从湖南石门采集表现重花叶症状的马铃薯叶片中分离纯化到一株线状病毒HN021。经双链RNA(ds—RNA) 抽提、寄主反应测定、病毒粒子和内含体的形状观察， 初步确定该病毒为马铃薯x病毒(Potato virus x)。以 ds—RNA作为模板，用相应引物对HN021分离物的ORF4-UTR-ORF5片段进行RT—PCR，得到lkb左右的双链 cDNA片段。对该片段进行克隆和测序，并将测序所得的核苷酸序列与Genbank登录的11株不同分离物的相应 片段的核苷酸序列进行同源性比较和分析。结果表明，HN021与分离自南美洲的三株分离物(COAT，KPA 和 HB)的同源性为78-4％～79．4％，与其它8株(分离自亚洲、欧洲、大洋州和北美洲)分离物的同源性为96．4％一97．8％。 从氨基酸水平比较，HN021与COAT，KPA和HB三者CP和8kDa蛋白氨基酸序列同源性分别为86．5％～89．0％ 和74I3％～75．7％，相应地与其它8株分离物的同源性分别为97．1％一98．7％ 和97．1％一100％。序列分析的结果证实 了HN021分离物为马铃薯X病毒，同时表明PVX 明显存在两个组(组I和组II)，HN021和其它来自亚洲、欧 洲、大洋州、北美洲分离物的组II，3个南美洲分离物属于组I。

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