The hybrids between these are sterile but, after chromosome doubling, the allotetraploids, B. juncea, B. carinata and B. napus are fertile. The cytogenetic interrelationships among six Brassica species and Raphanus sativus . Intergeneric crosses between R. sativus and other Brassica species are also possible.
Cytoplasmic genome is designated by capitals.
Present day varieties B. rapa and B. oleracea include many familiar and not so familiar vegetables which are represented in the lab today. Oil-seed rape and canola are forms of B. napus . The rapid cycling B. rapa which we have used in several labs was obtained by selection and breeding from a worldwide collection of 2000 forms held by the United States Department of Agriculture.