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Specifically primed polymerase chain reaction (PCR) analysis was used for direct detection and identification of Rhizoctonia solaniisolates belonging to AG 1 subgroups (IA, IB, and IC) and AG 2 subgroups (2-1 and 2-2). A rapid DNA extraction method with a solution of sodium hydroxide was conducted to extract PCR templates. PCRspecific primer sets for each group were designed from sequences in the regions of the 28S ribosomal DNA of this fungus. The results of specifically primed PCR analysis showed that AG 1-IA, AG 1-IB, AG 1-IC, AG 2-1, and AG 2-2 primers sets contributed detection from the same AG isolates and could escape detection from different AG isolates at a high level of frequency. In this experiment, we suggested that our synthesized primer sets might provide a method for the direct detection and identification of AGs of R. solani.

Restriction fragment length polymorphism (RFLP) analysis for DNA products amplified by the polymerase chain reaction (PCR) was used for the direct detection of Rhizoctonia solaniAG 1 IA and AG 2-2 IIIB, R. oryzae, R. oryzae-sativaeand R. fumigatefrom the diseased rice sheaths. A rapid DNA extraction method with a solution of sodium hydroxide was conducted to extract parasite DNA from diseased rice sheaths. 28S ribosomal DNA (rDNA) derived from fungal genomic DNA extracted by the alkaline method was specifically PCR-amplified. The results of PCR-RFLP analysis for DNA samples from artificially inoculated rice sheath tissues with each Rhizoctoniespp. and the corresponding culture on the medium using two restriction enzymes, Hhaland Mspl, showed identical polymorphisms. PCR-RFLP analysis using DNA samples from naturally infected rice sheath tissues also revealed the possibility of direct diagnosis of R. solaniAG 1IA, R. oryzaeand R. oryzae-sativae.

Total-cellular fatty acid compositions of 34 isolates of Rhizoctonia solanibelonging to intraspecific groups (ISGs) of anastomosis group (AG) 2, i.e., AG 2-1, AG 2-2 IIIB (mat rush), AG 2-2 IV (sugar beet), AG 2-2 LP (turfgrass), and AG 2- 3 (soybean), were compared. The major fatty acids identified were palm/tic, stearic, and oleic acids. Principal component analysis based on the percentage composition of total cellular fatty acids revealed consistently low variability among isolates of a single ISG of AG 2. Average linkage cluster analysis showed that isolates obtained from turfgrass representing a newly proposed group, AG 2-2 LP, were differentiated from other AG 2 ISGs. Isolates of another newly proposed group AG 2-3, from diseased soybean were also closely related to AG 2-1 and AG 2-2 IIIB but distinguishable from the AG 2-1 and AG 2-2 LP isolates by the average linkage cluster analysis. These results suggested that the percentage composition of total-cellular fatty acids is a distinct characteristic for the five ISGs belonging to AG 2, and fatty acid analysis is useful for the differentiation and characterization of these ISGs of AG 2 in R. solani.