ISOLATION AND MOLECULAR CHARACTERIZATION OF MITOVIRUS ASSOCIATED WITH SCLEROTINIA SCLEROTIORUM AND ITS EFFECT ON FUNGAL BIOLOGY

The fungus Sclerotinia sclerotiorum is one of the most important plant pathogens with wide host range. In order to study of mycoviruses, the Cea isolate of this fungus was obtained from mycological herbarium of University of Tehran. Using column chromatography with CF-11 cellulose, isolation of dsRNA was performed from lyophilized mycelia. Eventually, a dsRNA segment was obtained which was approximately 2.5 kbp in size. Molecular cloning and partial sequencing of this segment revealed significant sequence similarity at amino acid level to RdRp encoded by Mitoviruses. It was closest to the isolates Mitovirus 2/NZ1 from New Zealand and Mitovirus 2/KL1 from the United States with 94% and 87% similarity, respectively. Attempt to eliminate themitovirus was unsuccessful using hyphal tip excision in combination with Cycloheximide treatment at concentration of 30, 40 and 50 μg/ml. The mitovirus was transmitted from the originally infected Cea isolate to Lekh isolate via hyphal anastomosis. Potential of vertical transmission was examined and mitovirus was present in 55% of the ascospores. The mitovirus infection reduced mycelium linear growth. Pathogenicity test on celery stalks and soybean leaves showed the presence of this mitovirus reduced virulence of S. sclerotiorum.