Exploring the potential of mycoviruses as new biological control agents (BCAs) against the grey mould fungus Botrytis cinerea

Botrytis cinerea is the fungus responsible for grey mould, a major disease affecting a wide range of host plants, both in the field and postharvest, leading to significant economic losses. Several mycoviruses are known to infect fungal plant pathogens, offering a potential new approach for biocontrol. In this study, we investigated the phylogenetic relationships of mycoviruses previously identified through a metagenomic analysis in B. cinerea, the presence of viruses putatively associated to host hypovirulence in individual isolates of the fungus, and their possible influence on the host phenotype. The analysis was performed on 11 (+)ssRNA viruses and revealed a great diversity and the phylogenetic relationships of the identified mycoviruses with known viruses within the Hypoviridae, Fusariviridae, and Mitoviridae families. The presence of eight viruses was checked by RT-PCR in 28 B. cinerea isolates, revealing single or multiple viral infections. Among the tested viruses, Botrytis cinerea mymonavirus 1 (BcMyV1) was selected for further analysis. Virus-free isogenic fungal lines were generated by antibiotic treatments combined with hyphal tipping. In vitro assays in virus-infected and virus-free isogenic lines revealed that BcMyV1 did not affect colony growth and spore germination. On artificially inoculated grape berries, a slightly reduced virulence of the virus-infected isolate compared to the virus-free isogenic lines was observed but this finding was not supported by statistical significance. The results obtained in this study contribute to the understanding of mycovirus diversity in B. cinerea and highlight the potential use of mycoviruses as new candidate biological control agents against grey mould.