Hallan Vipin, Saxena Sangeeta, Singh B P
Plant Virus Laboratory, National Botanical Research Institute, Lucknow - 226 001 India.
Plant Dis. 1998 Jan;82(1):127. doi: 10.1094/PDIS.1998.82.1.127A.
Triumffeta rhomboidiaceae Jacq. (Tiliaceae family) is an annual rainy season weed that is commonly found throughout India. For the last 3 years, during the rainy season, several plants of T. rhomboidiaceae in and around the gardens of the National Botanical Research Institute have been found with vein yellowing symptoms. The initial symptoms were vein clearing but in later stages the veins became yellow and thickened. In severe cases, the chlorosis extends into interveinal areas, resulting in complete yellowing of the leaves. In a few cases, green leafy or thorny enations could be seen on the dorsal side of the leaf. The disease was investigated to identify the causal agent. Vector transmission studies showed that the causal agent is transmitted by the whitefly, Bemisia tabaci, from infected to healthy seedlings of T. rhomdoidiaceae. Since whitefly transmission of the disease is consistent with a geminivirus as the causal agent, the role of such a virus was investigated. DNA isolated from Triumffeta plants (both from the infected plants in the field as well as from those inoculated experimentally in the greenhouse) showing above mentioned symptoms was amplified with two sets of degenerate primers, PAL1v1978/PAR1c496 (set 1) and PAL1v1978/PCRc1 (set 2), that have been shown to be specific for DNA-A of whitefly transmitted geminiviruses (WTGs), in polymerase chain reaction (1). We could amplify DNA-A fragments of approximately 1.2 kb from set 1 and 0.7 kb from set 2, as expected (1). DNA isolated from healthy seedlings gave no amplification of such fragments. Identification of the amplified DNA fragments (from infected samples) to be of geminiviral in nature was confirmed by Southern blot hybridization carried out under high stringency conditions. DNA-A of Indian tomato leaf curl virus (2) was used as a general probe for WTGs for the above hybridization experiment. Therefore, Triumffeta yellow net disease is caused by a geminivirus. A review of literature revealed that there is no record of a viral disease affecting this weed and, therefore, this is the first report of a viral disease affecting this plant. References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) K. M. Srivastava et al. J. Virol. Methods 51:297, 1995.
菱叶刺蒴麻（Triumffeta rhomboidiaceae Jacq.，椴树科）是一种一年生雨季杂草，在印度各地普遍可见。在过去三年的雨季期间，国家植物学研究所园区内及周边的几株菱叶刺蒴麻出现了叶脉黄化症状。最初的症状是叶脉变清晰，但在后期叶脉变黄且变粗。在严重的情况下，黄化会扩展到叶脉间区域，导致叶片完全变黄。在少数情况下，叶片背面可见绿叶状或多刺的增生。对该病进行了调查以确定病原体。媒介传播研究表明，病原体是由烟粉虱（Bemisia tabaci）从受感染的菱叶刺蒴麻幼苗传播到健康幼苗。由于该病通过粉虱传播与双生病毒作为病原体相符，因此对这种病毒的作用进行了研究。从表现出上述症状的菱叶刺蒴麻植株（包括田间受感染植株以及温室中实验接种的植株）中分离的DNA，用两组简并引物PAL1v1978/PAR1c496（第1组）和PAL1v1978/PCRc1（第2组）进行扩增，这两组引物已被证明对粉虱传播双生病毒（WTGs）的DNA-A具有特异性，在聚合酶链反应中进行扩增（1）。正如预期的那样，我们从第1组中扩增出了约1.2 kb的DNA-A片段，从第2组中扩增出了0.7 kb的片段（1）。从健康幼苗中分离的DNA未扩增出此类片段。在高严谨条件下进行的Southern杂交证实了扩增的DNA片段（来自受感染样本）本质上是双生病毒的。印度番茄卷叶病毒（2）的DNA-A被用作上述杂交实验中WTGs的通用探针。因此，菱叶刺蒴麻黄网病是由一种双生病毒引起的。文献综述显示，没有关于影响这种杂草的病毒病的记录，因此，这是关于影响这种植物的病毒病的首次报道。参考文献：（1）M. R. Rojas等人，《植物病害》77:340，1993。（2）K. M. Srivastava等人，《病毒学方法杂志》51:297，1995。
