Preliminary Study Of The Virus Of Sclerotinia Sclerotiorum Strain SNZ1-3-5

Mycoviruses (or fungal viruses) are widely spread in the fungal kingdom. The discovery and characterization of more novel mycoviruses might supply abundant viral material to research the origin, ecology and evolutionary pathways of mycoviruses. In present study, the biological characterization of two mycoviruses and their host Sclerotinia sclerotiorum strain SNZ1-3-5, isolated from a diseased rapeseed plant at Shanxi province, were analyzed. The results of present study are given below:Compared with the control strain without carrying the fungal virus Ep-1PNA367, we found that the growth rate and the production of oxalic acid capacity of the strains SNZ1-3-5significantly decreased, while colony morphology of SNZ1-3-5was similar to that of strain Ep-1PNA367. Virulence test on the detached leaves of rapeseed revealed that strain Ep-1PNA367could cause typical diseased lesions at24hours post-inoculation (hpi) and develop diseased lesions with3.2cm in diameter at48hpi, whereas strain SNZ1-3-5could not cause diseased lesion at24hpi and develop diseased lesions with1.5cm in diameter at48hpi. Therefore, strain SNZ1-3-5is a hypovirulent strain of S. sclerotiorum.We also detected that strains SNZ1-3-5contains at least two dsRNA fragment: approximately9.0kb and5.0kb, which were named the SL-the dsRNA and SS-the dsRNA respectively. After cDNA cloning and bioinformatics analysis, we found that the known sequence of the SL-dsRNA has97%genome homology with the fungus Sclerotinia the virus SsHVl/SZ-150of Sclerotinia weak virus1(S. sclerotiorum hypovirus1, SsHV1/SZ-150), so the virus belongs to different strains of the same virus. The homology between the known sequence of the SM-dsRNA and part of the whole virus family shield shell mold RNA viruses (Coniothyrium minitans RNA virus, CmRV) was up to55%, so the former is named for Sclerotinia virus1(Sclerotinia sclerotiorum Totivirus1/SNZ1-3-5, SsTV-1/SNZ1-3-5). These results suggest that strains of SNZ1-3-5contains two fungal viruses, which belongs to Hypoviridae and Totiviridae respectively.By analysis of the strains SNZ1-3-5protoplast regeneration strain, we got the regeneration strains SNZ1R20,which includes SsTV-1but not SsHV1. The biological characteristics analysis revealed that the colony morphology of the strains SNZ1R20was significantly different from the original strain, which had more aerial mycelium and the curly hyphal tips; Analysis of pathogenicity showed that the strains SNZ1R20rape leaves completely lost pathogenicity. This present results showed that SsTV-1/SNZ1-3-5without SsHV1/SNZ1-3-5affects colony morphology and virulence of S.sclerotiorum.