II.

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, containing 42 chromosomes. Wheat species crossbreed relatively frequently in nature. Selection of the best varieties for domestication took place over many centuries in many regions. Today, only varieties of common, club, and durum wheats are of commercial importance, but other species are still grown to suit local conditions, and they provide essential stock for formal breeding programs (see Plant Breeding).