Molecular Characterization of the Subgroup Differentiation in Binucleate Rhizoctonia AG-Ba, causal agents of rice sclerotial diseases.

Rhizoctonia spp. consists of geneticallyincompatible strain groups (anastomosis group, AG)distinguished by lack of anastomosis between hyphae of strains.In recent years, nucleotide sequences of rDNA-ITS region arewidely used for the analysis of molecular diagnoses,classifications of DNA barcode and evolutions of plantpathogenic fungi. In this study, six different taxa of genusRhizoctonia, includes three genus Thanatephorus, Waitea andCeratobasidium on the teleomorph, of rice and weed sclerotialfungi, were classified with PCR-RFLP band patterns. Eightisolates of bincleate Rhizoctonia AG-Ba, the gray sclerotialfungus, showed three banding patterns, Type I (4 isolates),Type II (2 isolates) and a mixed-banding type (2 isolates). Todetermine whether the mixed-banding type arose from genomemixing between Type I and II, we cloned PCR products of ITSregions include 5.8S rDNA sequence. Twelve sequencesderived from each isolates were sequenced from bothdirections and multiply aligned. The cluster analysis based onthe multiple alignment showed that sequences derived fromeach isolate divided into two clades. The sequences derivedfrom mixed-banding type isolates were divided into both twoclades, revealing these isolates caused from genome crossingbetween Type I and II. To confirm this interpretation,microsatellite fingerprints of 54 isolates of binucleateRhizoctonia AG-Ba were investigated and the fingerprintpatterns were analyzed with cluster analysis. Unexpectedly,fingerprint patterns derived from 54 isolates were divided intothree clades, unlike results of ITS sequencing. The result ofcluster analysis likely to cause by unique banding patterns ofthe mixed type isolates, although banding patterns of fewisolates showed mixed character of Type I and II. Because ofsuperior information of microsatellite fingerprinting, theresults lead us to interpretation that Rhizoctonia AG-Baisolates should be classified into at least three subgroups