Description of a new putative virus infecting the conifer pathogenic fungus Heterobasidion parviporum with resemblance to Heterobasidion annosum P-type partitivirus.

The complete sequences of two double-stranded RNA segments from the fungus Heterobasidion parviporum were characterized. The larger segment (2,290 bp) contained an open reading frame encoding a putative RNA-dependent RNA polymerase (RdRp, 722 aa), while the smaller one (2,238 bp) encoded a putative coat protein of 659 aa. Based on phylogenetic analysis, the dsRNA segments constitute the genome of a new virus assigned to the family Partitiviridae and named Heterobasidion RNA virus 2 (HetRV2). The RdRp segment was clearly related to H. annosum P-type partitivirus (aa similarity of 59%) but was only distantly related to previously described viruses of H. parviporum (aa similarity 26-35%). The dsRNA could be experimentally transmitted to all five species of the Heterobasidion annosum sensu lato complex and two species of the H. insulare complex, indicating that horizontal transfer between these intersterile fungal species is possible.