ISOZYME VARIATION AND GENETIC RELATEDNESS IN BINUCLEATE RHIZOCTONIA SPECIES

Fifty isolates of binucleate Rhizoctonia representing 12 Japanese and five North American anastomosis groups (AGs) were characterized by iso zyme electrophoretic patterns. Of the 23 enzyme systems screened, eigh t enzymes with a total of 63 phenotypes were applied to study the gene tic relationship among the AGs. Hexokinase and malate dehydrogenase di splayed the most polymorphic banding patterns. Cluster analysis of iso zyme bands generated four distinct groups (I, II, III, and IV). Group I was represented by all AG-G isolates. Group II was subdivided into t wo subgroups (IIA and IIB). Subgroup IIA was made up of the cross-anas tomosing groups AG-D/CAG-1 and AG-E/CAG-3, and subgroup IIB was made u p of groups AG-F/CAG-4, AG-I, and CAG-5. Group III included isolates b elonging to AG-K and CAG-2 with one isolate each of AG-A and AG-B(o). Group IV consisted mainly of AG-Bb isolates. AG-A, AG-Ba, AG-C, and AG -O isolates were placed in different groups and were considered geneti cally diverse. Isozyme groups of binucleate Rhizoctonia were consisten t with prior groupings determined by hyphal anastomosis and by DNA res triction pattern analysis. The present study provides evidence that is ozyme phenotypes are good indicators of genetic diversity among anasto mosis groups of binucleate Rhizoctonia species.