http://rationalrevolution.net/images/cabageraddish.jpg In 1928, the Russian plant geneticist Karpechenko produced a new species by crossing a cabbage with a radish. Although belonging to different genera (Brassica and Raphanus respectively), both parents have a diploid number of 18. Fusion of their respective gametes (n=9) produced mostly infertile hybrids.

However, a few fertile plants were formed, probably by the spontaneous doubling of the chromosome number in somatic cells that went on to form gametes (by meiosis). Thus these contained 18 chromosomes — a complete set of both cabbage (n=9) and radish (n=9) chromosomes.

Fusion of these gametes produced vigorous, fully-fertile, polyploid plants with 36 chromosomes. (Unfortunately, they had the roots of the cabbage and the leaves of the radish.)

These plants could breed with each other but not with either the cabbage or radish ancestors, so Karpechenko had produced a new species.