity in Europe, before being displaced in turn by free-threshing wheat. Spelt has continued in local cultivation in Germany and Switzerland, where it is much appreciated for use in baking bread known as Dinkelbrot. Spelt grains are widely sold in health food shops in Europe and North America, and cultivation in western Europe continues to expand.
Spelt is often and mistakenly thought to have been grown in Pharaonic Egypt or the ancient Near East; this error results from confusion with emmer wheat, which was widely grown in both areas in antiquity.
Bread wheat (T. aestivum) is free-threshing and closely related to spelt. As with spelt, genes contributed from goatgrass (Aegilops) give bread wheat greater cold hardiness than most wheats, and it is cultivated throughout the world's temperate regions. Bread wheat is by far the most important wheat species today. Wheat first reached North America with Spanish missions in the 16th century, but North America's role as a major exporter of grain dates from the colonization of the prairies in the 1870s. As grain exports from Russia ceased in the First World War, grain production in Kansas doubled. Worldwide, bread wheat has proved well adapted to modern industrial baking, and has displaced many of the other wheat, barley, and rye species that were once commonly used for bread making, particularly in Europe. Compact wheats (T compactum, in India T. sphaerococcum) are closely related, but have a much more compact ear, with spikelets packed closer together.
Modern wheat varieties have short stems, the result of RHt dwarfing genes that reduce the plant's sensitivity to gibberellic acid, a plant hormone that lengthens cells. RHt genes were introduced to modern wheat varieties in the 1960s from Norin cultivars of wheat grown in Japan. Short stems are important because the application of high levels of chemical fertilizers would otherwise cause the stems to grow too high, resulting in lodging (collapse of the stems). Stem heights are also even, important for modern harvesting techniques.
See: Origins and Spread of Agriculture, pp. 16 and 17
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