A novel polymycovirus infecting the entomopathogenic fungus Metarhizium brunneum

In this study, at least four distinct double-stranded RNA viruses, including two partitiviruses, one bipartite virus, and a novel polymycovirus, were detected in the entomopathogenic fungus Metarhizium brunneum strain RCEF0736. We describe the characterization of one of these viruses, a novel polymycovirus, which we have named "Metarhizium brunneum polymycovirus 1" (MbPmV1). The genome of MbPmV1 has four dsRNA segments, ranging from 1153 to 2421 bp in length. dsRNA1, 2, and 3 of MbPmV1 each contain a single large open reading frame (ORF), while dsRNA4 has two ORFs. BLASTp analysis indicated that dsRNA1, 2, 3, and 4 of MbPmV1 have a high degree of similarity to the putative RdRp (59.45%), serine protease (44.22%), putative methyltransferase (48.76%), and proline-alanine-serine-rich protein (PASrp) (52.80%), respectively, of Phaeoacremonium minimum tetramycovirus 1 (PmTmV1). MbPmV1 was grouped in a cluster with members of the genus Polymycovirus and was most closely related to PmTmV1 in the phylogenetic tree. Thus, we propose that MbPmV1 represents a novel species of the genus Polymycovirus, family Polymycoviridae. To our knowledge, this is the first report of a polymycovirus in a member of the genus Metarhizium.