Wheat

I

Introduction

Wheat, common name for cereal grasses of a genus of the grass family, cultivated for food, such as bread, since prehistoric times by the peoples of the temperate zones and now the most important grain crop of those regions (see Agriculture).

Wheat is a tall, annual plant attaining an average height of 1.2 m (4 ft). The leaves, which resemble those of other grasses, appear early and are followed by slender stalks terminating in spikes, or so-called ears, of grain.

II

Uses

The main use of wheat is in the manufacture of flour for bread and cakes. In general, hard varieties are used for bread flour and pasta, and soft varieties for cake flour. Wheat is used also in the production of breakfast foods and to a limited extent in the making of beer, whisky, and industrial alcohol. Low grades of wheat, and by-products of the flour-milling, brewing, and distilling industries, are used as feed for livestock. A minor amount of wheat is used as a coffee substitute, and wheat starch is employed as a sizing for textile fabrics.

III

Classification

Species of wheat are classified according to the number of chromosomes found in the vegetative cell. They are divided into three series: the diploid, or einkorn, containing 14 chromosomes; the tetraploid, or emmer, containing 28 chromosomes; and the hexaploid, or bread wheat, containing 42 chromosomes. Wheat species cross-breed relatively frequently in nature. Selection of the best varieties for domestication took place over many centuries in many regions. Today, the varieties of common, club, and durum wheats are of the most importance commercially, but other species are still grown to suit local conditions, and they provide essential stock for systematic plant breeding programmes.

IV

Varieties

According to the regions in which they are grown, certain types of wheat are chosen for their adaptability to altitude, climate, and yield. The common wheats grown in northern Europe, Russia, the United States, and Canada are spring and winter wheats, planted either in the spring for summer harvest or in autumn for spring harvest. The colour of the grain varies from one type to another; white wheats are mostly winter wheats, red are spring wheats. Closely related to the common wheats are the club wheats, which have especially compact spikes, and spelta, in which the glumes (reduced, scale-like bracts) tightly enclose the grains. Durum wheat (Latin, durum, “hard”) is so called because of the hardness of the grain. It is grown in the Mediterranean region for making pasta and has a very high gluten content. New high-yielding wheats were developed in the 1960s for use in developing countries, and research on them continued in the 1970s. Experimental programmes have produced commercial wheat varieties for hardiness and disease resistance. In 1978 the identification of a drought-resistant, high-protein, ancestral species growing in the Middle East held promise of still more highly improved wheat varieties.