INVESTIGATION OF GENETIC RELATEDNESS AMONG ANASTOMOSIS GROUPS OF RHIZOCTONIA-SOLANI USING CLONED DNA PROBES

Thirty-eight isolates of Rhizoctonia solani, representing 10 anastomosis groups (AGs) and from diverse geographic origins, were assayed for restriction fragment length polymorphisms (RFLPs). Whole-cell DNAs were digested separately with Eco RI, Bgl II, Hind III, and Pst I restriction enzymes and probed with cloned rDNA from Armillaria ostoyae in Southern hybridizations. Anastomosis groups 1,2,3, 6 and subgroups 1-1 and 2-1 have one or more unique patterns that are not found in other groups. Isolates belonging to AG-4, 5, 7, 8, 9, and BI produced a variety of restriction patterns, some of which are shared among them. Intragroup RFLP variation was observed in all AGs with the highest level of variation found among isolates belonging to AG-2 and its subgroups AG-2-1 and AG-2-2. RFLPs in nuclear DNA also were examined by hybridization to random nuclear probes generated from the nuclear DNA of an isolate of AG-3. Hind III- or Pst I- digested nuclear DNAs of isolate PSU-10-07 were cloned in the plasmid vector pBR322. Five random recombinant clones were used in Southern hybridizations to probe DNAs of R. solani isolates. all of these probes hybridized only to AG-3 isolates indicating that they are group specific. The specificity of the hybridization patterns suggests that these probes consist of DNA sequences with one or a few copies per genome. Based on the evidence presented, these probes have the potential of being a useful diagnostic tool in the study of AG-3.