Mycoviruses as Biocontrol Agents: Potential Applications for Managing Pests and Diseases of Oilseed Rape (Brassica napus).

Oilseed rape (Brassica napus) production faces a wide range of biotic threats. Pests typically pose a greater threat than diseases to oilseed rape, yet both vary considerably across the major cultivating regions. Management strategies often rely heavily on the use of chemical pesticides which may have harmful effects on the environment, thus developing new forms of biological control is key to future oilseed rape security. Mycoviruses are viruses that infect fungi, altering phenotypes of their host upon infection and are emerging as potential biocontrol agents. In plant pathogenic fungi, mycovirus-induced hypovirulence can be used to reduce disease severity and in entomopathogenic fungi (EPF), mycovirus-induced hypervirulence can enhance effectiveness of EPF-based pest control. Mycoviruses of some pathogenic fungi, like Sclerotinia sclerotiorum, have been explored extensively and present many candidates for biocontrol. Viral diversity of other pathogenic fungi remains poorly understood and therefore presents an opportunity for new discoveries. In this review, we summarise existing mycoviruses of pathogenic fungi relevant to oilseed rape, highlighting those species with potential to control their respective pests/diseases. Furthermore, recent advancements in mycovirus research and the current challenges facing mycovirus-based applications are also discussed.