Molecular characterization of a novel single-stranded RNA virus, ChRV1, isolated from the plant-pathogenic fungus Colletotrichum higginsianum

In this study, a novel single-stranded RNA virus was isolated from the plant-pathogenic fungus Colletotrichum higginsianum strain HTC-5, and the virus was named "Colletotrichum higginsianum ssRNA virus 1" (ChRV1). The complete genome of ChRV1 is 3850 nucleotides in length with a GC content of 52% and contains two in-frame open reading frames (ORFs): ORF1 (smaller) and ORF2 (larger). ORF1 encodes a protein with the highest sequence similarity to proteins encoded by Phoma matteucciicola RNA virus 1 (PmRV1, 47.99% identity) and Periconia macrospinosa ambiguivirus 1 (PmAV1, 50.73% identity). ORF2 encodes a protein with a conserved RNA-dependent RNA polymerase (RdRp) domain with similarity to the RdRps of PmRV1 (61.41% identity) and PmAV1 (60.61% identity), which are recently reported unclassified (+) ssRNA mycoviruses. Phylogenetic analysis of the RdRp domain showed that ChRV1 grouped together with PmRV1, PmAV1, and other unclassified (+) ssRNA mycoviruses and had a distant relationship to invertebrate viruses and plant viruses of the family Tombusviridae. This is the first report of a novel (+) ssRNA virus infecting the phytopathogenic fungus C. higginsianum.