Identification of the different Brassica nigra chromosomes from both sets of B-oleracea B-nigra and B-napus B-nigra addition lines with a special emphasis on chromosome transmission and self-incompatibility

The F-1 hybrids produced after crosses between B. nigra and B. oleracea were backcrossed two or three times to B. oleracea. Among the 14 plants analysed, five were monosomic addition lines (2n = 19), six were double monosomic addition lines (2n = 20) and three had three or four additional chromosomes. From these lines, 14 isozyme and 80 RAPD loci were localized on the eight chromosomes of B. nigra. The comparison between B. napus-B. nigra, from which five B. nigra chromosomes were already described, and the new set of B. oleracea-B. nigra addition lines was performed using five isozyme and 22 common RAPD loci. The homology of the common RAPD loci was confirmed by hybridization of the two sets of addition lines as well as the presence of duplicated loci on different chromosomes. For the five added chromosomes available on the two genetic backgrounds, i.e. B. napus and B. oleracea, using isozyme markers, the chromosome transmission rate was studied from backcross progeny using the recurrent parent either as male or as female and from the selfing of monosomic addition lines. For each chromosome, no difference was detected between male and female transmission except for chromosome 3. This latter presented a percentage of female transmission of around 20%, close to the ones observed for the other chromosomes, but a very low male transmission (1.3%). The analysis from restriction enzyme digests of PCR products, obtained from primers selected in highly conserved regions of self-incompatible genes, suggested that the chromosome 3 probably carried the SLG-B. nigra locus.