Molecular characterization of a novel polymycovirus isolated from the phytopathogenic fungus Fusarium oxysporum.

Here, a novel double-stranded RNA (dsRNA) mycovirus, tentatively designated Fusarium oxysporum polymycovirus 1 (FoPmV1), was isolated from Fusarium oxysporum, a phytopathogenic fungus that causes tobacco root rot. The genome of FoPmV1 consists of eight dsRNA segments, referred to as dsRNA1 to dsRNA8, with lengths of 2440 bp, 2276 bp, 2042 bp, 1303 bp, 1144 bp, 1064 bp, 1004 bp, and 913 bp, respectively. Sequence analysis revealed that these dsRNA segments encode 8 open reading frames (ORFs): ORF1 (771 amino acids, aa), ORF2 (699 aa), ORF3 (622 aa), and ORF4 (304 aa) encode an RNA-dependent RNA polymerase (RdRp), scaffold protein, methyltransferase, and coat protein (PASRP), respectively. While ORF5 (304 aa), ORF6 (161 aa), ORF7 (167 aa), and ORF8 (211 aa) encode proteins with unknown functions. BLAST analysis revealed that the RdRp of FoPmV1 shares the maximal sequence identity of 75.75% with the RdRp of Fusarium redolens polymycovirus 1. Phylogenetic analysis based on the RdRp sequence clustered FoPmV1 robustly within the family Polymycoviridae. Overall, this research represents the first report of a polymycovirus infecting F. oxysporum.