Abstract
Two hundred fifty random sequence primers were used to screen a pair of bulked DNA samples derived from open-pollinated progenies of Japanese pear 'Osa Nijisseiki' to identify RAPD (randomly amplified polymorphic DNA) markers linked to the susceptible A gene of black spot disease. Only one primer, CMNB41, among three primers which generated DNA fragments, was present in the susceptible bulk, but not in the resistant one. CMNB41 generated the DNA fragment, CMNB41/2350, which co-segregated with the susceptible A gene among the selfpollinated F1 progenies of 'Osa Nijisseiki'. This RAPD marker CMNB41/2350 is at a distance of about 3.1 cM from the susceptible A gene. Moreover, the frequency of occurrence of the CMNB41/2350 marker in susceptible cultivars and selected progenies of 'Osa Nijisseiki' x 'Oharabeni' was 96%.
