PCR With Specific Primers for Detection of Rhizoctonia solani Anastomosis Groups Reveals Lack of Specificity

Several specific primers based on the internal transcribed spacer (ITS) region of rDNA have been used to discriminate anastomosis groups (AGs) and subgroups in Rhizoctonia solani, but the efficacy of these primers was not evaluated considering several known AGs. This study aimed to evaluate the efficacy of seven PCR-specific primers for the detection of four AGs and subgroups of R. solani (AG-1 IA, AG-1 IB, AG-2-1, AG-3 PT, AG-3 TB, AG-4 HGI, and AG-4 HGII). Thirteen isolates of R. solani and seven isolates of binucleate Rhizoctonia belonging to different AGs and subgroups were used in the detection assays and were amplified and sequenced using ITS1 and ITS4 universal primers to confirm the previous identification of AGs and the viability of the DNA samples. In addition, three isolates of unrelated fungal species (Fusarium oxysporum, Macrophomina phaseolina, and Sclerotium rolfsii) were tested simultaneously with each primer set above as a negative control. All primers tested nonspecifically amplified other AGs, and most of the primers produced bands for unrelated fungal species. Therefore, the exclusive use of these primers under the PCR conditions should be avoided due to the lack of accuracy in the results.