Diversity of dsRNA Viruses Infecting Rice Sheath Blight Fungus Rhizoctonia solani AG-1 IA

Rice sheath blight, caused by Rhizoctonia solani (Kühn), is a notorious soil-borne disease prevalent in many rice-growing regions. Although several sporadic studies of mycoviruses in R. solani AG-1 IA have been reported for single strain of R. solani AG-1 IA, there have been no reports describing the distribution and diversity of mycoviruses in natural populations. In this study, 43 R. solani AG-1 IA strains collected from different locations in China were examined for the presence of dsRNA elements to confirm the presence of viral infections. Electrophoretypes showed that 16 of the 43 fungal strains (37.2%) contained dsRNAs that can be characterized as viruses. Furthermore, the species-specific reverse transcription PCR (RT-PCR) showed dsRNA bands with similar sizes do not always contain the same virus but exist as mixed mycoviral infections. Thus, our findings indicate mycoviruses infecting R. solani AG-1 IA in China are diverse, widespread and universal.