CHARACTERIZATION OF BRASSICA-NIGRA CHROMOSOMES AND OF BLACKLEG RESISTANCE IN B-NAPUS-B-NIGRA ADDITION LINES

Brassica napus-B. nigra addition lines were previously created using t he variety 'Darmor' as the oilseed rape genetic background. Two isozym e loci and 46 RAPD markers were added on five different B. nigra chrom osomes. The oilseed rape variety used was highly susceptible to blackl eg at the cotyledon stage and only the addition of chromosome 4 gave t he same level of blackleg resistance as B. nigra. This resistance was efficient whatever the isolates used. A significant effect on the deve lopment of stem canker under field conditions was observed only for th e line carrying chromosome 4 which was more resistant than the suscept ible control. The potential effects of two other chromosomes have to b e confirmed. Fl hybrids obtained by crosses between two highly suscept ible lines and the monosomic addition line carrying chromosome 4 were examined under field conditions. No effect of the oilseed rape genetic background on the expression of resistance was detected. The introduc tion of this resistance and mapping of the gene(s) into oilseed rape v arieties are discussed.