Abstract

This study investigated the production of pectic enzymes by the phytopathogenic fungus Rhizoctonia solani AG 8 (ZG1–1). The principal types of pectic enzymes produced during growth in citrus–pectin medium are polygalacturonase and pectin lyase. Electrophoretic analysis of culture supernatant proteins revealed a number of proteins associated with virulence. Isoelectric focusing of proteins and staining for pectic enzyme activity showed that all field isolates synthesised a complex mixture of pectic enzymes. There were no differences in the pectic enzyme profile of highly and weakly virulent isolates, or between isolates from sites hundreds of kilometres apart. Pectic enzymes did segregate clearly among single-spore progeny of a highly virulent field isolate. The results suggest that there are additional factors that contribute to the virulence of these isolates.