Parrella G, Verdin E, Gognalons P, Marchoux G
Istituto per la Protezione delle Piante del CNR, Via Università 133, 80055 Portici (NA), Italy.
Commun Agric Appl Biol Sci. 2006;71(3 Pt B):1237-44.
During 2003 and 2004, unusual viral symptoms were observed on Surfinia trailing petunias in protected cultivations of Southern France. Symptoms consisted in yellow mosaic and distortion of the leaves accompanied by vein necrosis in some samples. The flowers were deformed and showed light colour break of the petals. Electron microscope observation of negatively stained leaf-dip from symptomatic leaves showed straight rod-shaped virus particles of about 300 nm in length. Sap extracts reacted in double-immunodiffusion tests by forming weak precipitin bands with antisera against Tomato mosaic virus (ToMV) and Tobacco mild green mosaic virus (TMGMV). However, symptoms developed on host range after mechanical inoculation suggested that ToMV was not involved in the disease. By using specific primer pairs designed to amplify the coat protein (CP) genes of ToMV and TMGMV in reverse transcriptase-polymerase chain reaction (RT-PCR), expected amplicon was obtained only with TMGMV primer pair. The identity of the virus was also confirmed by using a specific TMGMV riboprobe in dot-blot hybridization assays of symptomatic leaf extracts. The nucleotide sequence of TMGMV CP of the isolate from trailing petunia, named TMGMV-Pt, was determined and compared with those available from EMBL. The percentage of nucleotide identity was 97-98% compared with those of other isolates. Further molecular and biological characterization revealed that TMGMV-Pt belonging to the large type group of TMGMV isolates. In fact, the 3' UTR region of TMGMV-Pt consisted of 360 nucleotides, comprising of a 147 base repeat, as reported only for TMGMV large type isolates. Moreover, symptoms development observed on a differentially host range, used to distinguish between large type and small type isolates, confirmed that TMGMV-Pt belonging to the large type group of isolates. Only one commercial variety of trailing petunia out of 12 tested remained symptomless after mechanical inoculation with TMGMV-Pt. This highlights the potential risk that TMGMV could represent to petunia cultivations. To our knowledge this is the first report of a natural infection by TMGMV in trailing petunia.
2003年至2004年期间，在法国南部的保护地栽培中，人们观察到冲浪矮牵牛（Surfinia trailing petunia）出现了异常的病毒症状。症状表现为叶片出现黄色花叶和扭曲，部分样本伴有叶脉坏死。花朵变形，花瓣出现浅色断裂。对有症状叶片的负染叶浸出液进行电子显微镜观察，发现了长度约为300纳米的直杆状病毒粒子。汁液提取物在双向免疫扩散试验中与抗番茄花叶病毒（ToMV）和烟草轻度绿色花叶病毒（TMGMV）的抗血清形成了微弱的沉淀带。然而，机械接种后在寄主范围上出现的症状表明ToMV与该病无关。通过使用设计用于在逆转录聚合酶链反应（RT-PCR）中扩增ToMV和TMGMV外壳蛋白（CP）基因的特异性引物对，仅用TMGMV引物对获得了预期的扩增子。通过在有症状叶片提取物的斑点杂交试验中使用特异性TMGMV核糖探针，也证实了该病毒的身份。测定了来自垂吊矮牵牛的分离物（命名为TMGMV-Pt）的TMGMV CP的核苷酸序列，并与EMBL中可得的序列进行了比较。与其他分离物相比，核苷酸同一性百分比为97-98%。进一步的分子和生物学特性分析表明，TMGMV-Pt属于TMGMV分离物的大型组。事实上，TMGMV-Pt的3'UTR区域由360个核苷酸组成，包含一个147个碱基的重复序列，这仅在TMGMV大型分离物中报道过。此外，在用于区分大型和小型分离物的不同寄主范围上观察到的症状发展，证实了TMGMV-Pt属于大型分离物组。在12个测试的垂吊矮牵牛商业品种中，只有一个在机械接种TMGMV-Pt后仍无症状。这突出了TMGMV可能对矮牵牛栽培构成的潜在风险。据我们所知，这是TMGMV在垂吊矮牵牛中自然感染的首次报道。
