A negative-strand RNA virus, VmNSRV1, was identified in the phytopathogenic fungus Valsa mali, which infects apple trees in Shaanxi Province, China. This virus, related to the family Phenuviridae, induces hypovirulence in the fungus and was found to infect both the fungus and plants. VmNSRV1 was detected in 24 out of 139 apple trees tested, indicating its prevalence in the natural environment. The virus can be transmitted between apple plants and V. mali, and infection in plants reduces the development of fungal lesions on leaves. The nucleocapsid protein of VmNSRV1 is associated with rearranged lipid droplets in both fungal and plant cells. VmNSRV1 represents a virus that has adapted to both plant and fungal hosts and can shuttle between these two organisms in nature, making it a potential biocontrol agent for plant fungal diseases. This finding expands the understanding of virus evolution and adaptation across plant and fungal hosts. VmNSRV1 is a novel virus that can infect both plants and fungi, suggesting that cross-kingdom infections are more common than previously thought. The virus's ability to infect both hosts and its potential for biocontrol highlight its significance in plant pathology and virology. The study provides insights into the mechanisms of cross-kingdom viral transmission and the adaptation of viruses to different host systems.A negative-strand RNA virus, VmNSRV1, was identified in the phytopathogenic fungus Valsa mali, which infects apple trees in Shaanxi Province, China. This virus, related to the family Phenuviridae, induces hypovirulence in the fungus and was found to infect both the fungus and plants. VmNSRV1 was detected in 24 out of 139 apple trees tested, indicating its prevalence in the natural environment. The virus can be transmitted between apple plants and V. mali, and infection in plants reduces the development of fungal lesions on leaves. The nucleocapsid protein of VmNSRV1 is associated with rearranged lipid droplets in both fungal and plant cells. VmNSRV1 represents a virus that has adapted to both plant and fungal hosts and can shuttle between these two organisms in nature, making it a potential biocontrol agent for plant fungal diseases. This finding expands the understanding of virus evolution and adaptation across plant and fungal hosts. VmNSRV1 is a novel virus that can infect both plants and fungi, suggesting that cross-kingdom infections are more common than previously thought. The virus's ability to infect both hosts and its potential for biocontrol highlight its significance in plant pathology and virology. The study provides insights into the mechanisms of cross-kingdom viral transmission and the adaptation of viruses to different host systems.