Evidence for the assignment of two strains of SPLV to the genus Potyvirus based on coat protein and 3′ non-coding region sequence data

The use of potyvirus-specific primers and subsequent application of the RACE procedure allowed the cloning of the 3′ terminal 1088 nucleotides of the genomic RNA of the Taiwan isolate of sweetpotato latent virus (SPLV-T) and the 3′ genomic 1085 nucleotides of a SPLV-like virus from China (SPLV-CH). The sequence of an internal part of the presumptive nuclear inclusion b gene was also determined for both isolates. Detailed sequence analyses revealed the presence of consensus motifs which indicated that SPLV-CH and SPLV-T should be regarded as members of the genus Potyvirus. Multiple sequence alignments and phylogenetic analyses were also performed and unambiguously assessed these isolates as strains of a distinct Potyvirus. SPLV was not related to other potyviruses infecting sweetpotato nor to any other sequenced virus. From the presence of the DAG box, SPLV-CH is expected to be a typical aphid transmitted Potyvirus whereas a conceivable explanation is proposed for the non-aphid transmission of SPLV-T.