Inheritance of the resistance to Leptosphaeria maculans of Brassica nigra and B-juncea in near-isogenic lines of B-napus

The inheritance of resistance to Leptosphaeria maculans was studied in near -isogenic lines derived from asymmetric somatic hybrids between Brassica na pus + Brassica nigra and Brassica napus + Brassica juncea, respectively. Th e hybrids had been backcrossed to B. napus for seven generations before the genetic segregation of the blackleg resistance was determined. The results of the inheritance studies suggested that one single dominant allele contr ols the resistance in the Brassica napojuncea line, whereas two independent dominant loci were found in the Brassica naponigra line. Total leaf DNA fr om the near-isogenic lines was isolated and 89 loci were detected by hybrid ization to 66 restriction fragment length polymorphism (RFLP) markers previ ously mapped in the B. nigra genome. Out of the 89 loci, eight loci were de tected in the B. naponigra line and sia were found in the B. napojuncea lin e. RFLP markers co-segregating with blackleg resistance in adult leaves wer e also found. Two markers associated with linkage group 5 and 8, respective ly, of the B genome were found in the B. naponigra line and one marker was associated with linkage group 2 in the B. napojuncea line.