Characterization of a novel mitovirus isolated from the phytopathogenic fungus Fusarium pseudograminearum

Mycoviruses are widespread in all major groups of plant-pathogenic fungi. So far, only one mycovirus has been reported to be associated with Fusarium pseudograminearum, the causal agent of Fusarium crown rot of wheat. In this study, a double-stranded RNA (dsRNA) segment was isolated from F. pseudograminearum strain JW2-1, and the sequence of its full-length cDNA (3077 nucleotides) was determined. Sequence analysis using the fungal mitochondrial genetic code (UGA coding for tryptophan) indicated that a single large open reading frame (ORF) is present on the positive strand of this dsRNA segment. The ORF encodes a putative RNA-dependent RNA polymerase (RdRp) of 748 amino acids (aa) with a molecular mass of 83.46 kDa. BLASTp analysis revealed that its aa sequence was 28.49-44.03% identical to those of viruses of the family Mitoviridae, with the most similarity to the corresponding RdRp sequences of Ophiostoma mitovirus 1c (44.03% identity) and Ophiostoma mitovirus 1b (40.33% identity). Phylogenetic analysis showed that this mycovirus, designated as "Fusarium pseudograminearum mitovirus 1" (FpgMV1), should be classified as a member of a new species in the earlier proposed genus "Duamitovirus" within the family Mitoviridae. To our best of our knowledge, this is the first report of a mitovirus infecting F. pseudograminearum.