Dokka Narasimham, Mahajan Mahesh Mohanrao, Sahu Bhimeshwari, Marathe Ashish, Singh Harvinder Kumar, Sivalingam Palaiyur Nanjappan
ICAR-National Institute of Biotic Stress Management, Baronda, Raipur, Chhattisgarh 493225, India.
Department of Plant Pathology, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh 492012, India.
Virus Res. 2021 Oct 2;303:198521. doi: 10.1016/j.virusres.2021.198521. Epub 2021 Jul 24.
Severe leaf curl disease of tomato (ToLCD) was noticed recently in the central parts of India and is an emerging threat to the cultivation of tomato. The genomic components of the begomovirus isolate, DNA A and betasatellite associated with ToLCD were cloned by rolling circle amplification method and sequenced. The sequence analysis revealed that the DNA A (2766 nt) of this isolate had the nucleotide identity of >91% with other strains of Tomato leaf curl Karnataka virus (ToLCKV), hence this isolate is proposed as a strain of ToLCKV, named as ToLCKV-Raipur. Similarly, the betasatellite molecule (1355 nt) had the highest identity of 91.1% with Corchorus yellow vein mosaic betasatellite (CoYVMB) and named as CoYVMB-Raipur. The full-length dimerized clones of these two genomic components were agroinoculated on natural (tomato), experimental (Nicotiana benthamiana) hosts and other 20 plant species belong to six different families. The severe leaf curl symptoms appeared only in the hosts, N. benthamiana, and in tomato inoculated with ToLCKV-Raipur alone and ToLCKV-Raipur with CoYVMB-Raipur after 8 and 16-18 days inoculation, respectively. This isolate was also transmissible to healthy tomato plants by whitefly from the tomato plant agroinoculated with ToLCKV-Raipur alone and with CoYVMB-Raipur and produced symptoms within 14-16 days after inoculation. Interestingly, this isolate infects horse gram and chilli by whitefly transmission and both the hosts showed positive for DNA A alone but not for betasatellite. Quantification of the genomic components of this isolate with the agroinoculated N. benthamiana samples by qRT-PCR results showed that the quantity of ToLCKV-Raipur was enhanced by three-fold while inoculated with CoYVMB-Raipur compared to ToLCKV-Raipur alone inoculated plants. However, CoYVMB-Raipur did not enhance the levels of ToLCKV-Raipur in the agroinoculated tomato plants. This is the first evidence of the natural co-occurrence of ToLCKV with betasatellite, CoYVMB causing ToLCD.
番茄严重卷叶病（ToLCD）最近在印度中部被发现，对番茄种植构成了新的威胁。通过滚环扩增法克隆了与ToLCD相关的双生病毒分离株的基因组成分DNA A和卫星DNA，并进行了测序。序列分析表明，该分离株的DNA A（2766 nt）与番茄卷叶卡纳塔克病毒（ToLCKV）的其他毒株具有>91%的核苷酸同一性，因此该分离株被提议作为ToLCKV的一个毒株，命名为ToLCKV-赖布尔。同样，卫星DNA分子（1355 nt）与黄麻黄脉花叶卫星DNA（CoYVMB）具有91.1%的最高同一性，命名为CoYVMB-赖布尔。将这两个基因组成分的全长二聚体克隆通过农杆菌介导接种到天然宿主（番茄）、实验宿主（本氏烟草）以及属于六个不同科的其他20种植物上。严重的卷叶症状仅在本氏烟草以及分别在接种ToLCKV-赖布尔8天后和接种ToLCKV-赖布尔与CoYVMB-赖布尔16 - 18天后的番茄中出现。该分离株也可通过烟粉虱从单独接种ToLCKV-赖布尔以及接种ToLCKV-赖布尔与CoYVMB-赖布尔的番茄植株传播到健康番茄植株上，并在接种后14 - 16天内产生症状。有趣的是，该分离株通过烟粉虱传播感染绿豆和辣椒，这两种宿主仅DNA A呈阳性，卫星DNA呈阴性。通过qRT-PCR对农杆菌介导接种的本氏烟草样本中该分离株的基因组成分进行定量分析，结果表明，与单独接种ToLCKV-赖布尔的植株相比，接种CoYVMB-赖布尔时ToLCKV-赖布尔的量增加了三倍。然而，CoYVMB-赖布尔并没有提高农杆菌介导接种的番茄植株中ToLCKV-赖布尔的水平。这是ToLCKV与卫星DNA CoYVMB自然共存导致ToLCD的首个证据。
