A novel double-stranded RNA mycovirus that infects Macrophomina phaseolina.

Macrophomina phaseolina is a pathogenic fungus of the family Botryosphaeriaceae that causes stem rot or leaf blight in many economically important plants. Mycoviruses exist widely in fungi, but there are only a limited number of reports on mycovirus infection in M. phaseolina. A novel dsRNA virus, tentatively named "Macrophomina phaseolina fusagravirus 1" (MpFV1), was isolated from strain 2012-19 of M. phaseolina, and its molecular features were examined. The full-length cDNA of MpFV1 comprises 9,289 nucleotides with a predicted GC content of 48.1% and two discontinuous open reading frames (ORF 1 and 2). A-1 frameshift region with two typical factors, including a shifty heptamer (GGAAAAC) and an H-type pseudoknot, was predicted in the junction region of ORF1 and ORF2. The protein encoded by ORF1 shows significant similarity to a hypothetical protein, whereas ORF2 encodes an RNA-dependent RNA polymerase (RdRp) via a ribosomal frameshifting mechanism. Homology searches and phylogenetic analysis based on the RdRp sequence suggested that MpFV1 is a new member of the proposed family "Fusagraviridae".