A Novel Ourmia-Like Mycovirus Confers Hypovirulence-Associated Traits on Fusarium oxysporum

Abstract

Fusarium wilt caused by <i>Fusarium oxysporum</i> f. sp. <i>momordicae</i> (<i>FoM</i>) is an important fungal disease that affects the production of bitter gourd. Hypovirulence-associated mycoviruses have great potential and application prospects for controlling the fungal disease. In this study, a novel ourmia-like virus, named <i>Fusarium oxysporum</i> ourmia-like virus 1 (FoOuLV1), was isolated from <i>FoM</i> strain HuN8. The viral genomic RNA is 2,712 nucleotides (nt) in length and contains an open reading frame (ORF) encoding a putative RNA-dependent RNA polymerase (RdRp) using either standard or mitochondrial codes. In strain HuN8, there was also a FoOuLV1-associated RNA segment with 1,173 nt in length with no sequence homology. Phylogenetic analysis showed that FoOuLV1 is a member of the genus <i>Magoulivirus</i> of the family <i>Botourmiaviridae</i>. FoOuLV1 was found to be associated with hypovirulence in <i>FoM</i>. Moreover, FoOuLV1 and its hypovirulence trait can be transmitted horizontally to other <i>FoM</i> strains and also to other formae speciale strains of <i>F. oxysporum</i>. In addition, FoOuLV1 showed significant biological control effect against the bitter gourd Fusarium wilt. To our knowledge, this study reveals the first description of a hypovirulence-associated ourmia-like mycovirus, which has the potential to the biological control of Fusarium wilt.