Trait inheritance, fertility, and genomic relationships of some n = 9 Brassica species

Karyotypic differences among n = 9 Brassica species, as well as the inheritance of some morphological characteristics, are reported. Annual habit, anthocyanin pigmentation in leaf and stem, enlarged stem, glossy foliage, dark green foliage, white flower and leaf pubescence were all expressed as dominant characteristics and in most cases were determined by one or two genes. 172 intra- and interspecific hybrids of the species belonging to the Brassica oleracea cytodeme were analyzed for fertility and meiotic chromosome behavior. B. alboglabra, B. bourgeaui, B. cretica spp. cretica, B. montana and B. oleracea produced fertile interspecific hybrids, indicating that geographical isolation is the only barrier to gene exchange. Interspecific hybrids generated from crosses of B. incana, B. insularis and B. rupestris to other n = 9 species were semi-sterile. This was shown to be associated with abnormal meiotic behavior. The former two species, when crossed, produced fully fertile hybrids. Therefore, three different karyotypes are identified among the n = 9 Brassica species. Frequent changes in the genome of the species belonging to the Brassica oleracea cytodeme could have led to the formation of accessory chromosomes present in certain accessions.