Monoclonal anti-dsRNA antibody-based metagenomics (MADAM) reveal Pyricularia oryzae mycovirome

Background.Mycoviruses infect fungal cells and represent important components of the global virome with potential biological control applications. The rice blast pathogen Pyricularia oryzae causes devastating crop losses worldwide, yet its mycovirus diversity remains understudied. While traditional dsRNA extraction remains a standard method for virus discovery, recent advancements, such as monoclonal antibody (mAb)-based dsRNA enrichment, offer improved specificity and sensitivity for viral detection. Methods.We developed the monoclonal anti-dsRNA antibody-based metagenomics (MADAM) approach, integrating dsRNA enrichment using 2G4 monoclonal antibody, sequence-independent reverse transcription-PCR with random octamer primers, and Oxford Nanopore Technologies sequencing. Total RNA was extracted from four P. oryzae isolates collected from Yuanyang rice terraces (Yunnan, China). After nuclease treatment, dsRNA was enriched using anti-dsRNA antibodies, followed by strand-switching cDNA synthesis, PCR amplification, and MinION sequencing. Genome gaps and terminal sequences were resolved through targeted RT-PCR and modified 3' RACE approaches. Results.MADAM achieved high viral read recovery rates (46.9-72.7%) and identified 18 P. oryzae-associated RNA viruses across seven families: Botourmiaviridae, Deltaormycoviridae, Mymonaviridae, Partitiviridae, Polymycoviridae, Splipalmiviridae, and Ambiguiviridae. Nearly complete to complete genomes (ranging from 1,226 to 6,085 nucleotides) were recovered, with sequence coverage spanning 88-100%. Co-infections occurred in three out of four isolates. Notable discoveries included the first deltaormycovirus in P. oryzae, a putative novel Botourmiaviridae member, and an additional genomic segment of a polymycovirus. The method detected positive-sense, negative-sense ssRNA, and dsRNA viruses, demonstrating broad applicability.