SELECTION OF STABLE BRASSICA-NAPUS BRASSICA-JUNCEA RECOMBINANT LINES RESISTANT TO BLACKLEG (LEPTOSPHAERIA-MACULANS) - 2 - A TO AND FRO STRATEGY TO LOCALIZE AND CHARACTERIZE INTERSPECIFIC INTROGRESSIONS ON THE BRASSICA-NAPUS GENOME

A new strategy to localise and characterise interspecific introgressio ns in the genus Brassica is presented. It consists of the localisation of RAPD specific markers from the donor species (B. juncea) by RFLP o n a genetic map of the recipient (B. napus) and on the observation of the disappearance of rapeseed markers in recombinant lines. With this method, we localised an interspecific introgression of B. juncea, whic h confers blackleg resistance at the cotyledon stage in B. napus, on t he linkage group DY17 of the previously determined B. napus genetic ma p. The estimated size of the substituted B, napus fragment was 39 cM, and the resistance gene was introgressed into the rapeseed genome by h omologous recombination. The significance of the different strategies used and the implication of these results in breeding programs are dis cussed.