Molecular characterization of a novel non-segmented double stranded RNA mycovirus infecting the phytopathogenic fungus Botryosphaeria dothidea.

Botryosphaeria dothidea is a prevalent pathogen of woody plants with a global distribution. In this study, we identified a novel mycovirus from the B. dothidea strain ZM200473, which we have tentatively designated "Botryosphaeria dothidea non-segmented dsRNA virus" (BdNSRV1). The genome of BdNSRV1 is composed of dsRNA that spans 2,902 base pairs and contains two non-overlapping open reading frames (ORF1 and ORF2). ORF1 encodes a hypothetical protein consisting of 316 amino acids with a molecular weight of 35.0 kDa, and this protein shares similarity to the coat proteins of several mycoviruses. ORF2 encodes a protein of 561 amino acids with a molecular weight of 66.0 kDa, which includes a conserved RNA-dependent RNA polymerase (RdRp). Sequence comparisons and phylogenetic analysis indicated that BdNSRV1 establishes a well-supported independent clade alongside members of the recently established genus Unirnavirus, being most closely related to Lasiodiplodia pseudotheobromae mycovirus 1 (LpMyV1), with 70.74% amino acid sequence identity in the RdRp. Therefore, BdNSRV1 should be classified as a novel non-segmented dsRNA mycovirus of the genus Unirnavirus and is the first characterized non-segmented virus associated with B. dothidea.