Identification and complete genome sequence of an alternavirus from a pathogenic fungus Fusarium nanum collected by air sampling

In this study, fungal spores were collected from the air, and mycelium was grown in petridishes containing potato dextrose agar medium in the lab. Based on the morphological and molecular characteristics, the fungus was identified as Fusarium nanum. A new double-stranded RNA (dsRNA) mycovirus was isolated from the mycelia of F. nanum and was tentatively named “Fusarium nanum alternavirus 1” (FnAV1). The complete genome sequence of FnAV1 was obtained by Illumina sequencing, followed by Sanger sequencing and the rapid amplification of cDNA ends (RACE) of 5′ and 3′-ends. FnAV1 is composed of three dsRNA segments: dsRNA1 (3546 nt) encodes RdRp, dsRNA2 (2511 nt) encodes a hypothetical protein, and dsRNA3 encodes the coat protein (2484 nt). The multiple alignments, along with phylogenetic analysis based on the RdRp (dsRNA1) and coat protein (dsRNA3) amino acid sequences, suggested that FnAV1 clustered with other members of the newly proposed family “Alternaviridae” and have high identities with Fusarium incarnatum alternavirus 1 (FiAV1), and might be a new strain isolated from a different fungal host, F. nanum. This is the first report of a mycovirus from the mycelial culture of F. nanum, which was obtained from spores collected at 39 ft altitude via air sampling. This suggests that the airborne spores could carry the mycovirus for long-distance movement and dissemination to new locations.