Abstract
Sclerotinia sclerotiorum is a notorious phytopathogenic fungus that harbors diverse mycoviruses. A novel positive-sense single-stranded RNA virus, Sclerotinia sclerotiorum alphaflexivirus 2 (SsAFV2), was isolated from the hypovirulent strain 32-9 of S. sclerotiorum, and its complete genome was determined. The SsAFV2 genome contains 7,162 nucleotides (nt), excluding the poly (A) structure, and is composed of four open reading frames (ORF1-4). ORF1 encodes a polyprotein that contains three conserved domains: methyltransferase, helicase, and RNA-dependent RNA polymerase (RdRp). The ORF3 putative encodes coat proteins (CP), with ORF2 and ORF4 encoding hypothetical proteins of unknown functions. Phylogenetic analysis revealed that SsAFV2 clustered with Botrytis virus X (BVX) based on multiple alignments of helicase, RdRp, and CP, but the methyltransferase of SsAFV2 was most closely related to Sclerotinia sclerotiorum alphaflexivirus 1, suggesting that SsAFV2 is a new member of the Botrexvirus genus within the Alphaflexiviridae family, and also revealed the occurrence of potential inter-species horizontal gene transfer events within the Botrexvirus genus during the evolutionary process. Our results contribute to the current knowledge regarding the evolution and divergence of Botrexviruses.