Molecular characterization of a novel fusarivirus infecting the plant-pathogenic fungus Neofusicoccum luteum.

Double-stranded RNAs from an isolate of Neofusicoccum luteum collected from grapevines were analyzed by high-throughput sequencing. Contig annotations revealed the presence of a potential novel virus belonging to the newly proposed family Fusariviridae. Completion of the viral genome sequence was performed. The genome is 6,244 nucleotide long, excluding the poly(A) tail and contains two putative open reading frames (ORFs). The first one encodes a large polypeptide of 1,552 amino acids (aa) with conserved RNA-dependent RNA polymerase and helicase domains typical of viral replicases. The second ORF encodes a putative 475-aa-long polypeptide showing weak homology to the corresponding ORF of Macrophomina phaseolina single-stranded RNA virus 1, for which no function is known so far. Phylogenetic analyses indicated that this virus should be considered a novel mycovirus belonging to the proposed family Fusariviridae, for which the name "Neofusicoccum luteum fusarivirus 1" (NlFV1) is proposed.

Determination of the complete genomic sequence of Neofusicoccum luteum mitovirus 1 (NLMV1), a novel mitovirus associated with a phytopathogenic Botryosphaeriaceae.

Neofusicoccum luteum species belongs to the Botryosphaeriaceae family and is involved in grapevine wood decay diseases. The present study reports the discovery and the molecular characterization of a novel mitovirus infecting this fungus. Double-stranded RNAs were purified from cultivated N. luteum and analysed by next generation sequencing. Using contigs showing BlastX homology with the RNA-dependent RNA polymerase (RdRp) gene of various members of the family Narnaviridae, a single contig of approximately 1.2 kb was constructed. The genomic sequence was completed and phylogenetic analyses indicated that this virus represents a new member of the genus Mitovirus, for which the name of "Neofusicoccum luteum mitovirus 1" is proposed. The genome is 2,389 nucleotides long and, based on the fungal mitochondrial genetic code, it encodes a putative protein of 710 amino acids, homologous to the RdRps of members of the Narnaviridae family. The neofusicoccum luteus mitovirus 1 (NLMV1) RdRp contains the six conserved motifs previously reported for mitoviral RdRps. Our findings represent the first evidence that a mycovirus can infect N. luteum, an important pathogenic fungus of grapevine.