Cryphonectria hypovirus 1 infection suppresses the pathogenicity but increases the mycotoxin deoxynivalenol production of Fusarium graminearum

Abstract Fusarium graminearum is a prominent pathogen responsible for causing head blight disease in small grain cereals, leading to substantial agricultural damage. A recent study revealed the infectivity of a hypovirus, Cryphonectria hypovirus 1 (CHV1), in F. graminearum . However, the effects of CHV1 on the pathogenicity and development of the fungus remain largely unexplored. In this study, we investigated the effects of CHV1 infection on F. graminearum and made several interesting discoveries. First, we observed that CHV1 infection attenuated the pathogenicity of F. graminearum and reduced its conidiation. CHV1 efficiently spread through various transmission modes, such as hyphal fusion and spores, including conidiospores and ascospores. However, the accumulation of the virus was reduced following transmission through spores. Interestingly, despite causing hypovirulence, CHV1 infection enhanced the production of deoxynivalenol (DON), a mycotoxin known to play a role in F. graminearum ’s virulence and induction of DON production by a DON-inducing medium elevated CHV1 accumulation. The transcriptional expression of key regulatory genes involved in DON biosynthesis or toxisome formation was upregulated in response to CHV1 infection. Furthermore, our study revealed that CHV1 infection suppressed the formation of lipid droplets. Overall, our study provides insights of how the infection of a hypovirulence-inducing mycovirus affects the physiological and metabolic processes in F. graminearum .