Identification and complete genome characterization of two new partitiviruses hosted by the lichenized fungus Calogaya decipiens.

UNLABELLED: Lichens represent complex symbiotic systems consisting of a fungal partner and photosynthetic microorganisms, and they could also harbor diverse associated microbiota including viruses. Despite increasing interest in mycoviruses from filamentous fungi, viruses infecting lichenized fungi remain poorly characterized. In this study, we identified and molecularly characterized two novel double-stranded RNA viruses infecting the lichenized fungus Calogaya decipiens (Arnold) Arup, Frödén & Søchting. Viral sequences were detected from dsRNA-enriched extracts of a surface-sterilized lichen thallus using random PCR amplification and high-throughput sequencing. Genome analyses revealed that both viruses possess bipartite genomes typical of members of the family Partitiviridae, each consisting of two dsRNA segments encoding an RNA-dependent RNA polymerase (RdRp) and a capsid protein (CP). The genome segments of Calogaya decipiens partitivirus 1 (CdPV1) and Calogaya decipiens partitivirus 2 (CdPV2) range from 1861 to 2283 bp and contain single open reading frames. Phylogenetic analysis based on RdRp amino acid sequences placed CdPV1 within the genus Alphapartitivirus, whereas CdPV2 clustered with members of the genus Betapartitivirus. Conserved catalytic motifs characteristic of dsRNA virus polymerases were identified in both RdRps. Sequence identity comparisons with related viruses supported the classification of CdPV1 and CdPV2 as representatives of two novel partitivirus species. To our knowledge, this study represents the first report of mycoviruses infecting the lichenized fungus C. decipiens. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13337-026-00966-w.