Mycovirus-induced hypovirulence offers promise as a sustainable strategy for managing forest diseases. Two mycoviruses have been found naturally infecting Fusarium circinatum, the causal agent of pine pitch canker (PPC), yet their role in fungal pathogenicity remains unclear. This study focused on Unuamitovirus fuci2 (FuciMV2-1), assessing its impact on fungal virulence through pathogenicity assays and dual RNA-seq analysis of infected Pinus radiata seedlings. Pathogenicity tests revealed no significant differences in virulence between virus-infected and virus-cured fungal strains. Similarly, host transcriptomic responses were largely comparable between treatments. Nevertheless, seedlings infected with the FuciMV2-1-carrying strain showed slightly stronger activation of the jasmonic acid pathway and cell wall defence via PME inhibitor expression. In contrast, virus-cured strains may influence oleoresin biosynthesis. At the fungal level, transcriptomic changes were minimal, though the down-regulation of the VE1 gene in the presence of FuciMV2-1 suggests a potential role in virulence regulation. Additional studies are needed to further investigate the effects of F. circinatum mycoviruses and to clarify their potential role in PPC control.
