A novel partitivirus confers dual contradictory effects to its host fungus: growth attenuation and virulence enhancement

Here, we identified a novel partitivirus, tentatively named Sinodiscula camellicola partitivirus 1 (ScPV1), marking the first report of a partitivirus from a phytopathogenic fungus infecting tea plants. ScPV1 is characterized by possession of two dsRNA genomic components encapsidated in particles of varying sizes, along with an RNA-dependent RNA polymerase protein of an expected size, which contained some unique amino acids, indicating its distinct molecular and morphological traits. Biological tests on transfectants generated following protoplast infection with purified virions demonstrated that ScPV1 impairs vegetative growth while enhancing virulence in its fungal host. This finding represents the first instance of a mycovirus responsible for hypervirulence on a phytopathogenic fungus through virion transfection, as well as the first case of a partitivirus conferring hypervirulence while reducing vegetative growth in a phytopathogenic fungus. We anticipate that these findings will significantly advance our understanding of the complex interactions between mycoviruses and their host fungi.