Complete genome characterization of a new alphapartitivirus identified in the ectomycorrhizal fungus Lactarius mediterraneensis

Viruses that naturally infect fungi capable of forming mycorrhizal symbioses remain poorly studied. In the present study, a new partitivirus associated with the basidiomycete mycorrhizal fungus Lactarius mediterraneensis was identified and characterized, and it was designated as Lactarius mediterraneensis partitivirus 1 (LmPV1). The complete genome of LmPV1 was determined through high throughput sequencing of double-stranded RNA (dsRNA) extracts and confirmed by Sanger sequencing of RLM-RACE PCR amplicons. T he genome comprises two dsRNA segments, 1899 bp and 1957 bp, each containing a single open reading frame (ORF) a putative RNA-dependent RNA polymerase (RdRp) and a capsid protein (CP). Comparative analysis using BLASTp revealed the closest matches to be Sarcosphaera coronaria partitivirus ANK VIR-52 (65.22% identity for RdRp) and Rosellinia necatrix partitivirus 26 (26.53% identity for CP). Phylogenetic reconstruction based on the RdRp sequence positioned LmPV1 within a cluster exclusively composed of Alphapartitivirus species from the Partitiviridae family. Given these molecular data, LmPV1 is proposed as a novel member of the Alphapartitivirus genus. This work provides the first documented evidence of a partitivirus infecting the mycorrhizal basidiomycete L. mediterraneensis.