Consequently, the duplicated chromosomes fail to separate in mitosis. Onion cells exposed to colchicine for several days may have over 1000 chromosomes inside. These are sterile because they cannot form gametes with a balanced assortment of chromosomes. However, the tetraploid plants can breed with each other. So in one generation, a new species has been formed.
Polyploidy even allows the formation of new species derived from different ancestors.
In 1928, the Russian plant geneticist Karpechenko produced a new species by crossing a cabbage with a radish. Fusion of these gametes produced vigorous, fully-fertile, polyploid plants with 36 chromosomes. These plants could breed with each other but not with either the cabbage or radish ancestors, so Karpechenko had produced a new species. The process also occurs in nature. Modern wheat and perhaps some of the other plants listed in the table above have probably evolved in a similar way.