Molecular characterization of some Elsinoe isolates from leguminous hosts

Pathogenicity of Elsinoe isolates from Phaseolus coccineus, P. lunatus, P. vulgaris and Vigna unguiculata was studied and the relatedness of the isolates examined at the molecular level using eight random 10-mer primers to amplify total DNA (RAPDs). Isolates differed markedly in their pathogenicity to the various hosts and there was some evidence that those from P. coccineus and P. vulgaris were different pathotypes. The isolate from V. unguiculata was the only one that was virulent on this host and was nonvirulent on P. vulgaris. A RAPD-based dendrogram with a cophenetic correlation coefficient of 0.975 was generated using the NTSYS-pc computer program. A UPGMA cluster analysis based on the RAPD banding pattern of the eight primers ranked Elsinoe phaseoli isolates from Phaseolus spp. into two major subgroups. One subgroup was composed of isolates from P. lunatus and P. vulgaris, and the other from P. coccineus, suggesting some specialization within the species. The isolate from Vigna unguiculata clustered separately from the Phaseolus isolates, as did the Elsinoe outgroups from Citrus, Protea and Leucospermum. These results suggest that the isolate from Vigna unguiculata could be an undescribed species of Elsinoe.