COMPARISON OF THE GENETIC MAPS OF BRASSICA-NAPUS AND BRASSICA-OLERACEA

The genus Brassica consists of several hundreds of diploid and amphidi ploid species. Most of the diploid species have eight, nine or ten pai rs of chromosomes, known respectively as the B, C, and A genomes. Gene tic maps were constructed for both B. napus and B. oleracea using most ly RFLP and RAPD markers. For the B. napus linkage map, 274 RFLPs, 66 RAPDs, and two STS loci were arranged in 19 major linkage groups and t en smaller unassigned segments, covering a genetic distance of 2125 cM . A genetic map of B. oleracea was constructed using the same set of R FLP probes and RAPD primers. The B. oleracea map consisted of 270 RFLP s, 31 RAPDs, one STS, three SCARs, one phenotypic and four isozyme mar ker loci, arranged into nine major linkage groups and four smaller una ssigned segments, covering a genetic distance of 1606 cM. Comparison o f the B. napus and B. oleracea linkage maps showed that eight out of n ine B. oleracea linkage groups were conserved in the B. napus map. The re were also regions in the B. oleracea map showing homoeologies with more than one linkage group in the B. napus map. These results provide d molecular evidence for B. oleracea, or a closely related 2n = 18 Bra ssica species, as the C-genome progenitor, and also reflected on the h omoeology between the A and C genomes in B. napus.