Abstract Diseases caused by Sclerotinia sclerotiorum and Fusarium spp. result in substantial yield losses and deterioration of grain quality. The entomopathogenic fungus (EPF) Beauveria bassiana inhibits a wide range of phytopathogens in vitro and establishes symbiotic relationships with plants to induce systemic resistance against fungal infections. While certain mycoviruses are known to influence the biological traits and virulence of B. bassiana toward insect pests, their effects on phytopathogens remain underexplored. In this study, we examined the effects of the mycovirus Beauveria bassiana orthocurvulavirus 1 (BbOCuV1) on its fungal host. Specifically, we assessed the effects of BbOCuV1 on host biological characteristics, as well as its ability to inhibit the phytopathogens S. sclerotiorum and F. asiaticum in vitro, and its role in enhancing plant resistance following endophytic colonization. Our results showed that BbOCuV1 infection significantly enhanced the biological fitness of B. bassiana, increasing its growth rate, sporulation, and biomass. This enhancement also manifested in functional activity. The virus-infected fungus showed stronger inhibitory effects against the two phytopathogens in vitro and improved plant resistance to pathogen infection after endophytic colonization. Transcriptomic analysis revealed that BbOCuV1 infection substantially remodeled the host’s metabolic network. Genes involved in amino acid metabolism, central carbon metabolism, and nitrogen metabolism were significantly upregulated. GO analyses revealed enrichment of transporter-related functions, whereas KEGG analysis showed that ABC transporter pathways were significantly affected, with 28 transporter-related genes upregulated (e. g. , BBA₀0005, BBA₀6725, and BBA₁0298) and 16 genes downregulated (e. g. , BBA₀3574, BBA₀3573, and BBA₀7777). These findings indicate that BbOCuV1 infection enhances its host’s physiological and antagonistic capacities by remodeling its metabolic network. This study expands the potential application of mycoviruses and EPFs, offering a novel strategy for biological control of crop diseases.
Guo et al. (Mon,) studied this question.