Characterization of a novel single?stranded RNA mycovirus relatedto invertebrate viruses from the plant pathogen Verticillium dahliae

AbstractFungal viruses, also known as mycoviruses, are widespread in all major groups of fungi. Mycoviruses from plant pathogenscan reduce the virulence of their host fungus and have therefore potential as biological control agents. This has spurred theidentification of novel mycoviruses in plant pathogens, research which is greatly contributing to our understanding of theseorganisms. In this work, we report the characterization of a novel monopartite mycovirus from Verticillium dahliae, the maincausal agent of Verticillium wilt. This novel mycovirus, which we termed Verticillium dahliae RNA virus 1 (VdRV1), wasidentified in three different isolates of V. dahliae collected in olive growing areas of the Guadalquivir valley, southern Spain.We determined that the VdRV1 genome is a positive (+) single-stranded (ss) RNA, 2631 nucleotides in length, containingtwo open reading frames. VdRV1 showed few similarities with known mycoviruses, only with a group of unassigned (+)ssRNA mycoviruses which are related to plant viruses classified within the family Tombusviridae. However, phylogeneticanalysis revealed that VdRV1 and the unassigned (+) ssRNA mycoviruses have a closer relationship with recently reportedinvertebrate viruses. This result indicates that as more viral sequences become available, the relationships of mycoviruseswith viruses from other hosts should be reexamined. Additionally, the work supports the hypothesis of a heterogeneousorigin for mycoviruses