Diversity and horizontal gene transfer of mycoviruses in Exserohilum turcicum population from northern corn leaf blight of maize

Abstract Northern corn leaf blight, caused by Exserohilum turcicum , severely affects maize yields globally. Some mycoviruses induce host hypovirulence in phytopathogenic fungi, offering the potential for fungal biocontrol. To explore the diversity of mycoviruses and identify candidate hypovirulence-associated viruses in E. turcicum , we conducted high-throughput sequencing to analyze the virome of 60 isolates from maize-producing regions in Shanxi province, China. Bioinformatic analysis revealed 27 mycoviruses, including 13 novel viruses whose complete genome sequences were obtained through terminal cloning. These viruses belong to the families of Partitiviridae , Polymycoviridae , Hypoviridae , Fusariviridae , Endornaviridae , Mitoviridae , Botourmiaviridae , Mymonaviridae , Discoviridae , and unclassified viruses. Notably, a virus from the family Mymonaviridae has a bi-segmented genome, with its RNA1 segment encoding an additional small protein containing a Phytoreo_S7 domain homologous to chrysoviruses, suggesting horizontal gene transfer (HGT) between negative-stranded RNA viruses and double-stranded RNA viruses. We also observed the potential HGT of the Phytoreo_S7 domain between mycoviruses and fungi. Furthermore, virus curing via single conidial isolation of a slow-growing strain demonstrated that different viral combinations significantly influence host growth and pathogenicity. This study represents the first identification of highly diverse mycoviruses within E. turcicum , offering new insights into mycovirus diversity, evolution, and potential applications in the biocontrol of northern corn leaf blight.