Center for Desert Agriculture, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Virol J. 2014 Jun 2;11:103. doi: 10.1186/1743-422X-11-103.
Tomato leaf curl Sudan virus (ToLCSDV) is a single-stranded DNA begomovirus of tomato that causes downward leaf curl, yellowing, and stunting. Leaf curl disease results in significant yield reduction in tomato crops in the Nile Basin. ToLCSDV symptoms resemble those caused by Tomato yellow leaf curl virus, a distinct and widespread begomovirus originating in the Middle East. In this study, tomato samples exhibiting leaf curl symptoms were collected from Gezira, Sudan. The associated viral genome was molecularly characterized, analyzed phylogenetically, and an infectious clone for one isolate was constructed.
The complete genomes for five newly discovered variants of ToLCSDV, ranging in size from 2765 to 2767-bp, were cloned and sequenced, and subjected to pairwise and phylogenetic analyses. Pairwise analysis indicated that the five Gezira isolates shared 97-100% nucleotide identity with each other. Further, these variants of ToLCSDV shared their highest nucleotide identity at 96-98%, 91-95%, 91-92%, and 91-92% with the Shambat, Gezira, Oman and Yemen strains of ToLCSDV, respectively. Based on the high maximum nucleotide identities shared between these ToLCSDV variants from Gezira and other previously recognized members of this taxonomic group, they are considered isolates of the Shambat strain of ToLCSDV. Analysis of the complete genome sequence for these new variants revealed that they were naturally occurring recombinants between two previously reported strains of ToLCSDV. Finally, a dimeric clone constructed from one representative ToLCSV genome from Gezira was shown to be infectious following inoculation to tomato and N. benthamiana plants.
Five new, naturally occurring recombinant begomovirus variants (>96% shared nt identity) were identified in tomato plants from Gezira in Sudan, and shown to be isolates of the Shambat strain of ToLCSDV. The cloned viral genome was infectious in N. benthamiana and tomato plants, and symptoms in tomato closely resembled those observed in field infected tomato plants, indicating the virus is the causal agent of the leaf curl disease. The symptoms that developed in tomato seedlings closely resembled those observed in field infected tomato plants, indicating that ToLCSDV is the causal agent of the leaf curl disease in Gezira.
番茄曲叶苏丹病毒（ToLCSDV）是一种单链 DNA 番茄曲叶病毒，可导致番茄叶片向下卷曲、变黄和生长受阻。尼罗河盆地的番茄作物因曲叶病而减产。ToLCSDV 的症状与番茄黄曲叶病毒相似，后者是一种起源于中东的独特而广泛存在的曲叶病毒。在这项研究中，从苏丹的杰济拉采集了表现出卷叶症状的番茄样本。对相关病毒基因组进行了分子特征分析、系统进化分析，并构建了一个分离株的传染性克隆。
克隆并测序了五个新发现的番茄曲叶苏丹病毒变异体的全长基因组，大小为 2765 至 2767bp，并进行了成对和系统进化分析。成对分析表明，杰济拉的五个分离株彼此之间的核苷酸同一性为 97-100%。此外，这些番茄曲叶苏丹病毒变异体与 Shambat、Gezira、阿曼和也门的 ToLCSDV 株的核苷酸同一性最高分别为 96-98%、91-95%、91-92%和 91-92%。基于这些来自杰济拉的 ToLCSDV 变异体与其他先前被认可的分类群成员之间的最大核苷酸同一性，它们被认为是 Shambat 株的分离株。对这些新变异体的全基因组序列分析表明，它们是两种先前报道的 ToLCSDV 株之间的自然重组体。最后，从杰济拉的一个代表性 ToLCSV 基因组构建的二聚体克隆在接种到番茄和 N. benthamiana 植物后显示出感染性。
在苏丹杰济拉的番茄植物中发现了五个新的自然发生的重组番茄曲叶病毒变异体（>96%的共享核苷酸同一性），并被鉴定为 Shambat 株的分离株。克隆的病毒基因组在 N. benthamiana 和番茄植物中具有感染性，番茄中出现的症状与田间受感染的番茄植物非常相似，表明该病毒是卷叶病的病原体。番茄幼苗中出现的症状与田间受感染的番茄植物非常相似，表明 ToLCSDV 是杰济拉卷叶病的病原体。
