Mycoviruses are viruses that infect fungi, and hypovirulence-associated mycoviruses have the potential to control fungal diseases. However, it is unclear how mycovirus-mediated hypovirulent strains live and survive in the field, and no mycovirus has been applied for field crop protection. In this study, we found that a previously identified small DNA mycovirus (SsHADV-1) can convert its host, Sclerotinia sclerotiorum, from a typical necrotrophic pathogen to a beneficial endophytic fungus. SsHADV-1 downregulates the expression of key pathogenicity factor genes in S. sclerotiorum during infection. When growing in rapeseed, the SsHADV-1-infected strain DT-8 significantly regulates the expression of rapeseed genes involved in defense, hormone signaling, and circadian rhythm pathways. As a result, plant growth is promoted and disease resistance is enhanced. Field experiments showed that spraying DT-8 at the early flowering stage can reduce the disease severity of rapeseed stem rot by 67.6% and improve yield by 14.9%. Moreover, we discovered that SsHADV-1 could also infect other S. sclerotiorum strains on DT-8-inoculated plants and that DT-8 could be recovered from dead plants. These findings suggest that the mycoviruses may have the ability to shape the origin of endophytism. Our discoveries suggest that mycoviruses may influence the origin of endophytism and may also offer a novel strategy for disease control in which mycovirus-infected strains are used to improve crop health and release mycoviruses into the field.

真菌病毒是感染真菌的病毒，低毒力相关的真菌病毒具有控制真菌疾病的潜力。然而，目前尚不清楚真菌病毒介导的低毒株如何在田间生存和存活，也没有真菌病毒应用于田间作物保护。在这项研究中，我们发现先前鉴定的小 DNA 真菌病毒 (SsHADV-1) 可以将其宿主核盘菌从典型的坏死性病原体转变为有益的内生真菌。SsHADV-1下调的关键致病因子基因的表达小号。菌核感染期间。在油菜籽中生长时，受 SsHADV-1 感染的菌株 DT-8 显着调节了与防御、激素信号传导和昼夜节律通路相关的油菜籽基因的表达。结果，促进植物生长并增强抗病性。田间试验表明，在开花初期喷施DT-8可使油菜茎腐病病害减轻67.6%，增产14.9%。此外，我们发现 SsHADV-1 也可以感染其他S。菌核DT-8 接种植物上的菌株，并且可以从死亡植物中回收 DT-8。这些发现表明真菌病毒可能具有塑造内生菌起源的能力。我们的发现表明，真菌病毒可能影响内生菌的起源，也可能为疾病控制提供一种新策略，其中使用感染真菌病毒的菌株来改善作物健康并将真菌病毒释放到田间。