Characterization of a Novel Hypovirus RsHV4 in the Phytopathogenic Fungus Rhizoctonia solani

WANG Peng; LI Duhua; ZHANG Shaohui; YANG Mengning; AN Hongliu; FANG Shouguo; DENG Qingchao; GUO Lingfang; ZHANG Songbai

doi:10.15933/j.cnki.1004-3268.2024.02.010

Abstract：In order to find a new hypovirus in Rhizoctonia solani and to provide a new biological control resource for corn sheath blight,a new virus RsHV4(Rhizoctonia solani hypovirus 4)was discovered by dsRNA extraction from the R.solani strain ZYFG11.The taxonomic status and biological characteristics such as hypovirulence activity of the new virus RsHV4 were determined by genomic cloning,phylogenetic analysis,growth characterization and biological inoculation.The result showed that RsHV4 was a positive single-stranded RNA virus with the genome of 18702 nt,encoding a polyprotein of 5540 aa.Phylogenetic analysis showed that RsHV4 belonged to the genus Thetahypovirus of the family Hypoviridae and shared the highest identity of 59.46%with the polyprotein of Sclerotium rolfsii hypovirus 1.The mycelial growth rates of avirulent strain JSJH6 and virulent strain ZYFG11 were 0.50 cm/d and 0.41 cm/d,the time of mass formation of sclerotium was 5 and 7 d,the total weights of the 50 largest sclerotia were 0.27 g and 0.11 g after ten days of strain growth,respectively,these results indicating that the mycelial growth of the virulent strain ZYFG11 was slowed down,the sclerotium formation was delayed,and the sclerotium size was reduced.Two weeks after biological inoculation,the disease spot area of the second sheath and the third sheath of maize plants inoculated with virulent strain ZYFG11 accounted for 30%and 10%respectively,while the disease spot area of the second sheath and the third sheath of plants inoculated with avirulent strain JSJH6 accounted for 100%,indicating that the pathogenicity of virulent strain ZYFG11 decreased significantly.In conclusion,this study identified a novel hypovirus RsHV4 from R.solani,which can affect the biological characteristics and pathogenicity of host fungi,providing a potential virus resource for the control of corn sheath blight.