Abstract
Various mycoviruses have been isolated from Sclerotinia sclerotiorum. Here, we identified a viral RNA sequence contig, representing a novel virus, Sclerotinia sclerotiorum deltaflexivirus 2 (SsDFV2), from an RNA_Seq database. We found that SsDFV2 was harbored in the hypovirulent strain, 228, which grew slowly on potato dextrose agar, produced a few sclerotia, and could not induce typical lesions on detached rapeseed (Brassica napus) leaves. Strain 228 was also infected by Botrytis porri RNA Virus 1 (BpRV1), a virus originally isolated from Botrytis porri. The genome of SsDFV2 comprised 6711 nucleotides, excluding the poly (A) tail, and contained a single large predicted open reading frame encoding a putative viral RNA replicase. Phylogenetic analysis demonstrated that SsDFV2 is closely related to viruses in the family Deltaflexiviridae; however, it also differs significantly from members of this family, suggesting that it may represent a new species. Further we determined that SsDFV2 could be efficiently transmitted to host vegetative incompatible individuals by dual culture. To our best knowledge, this is the first report that a (+) ssRNA mycovirus can overcome the transmission limitations of the vegetative incompatibility system, a phenomenon that may facilitate the potential use of mycoviruses for the control of crop fungal diseases.
Highlights
Sclerotinia sclerotiorum (Lib.) de Bary, an ascomycetous fungus, is a devastating necrotrophic plant pathogen with wide host range that encompasses economically important crops, including vegetable crops, and is responsible for heavy global agricultural losses each year [1]
Sclerotinia sclerotiorum deltaflexivirus 2 (SsDFV2) is a member of the order Tymovirales
Phylogenetic analysis based on the entire replicase, methyltransferase, helicase, and RNA-dependent RNA Polymerase (RdRp) sequences of SsDFV2 demonstrated that it is closely related to the viruses SsDFV1, Soybean leaf-associated mycoflexivirus 1 (SlaMFV1), and FgDFV1, and could be tentatively assigned to the family Deltaflexiviridae
Summary
Sclerotinia sclerotiorum (Lib.) de Bary, an ascomycetous fungus, is a devastating necrotrophic plant pathogen with wide host range that encompasses economically important crops, including vegetable crops, and is responsible for heavy global agricultural losses each year [1]. The control of diseases caused by S. sclerotiorum depends mainly on chemical fungicides, since no resistant cultivars are available. It is important to explore novel, environmentally friendly alternatives to chemical fungicides or to reduce amounts of chemical fungicides used. Mycoviruses replicate in fungal cells and are widespread in nature. Some mycoviruses can confer hypovirulence to their hosts and, have potential as biological agents for disease control [2,3,4]. Mycoviruses can be transmitted vertically, via asexual reproduction
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