The influence of Ophiostoma mitovirus-3a (OMV3a) on the respiration and growth of the dollar spot pathogen, Sclerotinia homoeocarpa (Bennett)

Sclerotinia homoeocarpa is the causal agent of dollar spot disease of turfgrass. Although both asymptomatic and hypovirulent isolates of S. homoeocarpa contain the mitochondrial virus Ophiostoma novo-ulmi mitovirus 3a (OMV3a), only asymptomatic isolates display growth rates and virulence levels comparable to that of virus-free isolates. In this study, the respiration and growth of asymptomatic, hypovirulent and virulent isolates of S. homoeocarpa were characterized using antimycin A (AA) as a complex III inhibitor, and salicylhydroxamic acid (SHAM) as an alternative oxidase inhibitor. Results of this study indicate that alternative oxidase contributes substantially to respiration by hypovirulent isolates. All S. homoeocarpa isolates appear to utilize the alternative pathway to some extent; however, hypovirulent isolates demonstrated a substantial increase in AOX transcription relative to asymptomatic and virulent isolates. These results demonstrate that OMV3a infection interferes with the normal function of mitochondria in S. homoeocarpa in hypovirulent isolates.