DETECTION OF ADDITIONAL RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS AMONG THE WEAKLY VIRULENT (NONAGGRESSIVE) AND HIGHLY VIRULENT (AGGRESSIVE) ISOLATES OF LEPTOSPHAERIA-MACULANS

Isolates of Leptosphaeria maculans were analyzed for their genetic rel atedness based on DNA restriction fragment length polymorphisms (RFLPs ), employing as Southern hybridization probes a combination of heat sh ock responsive genes (hsp70 and hsp80 from Neurospora crassa), the cut inase gene of Magnaporthe grisea, and cloned genomic DNA sequences fro m a virulent strain. Southern hybridization analysis revealed a high f requency of DNA polymorphism. Restriction fragments generated by each enzyme-probe combination resulted in distinct banding patterns, clearl y separating the isolates into two groups. The cutinase gene probe did not reveal any polymorphisms. Although the majority of the probes use d displayed RFLP profiles unique to each group, a nonaggressive isolat e, LmA, showed additional genetic characteristics in common with the v irulent pathotype.