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 the variety 'Darmor' as the oilseed rape genetic background. Two isozyme loci and 46 RAPD markers were added on five different B. nigra chromosomes. The oilseed rape variety used was highly susceptible to blackleg at the cotyledon stage and only the addition of chromosome 4 gave the same level of blackleg resistance as B. nigra. This resistance was efficient whatever the isolates used. A significant effect on the development of stem canker under field conditions was observed only for the line carrying chromosome 4 which was more resistant than the susceptible control. The potential effects of two other chromosomes have to be confirmed. Fl hybrids obtained by crosses between two highly susceptible 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 introduction of this resistance and mapping of the gene(s) into oilseed rape varieties are discussed.