Identification at strain level of Rhizoctonia solani AG4 isolates by direct sequence of asymmetric PCR products of the ITS regions.

The relatedness of nine isolates of Rhizoctonia solani, belonging to anastomosis group (AG) 4, and one isolate of AG1 was determined by comparative sequence analysis based on direct sequencing of PCR-amplified ribosomal DNA [the internal transcribed spacer (ITS) region and the 5.8 s ribosomal DNA]. The 5.8 s rDNA is completely conserved, but both ITS regions show variation among strains. AG1 was an outgroup based on anastomosis ability and RFLP analyses. Phylogenetic analyses based on the ITS sequences suggest that the analyzed AG4 strains can be divided into three groups that correlate with habitat and virulence.