Mamoun Abdel-Salam Aly Mohamed, Rezk Adel A, Dawoud Rehab A
Pak J Biol Sci. 2019 Jan;22(2):83-94. doi: 10.3923/pjbs.2019.83.94.
Tomato Chlorosis Virus (ToCV) is a white fly-transmitted and phloem-limited crinivirus reported in this study for the first time in Egypt. ToCV caused drastic reduction in tomato yield since 2013. The aim of this study is to characterize the virus incidence using biological, serological and molecular tools.
The B. tabaci MEAM1 white fly was used for virus isolation and propagation. Identity of ToCV , its natural hosts were confirmed with RT-PCR using a specific primer pair for ToCV-heat shock protein 70 homologue (HSP70h) gene, sequencing and phylogenetic studies. ToCV was purified using the innovative electro-elution technique. The induced antiserum for the Egyptian isolate of the virus (ToCV-Giza) was used for DAS-ELISA and dot blotting immuno-assays to evaluate the virus presence in tomato and other natural hosts.
The ToCV-Giza isolate was donated an accession number "MH667315.1" from the GenBank. Blastx sequence analysis of the HSP70h gene indicated 97-99% of amino acid similarities with many tested ToCV isolates. Phylogenetic studies showed the clustering of all ToCV isolates including ToCV-Giza in a separate group from the other tested criniviruses. The virus had a UV spectrum of a nucleoprotein with Amax and Amin at 260 and 240 nm, respectively and A260/280 ratio of 1.33. Out of 52 different tested plant species within 22 families, 44 were positive hosts for ToCV. Thirty seven out of these 44 plant species were considered as new hosts for ToCV in the present study. These included Ammi majus and Coriandrum sativum (Apiaceae), cabbage (Brassicaceae), sweet potato (Convolvulaceae), melon, cucumber, luffa (Cucurbitaceae), soybean, cowpea, faba bean (Fabaceae), Egyptian and American Cotton (Malvaceae). Several ornamentals either herbal type or woody trees belonging to Acanthaceae, Amaranthaceae, Euophorbiaceae, Moraceae and Rubiaceae were also recognized for the first time as hosts for ToCV.
The obtained results confirmed the wide distribution of ToCV in its natural hosts in Egypt. Hygienic measures including control of the virus vector and removing of natural hosts should be strictly implicated.
番茄褪绿病毒（ToCV）是一种由烟粉虱传播、局限于韧皮部的长线形病毒，本研究首次在埃及报道。自2013年以来，ToCV导致番茄产量大幅下降。本研究的目的是利用生物学、血清学和分子工具对该病毒的发病率进行特征分析。
利用烟粉虱MEAM1分离和繁殖病毒。使用针对ToCV热休克蛋白70同源物（HSP70h）基因的特异性引物对，通过RT-PCR、测序和系统发育研究，确认ToCV及其天然寄主的身份。采用创新的电洗脱技术纯化ToCV。用该病毒埃及分离株（ToCV-Giza）诱导产生的抗血清进行双抗体夹心酶联免疫吸附测定（DAS-ELISA）和斑点印迹免疫分析，以评估番茄和其他天然寄主中病毒的存在情况。
ToCV-Giza分离株在GenBank中的登录号为“MH667315.1”。HSP70h基因的Blastx序列分析表明，与许多测试的ToCV分离株的氨基酸相似性为97%-99%。系统发育研究表明，包括ToCV-Giza在内的所有ToCV分离株都聚集在一个与其他测试长线形病毒不同的单独组中。该病毒的核蛋白紫外光谱显示，最大吸收峰（Amax）和最小吸收峰（Amin）分别在260和240nm处，A260/280比值为1.33。在22个科的52种不同测试植物中，44种是ToCV的阳性寄主。在本研究中，这44种植物中的37种被认为是ToCV的新寄主。其中包括大阿米芹和芫荽（伞形科）、甘蓝（十字花科）、甘薯（旋花科）、甜瓜、黄瓜、丝瓜（葫芦科）、大豆、豇豆、蚕豆（豆科）、埃及棉和美洲棉（锦葵科）。几种草本类型或木本树木的观赏植物，属于爵床科、苋科、大戟科、桑科和茜草科，也首次被确认为ToCV的寄主。
所得结果证实了ToCV在埃及天然寄主中的广泛分布。应严格采取包括控制病毒载体和清除天然寄主在内的卫生措施。
