Alternaria spp. is a ubiquitous genus of fungi that includes a complex group of filamentous fungi, some of which cause significant damage across a wide range of crops [1]. Early blight, caused by Alternaria solani is an important foliar disease of potato worldwide. At present, many fungal viruses isolated and identified from Alternaria including Alternaria longipes dsRNA virus 1 (AlRV1) [4], Alternaria alternata chrysovirus 1 (AaCV1) [5], Alternaria alternata partitivirus 1 (AtPV1) [6], Alternaria dianthicola dsRNA virus 1 (AdRV1) [7], Alternaria arborescens victorivirus 1 (AaVV1) [8], Alternaria alternata hypovirus 1 (AaHV1) [9], Alternaria brassicicola fusarivirus 1(AbFV1) [10] etc. However, the isolation of fusarivirus from Alternaria solani has not been reported.
Mycoviruses, also called fungal viruses, are widespread in many simple eukaryotic organisms, such as yeasts, mushrooms, oomycetes and filamentous fungi, including phytopathogenic fungi [11–13]. The majority of fungal viruses typically exist as latent infections, but several mycoviruses can cause hypovirulence of their hosts, which are potential biocontrol agents to combat plant fungal disease [14–16]. Most fusariviruses infect their hosts without causing any morphological changes. However, several fusariviruses have phenotypic changes on their hosts, such as a 7.5kbp dsRNA branching virus isolated from Gramineae strain DK21, which is associated with fungal morphological changes. These include reduced mycelium growth, increased pigmentation, reduced virulence to wheat, and reduced (60-fold) production of trichothecene mycotoxins [25] .
The family Fusariviridae was proposed for encompassing the Fusarium graminearum virus-DK21 (FgV1) (the prototype of Fusariviridae) and other similar + ssRNA mycoviruses [17]. Up to date, the family Fusariviridae in NCBI database including Auricularia heimuer fusarivirus 1 (AhFV1), Nigrospora oryzae fusarivirus 1 (NoFV1), Alternaria brassicicola fusarivirus 1 (AbFV1), Botrytis cinerea fusarivirus 1 (BcFV1), Botryosphaeria dothidea fusarivirus 1 (BdFV1), Neofusicoccum luteum fusarivirus 1 (NlFV1), Sodiomyces alkalinus fusarivirus 1 (SaFV1), Rosellinia necatrix fusarivirus 1 (RnFV1), Sclerotinia sclerotiorum fusarivirus 1 (SsFV1), Fusarium graminearum dsRNA mycovirus-1 (FgV1), Pleospora typhicola fusarivirus 1 (PtFV1), Penicillium aurantiogriseum fusarivirus 1 (PaFV1), Macrophomina phaseolina single-stranded RNA virus 1 (MpRV1), Penicillium roqueforti ssRNA mycovirus 1 (PrRV1).The genomes of viruses in this family are + ssRNA, with sizes of 6–10 kb and one to three ORFs [18–19].
Here, we report the molecular characterization of a novel + ssRNA mycovirus Alternaria solani fusarivirus 1(AsFV1). Sequence analysis showed that AsFV1 is closely related to other putative fusariviruses. We suggest AsFV1 to be placed into the proposed family Fusariviridae.