Flour from hard wheats (varieties evolved for the most part from T. aestivum) contains a high percentage of gluten and is used to make bread and fine cakes. The hardest-kerneled wheat is durum (T. durum); its flour is primarily used in the manufacture of macaroni, spaghetti, and other pasta products. White- and soft-wheat varieties are paler and have starchy kernels; their flour is preferred for piecrust, biscuits, and breakfast foods. Wheat is used in the manufacture of whiskey and beer, and the grain, the bran (the residue from milling), and the vegetative plant parts make valuable livestock feed. Before the introduction of corn into Europe, wheat was the principal source of starch for sizing paper and cloth.

Wheat is susceptible to many pests and diseases, the more destructive including rust, bunt (see smut), and the Hessian fly and chinch bug. All wheat-producing countries carry on breeding experiments to improve existing varieties or to obtain new ones with such dominant characteristics as disease resistance, increased hardiness under specific environments, and greater yield.

The great wheat-producing countries of the world are the United States, China, and Russia; extensive wheat growing is carried on also in India, W Europe, Canada, Argentina, and Australia. In the United States the wheat belt covers the Ohio Valley, the prairie states, and E Oregon and Washington; Kansas leads the states in production. Large-scale mechanized farming and continued planting of wheat without regard to crop rotation have exhausted the soil of large areas. High-yield wheat, one of the grains resulting from the Green Revolution, requires optimal growth conditions, e.g., adequate irrigation and high concentrations of fertilizer.

Wheat was one of the first of the grains domesticated by humans (see grain). Its cultivation began in the Neolithic period. Bread wheat is known to have been grown in the Nile valley by 5000 b.c., and its apparently later cultivation in other regions (e.g., the Indus and Euphrates valleys by 4000 b.c., China by 2500 b.c., and England by 2000 b.c.) indicate that it spread from Mediterranean centers of domestication. The civilizations of W Asia and of the European peoples have been largely based on wheat, while rice has been more important in E Asia. Since agriculture began, wheat has been the chief source of bread for Europe and the Middle East. It was introduced into Mexico by the Spaniards c.1520 and into Virginia by English colonists early in the 17th cent.

Wheat is classified in the division Magnoliophyta, class Liliopsida, order Cyperales, family Poaceae (Gramineae).