Unveiling the hidden virome of Sclerotinia sclerotiorum: New tools and discoveries in mycovirus detection.

Mycoviruses are widespread in fungi and can influence fungal physiology, pathogenicity, and ecological interactions. In the plant pathogenic fungus Sclerotinia sclerotiorum, increasing attention has been directed toward understanding the diversity and functional roles of its associated viruses. This review synthesizes current knowledge on mycovirus detection methods and summarizes the diversity of viruses reported in S. sclerotiorum. Early detection strategies based on double-stranded RNA profiling, virion purification, and RT-PCR laid the foundation for mycovirus discovery but were limited in their ability to detect low-abundance or highly divergent viruses. The emergence of next-generation sequencing (NGS) and metatranscriptomic approaches has transformed the field, enabling large-scale in silico mining of fungal transcriptomes and facilitating the discovery of numerous novel viruses. To date, more than 270 mycoviruses have been reported from S. sclerotiorum, spanning over 30 viral families and representing diverse genome types. Many of these viruses occur in mixed infections and some are associated with hypovirulence, a phenotype characterized by reduced fungal growth and pathogenicity that holds potential for biological control. Despite rapid advances in virus discovery, significant gaps remain in understanding the functional consequences of infection, transmission dynamics, and ecological interactions within fungal populations. Integrating classical molecular techniques with high-throughput sequencing and functional studies will be essential for translating mycoviral diversity into mechanistic insights and applied strategies for disease management.