Citrus tristeza virus (CTV) causes economically important losses to the citrus industry worldwide. Mild strain crossprotection (MSCP) against tristeza has hardly been practised due to mixed infection of different CTV-strains and littlebackground of its molecular biology in China. For better cognition on CTV, 192 sweet orange samples collected from eightprovinces (Chongqing, Sichuan, Fujian, Hunan, Guangxi, Yunnan, Guangdong and Jiangxi) were tested by direct tissueblot immuno-assay (DTBIA), and 158 of them were tested positively, which therefore were subjected to coat protein gene(CPG)/HinfⅠrestriction fragment length polymorphism (RFLP) analysis. Sample bulks were compared between Chongqingand Fujian by some statistical data, including ratios of single infection and mixed infection to local samples, proportionsof CTV isolates with single RFLP groups, and rates of each RFLP group. The simplified analysis of samples from the othersix provinces were then conducted. This study suggests that CTV isolates with CPG/Hinf Ⅰ RFLP groups Ⅲ and Ⅰ arethe main epidemic ones in China, and mixed infection of CTV in fields are popular. Based on observation of severity ofstem-pitting symptom in field trees, CTV isolates with CPG/Hinf Ⅰ RFLP groups Ⅲ and Ⅰ caused severe stem-pittingsin sweet oranges in China.
对4种柑橘衰退病毒源及其31个单蚜传毒分离株的CP基因做了限制性片段长度多态性(RFLP)和单链构象多态性(SSCP)分析,并对其中8个单蚜传毒分离株的CP基因进行了序列分析。实验明确了所研究柑橘衰退病毒(Citrus triste-za virus,CTV)的CPG/Hinf I RFLP组群和CPG/SSCP模式,二者能较好地对应并有效验证了单蚜传毒对CTV毒源的分离纯化作用;CP基因序列分析结果表明,相同CPG/Hinf I RFLP组群的单蚜传毒分离株间具有高度的序列相似性,而不同CPG/Hinf I RFLP组群单蚜传毒分离株间则存在较大差异;通过与已知生物学特性CTV分离株比较,初步建立了上述CP基因分子特征与病毒生物学特性之间的联系。
应用限制性片段长度多态性（RFLP）、双向逆转录-聚合酶链式反应（BD-PCR）、序列分析等技术对我国部分地区柑橘衰退病毒（Citrus tristeza virus，CTV）柚类分离株进行了鉴定分析。结果表明：柚类以受相对单一的CTV株系侵染为主；柚类上的优势流行株系属于p25／Hin f ⅠRFLP6组群（占79．4％）和p23／BD-PCRⅢ组群（占84．1％）；在对柚类CTV分离株S051～S058及国外CTV分离株PB61、T30、T36、T385、SY568、VT、NUAGA的p23、p25基因序列分析中，S051与弱毒株PB61的同源性最高；S052与弱毒株T30、T385的同源性最高；S053、S054、S055、S056、S057、S058与其它CTV分离株的同源关系均较远，并在系统发生树上形成了独立的分枝。
为研究不同柑橘类型对柑橘衰退病病毒构成的影响,将9个保存在新会橙上的引起甜橙茎陷点症状的柑橘衰退病毒强毒分离株嫁接接种到凤凰柚后,比较了接种前后p25基因的Hinf I RFLP和SSCP变化情况。分离株CT90与CT20接种前后的RFLP组群没有发生变化;RFLP组群发生变化的分离株中有6个由混合组群变为单一组群。此外,除分离株CT90接种前后的SSCP谱带保持不变外,其余8个分离株从新会橙接种到凤凰柚后,SSCP谱带数均呈减少趋势。试验结果倾向于表明某些能在甜橙上增殖的CTV株系在凤凰柚上的增殖受到了抑制。
