polyploid

In genetics, possessing three or more sets of chromosomes in cases where the normal complement is two sets (diploid). Polyploidy arises spontaneously and is common in plants (mainly among flowering plants), but rare in animals. Many crop plants are natural polyploids, including wheat, which has four sets of chromosomes per cell (durum wheat) or six sets (common wheat).

Plant breeders can induce the formation of polyploids by treatment with a chemical, colchicine.

Matings between polyploid individuals and normal diploid ones are invariably sterile. Hence, an individual that develops polyploidy through a genetic aberration can initially only reproduce vegetatively, by parthenogenesis, or by self-fertilization (modes of reproduction that are common only among plants). Once a polyploid population is established, however, the members can reproduce sexually.