Hypovirulence of Sclerotium rolfsii Caused by Associated RNA Mycovirus

Abstract

Mycoviruses associated with hypovirulence are potential biological control agents and could be useful to study the pathogenesis of fungal host pathogens. Sclerotium rolfsii, a pathogenic fungus, causes southern blight in a wide variety of crops. In this study, we isolated a series of dsRNAs from a debilitated S. rolfsii strain, BLH-1, which had pronounced phenotypic aberrations including reduced pathogenicity, mycelial growth and deficient sclerotia production. Virus-curing and horizontal transmission experiments that eliminated or transmitted, respectively, all dsRNA elements showed that the dsRNAs were involved in the hypovirulent traits of BLH-1. Ultrastructure examination also showed hyphae fracture and cytoplasm or organelle degeneration in BLH-1 hyphal cells compared to the virus-free strain. Three assembled cDNA contigs generated from the cDNA library cloned from the purified dsRNA indicated that strain BLH-1 was infected by at least three novel mycoviruses. One has similarity to the hypovirulence-associated Sclerotinia sclerotiorum hypovirus 2 (SsHV2) in the family Hypoviridae, and the other two are related to two different unclassified dsRNA mycovirus families. To our knowledge, this is the first report of S. rolfsii hypovirulence that was correlated with its associated dsRNA.

Laccase Activity in Fungus Cryphonectria parasitica Is Affected by Growth Conditions and Fungal–Viral Genotypic Interactions

“…It has been speculated that CHV1 s reductive effect on C. parasitica laccase is an important contributing factor for the reduction of fungal virulence [4]. Similar effects have been shown in phytopathogenic fungi Diaporthe ambigua, B. cinerea and Sclerotium rolfsii where mycoviruses have led to a hypovirulent effect and reduced LAC activity [42][43][44]. Interestingly, Cryphonectria hypovirus 3 also causes hypovirulence in C. parasitica, but without significant LAC reduction [45], while in hypovirulent B. cinerea infected with Botrytis cinerea mitovirus 1 increased LAC activity was reported [46].…”

Exploitation of Multifarious Abiotic Stresses, Antagonistic Activity and Plant Growth Promoting Attributes of Bacillus amyloliquefaciens AH53 for Sustainable Agriculture Production

“…In the present study strain AH53 was subjected for in-vitro antagonistic activity (dual-culture assay) against the fungal pathogens S. rolfsii and F. avenaceum. S. rolfsii is a versatile soilborne fungus plant pathogen which cause southern blight disease in broad host range of more than 600 species in tropical and subtropical regions (Zhong et al, 2016).…”

The PoV mycovirus affects extracellular enzyme expression and fruiting body yield in the oyster mushroom, Pleurotus ostreatus

“…Cryphonectria parasitica, B. cinerea, and S. rolfsii infected with CHV1, Bc378V1, and SsHV2, respectively, exhibited significantly reduced growth. Among representative extracellular enzymes, laccase activity is reduced in the mycovirus-infected strains because the laccase gene is one of several regulated genes affected by the presence of viral genes 4,23,24 . However, little is known about other factors associated with fungal-mycoviral interactions, even in industrially important fungi.…”