FIG MILD MOTTLE-ASSOCIATED VIRUS, A NOVEL CLOSTEROVIRUS INFECTING FIG

Abstract

The partial genome sequence of a putative new closterovirus with particles ca. 2000 nm long, denoted Fig mild mottle-associated virus (FMMaV), was determined. The 6,290 nt long sequence encompasses seven open reading frames (ORFs), i.e. an incomplete ORF1b encoding the putative RNA-dependent RNA polymerase (RdRp), a 25 kDa protein with unknown functions, a 6 kDa protein with putative nucleotide-binding properties, the 63 kDa homologue of the heat-shock protein 70 (HSP70h), a 64 kDa protein, the minor coat protein (CPm) of 26 kDa in size, and the incomplete coat protein (CP). The genome organization of FMMaV is the same as that of members of the genus Closterovirus. This taxonomic position was confirmed by comparative analyses of the RdRp, HSP70h and CPm amino acid sequences which clustered FMMaV in a clade comprising members of the genus Closterovirus in phylogenetic trees constructed with these sequences. Comparison with Fig leaf mottle-associated virus 1 (FLMaV-1), the other putative fig-infecting closterovirus currently known, showed ca. 30% divergence in the HSP70h gene at the amino acid level. In a preliminary survey carried out in southern Italian fig orchards, FMMaV was detected in three different cultivars.