中文摘要：

采用RT-PCR获得黄瓜花叶病毒CMV-CB7株系全长基因组cDNA,经克隆测序发现该CMV的RNA1、2和3分别为3356nt、3045nt和2218nt（序列登录号为：EF216866、DQ785470和EF216867）.CMV-CB7基因组cDNA克隆体外转录RNA接种心叶烟引起坏死症状,而CMV-Fny则产生典型花叶.由CMV-CB7和CMV-Fny基因组RNA相互交换而构建6个假重组型病毒（C1C2F3、C1F2C3、F1C2C3、F1F2C3、F1C2F3和C1F2C3）活性分析表明：CMV-CB7基因组RNA2决定其在寄主上的症状反应.嵌合型RNA2（RNA2F5C3和RNA2C3F5）的寄主侵染活性测定表明：2b基因或RNA23′端非编码序列决定CMV-CB7在心叶烟坏死症状.RNA印迹分析结果显示：CMV-CB7和CMV-FnyF5C3引起寄主坏死与基因组RNA积累没有直接关系.

英文摘要：

Full length cDNAs of Cucumber mosaic virus （CMV） CB7 strain, causing necrosis on Nicotiana glutinosa, were obtained by RT-PCR, using viral genomic RNAs as templates, cDNAs of CMV-CB7 genomic RNAs were cloned and sequenced and results indicated that RNA1, 2 and 3 was 3 356 nt, 3 045 nt and 2 218 nt, respectively （accordingly Accession Number EF216866, DQ785470 and EF216867）. Infectious RNA transcripts from cDNA clones of CMV-CB7 were inoculated onto N. glutinosa and the seedlings of host plants displayed necrosis symptom, whist that of CMV-Fny induced typical mosaic symptoms. Through pseudorecombination between CMV-CB7 and CMV-Fny genomic RNAs, the genetic determinant of necrosis phenotype was mapped to RNA2. Chimeric infectious clones consisting of partial sequences of RNA2 derived from CMV-CB7 and CMV-Fny, respectively, were obtained by Overlapping PCR. Pathogenic analysis with those chimeric RNA2 revealed that 2b gene or 3＇ UTR of CMV-CB7 RNA2 was responsible for the necrotic pathotype. Northern blotting analysis reflected that both necrotic and non-necrotic viruses accumulated to similar levels of genomic RNAs in host plants. Therefore, necrotic phenotype induced on N. glutinosa was not related to the level of accumulation of CMV genomic RNAs.