Identification and Grouping Study of Potato virus X Hunan Isolate

A filamentous virus HN021 was isolated and purified from mosaic leaves of Solanum tuberosum collected from Shimen, Hunan province. It was primarily identified as potato virus X by double-stranded RNA analysis, host reaction tests and morphological observation of virus particles and inclusions. A fragment of about 1kb size was obtained by RT-PCR, which was performed with ds-RNA as template of cDNA synthesis and respective primers designed for 3’ end sequence of PVX. Homological comparison was carried out between the nucleotide sequences of ORF4-UTR-ORF5 regions of HN021 and those of 11 PVX isolates submitted to Genbank. Our result showed that HN021 was 78.4%-79.4% identical to three isolates from South America (COAT, KPA and HB), whereas up to 96.4%-97.8% identical to other eight isolates. From the comparison of sequences of amino acids, the similarities of CP and 8kDa protein were 86.5%-89.0% and 74.3%-75.5% respectively between HN021 and the three isolates from South America, and were 97.1%-98.7% and 97.1%-1