A dsRNA mycovirus causes hypovirulence of Fusarium graminearum to wheat and maize

The association of Fusarium graminearum isolate China-9 with the dsRNA mycovirus FgV-ch9 was evaluated for hypovirulence-related traits. Single conidia-originating cultures of China-9 isolate can be associated either with high, medium or low amounts of the viral dsRNAs. At high and medium dsRNA levels, China-9 isolates exhibit reduced mycelia growth rate and conidiation capacity, abnormal colony morphology, disorganized cytoplasm, as well as reduced virulence for wheat and maize plants. At low dsRNA levels the fungus shows no symptoms, however, the RNA segments can be detected by RT-PCR. Transfection of the virulent F. graminearum PH-1 isolate with purified Virus-like Particles (VLPs) of FgV-ch9 reduced its conidiation capacity, perithecia formation, and pathogenicity for wheat and maize several folds. These results further demonstrate that FgV-ch9 is associated with hypovirulence of F. graminearum.