A novel hexasegmented virus isolated from the phytopathogenic fungus Verticillium nonalfalfae

Abstract

In this study, we describe a novel virus, tentatively named Verticillium nonalfalfae virus M (VnaVM), identified in the phytopathogenic fungus Verticillium nonalfalfae isolated from hop (Humulus lupulus L.). The VnaVM genome consists of six double-stranded RNA (dsRNA) segments ranging from 1051 to 2401 bp. DsRNAs 1–3 encode an RNA-dependent RNA polymerase (RdRp), a hypothetical protein and a methyltransferase (MTR), respectively, while dsRNA6 encodes a proline-alanine-serine-rich protein (PASrp). These four proteins share less than 58% amino acid identity with homologs encoded by viruses in the family Polymycoviridae. Products encoded by dsRNAs 4 and 5 show no similarity to known proteins, and their roles in the viral life cycle are unknown. Phylogenetic analysis of RdRp amino acid sequences, together with genome organization and pairwise identity values, supports classifying VnaVM as a representative of a novel species within the genus Multimycovirus (family Polymycoviridae). To our knowledge, this is the first report of a polymycovirid infection in a member of the genus Verticillium.