Development and chromosomal localization of genome-specific DNA markers of Brassica and the evolution of amphidiploids and n = 9 diploid species.
Ten genome-specific probes were developed from B. napus and B. oleracea genomic DNA libraries. Selection was based on polymorphism between and limited variation within genomes, permitting their localization on 6 individual C-genome chromosomes. Chromosome assignment was accomplished by using 2 sets of B. campestris-B. oleracea alien addition lines derived from B. napus and the artificially synthesized B. napus cv. Hakuran. The presence of shared fragments between A, B and C genomes indicated partial homology of the 3 genomes. However, several genome-specific markers separated these 3 genomes. The genome-specific clones developed served to confirm the parental diploid species originating the 3 amphidiploids B. napus, B. carinata and B. juncea. At least one clone suggested that B. napus has a polyphyletic origin. These clones also confirmed the close evolutionary proximity among wild species in the B. oleracea cytodeme, but no clear trends were found to suggest specific wild ancestors for the different B. oleracea horticultural types. B. oxyrrhina was distinct from other x = 9 species with most clones tested.