Characterization of South African Cryphonectria cubensis isolates infectedwith a C-parasitica hypovirus

Cryphonectria cubensis is the causal agent of a serious canker disease of E ucalyptus spp. in tropical and subtropical parts of the world. In this stud y, a South African C. cubensis isolate was transfected by electroporation w ith a synthetic RNA transcript corresponding to the full-length coding stra nd of the C. parasitica hypovirus (CHV1-EP713). Hypovirus infection resulte d in pronounced morphological changes that included a striking increase in bright yellow-orange pigment production, a reduction in mycelial growth rat e, and reduced sporulation. Greenhouse studies revealed that the virus-cont aining strain was significantly less virulent than the original virulent C. cubensis isolate. Although the hypovirus was not transmitted through conid ia produced by infected C. cubensis, the virus was readily transmitted via hyphal anastomosis to C. cubensis isolates representing a broad range of ve getative compatibility groups. These results suggest that vegetative incomp atibility may not pose a strong barrier against virus transmission in South African isolates of C. cubensis and that hypovirus-mediated biological con trol could provide opportunities to reduce the impact of Cryphonectria cank er in South Africa.