Saxena Sangeeta, Hallan Vipin, Singh B P, Sane P V
Plant Virus Laboratory, National Botanical Research Institute, Lucknow - 226 001, India.
Plant Dis. 1998 Jan;82(1):126. doi: 10.1094/PDIS.1998.82.1.126A.
Papaya has considerable economic importance to agriculture in India. Papaya leaf curl disease was first reported in 1939 by Thomas and Krishnaswamy (3). This disease is of moderate incidence and widely distributed in India. Recent observations of papaya fields in India indicated that there has been a continued increase in the incidence of papaya leaf curl disease (as shown by symptoms), resulting in severe economic losses. The disease is characterized by downward curling and cupping of leaves followed by vein clearing and thickening. Enations develop in the form of frills on green veins. The affected leaves become leathery and brittle and the petioles become twisted in a zig-zag manner. Diseased plants may bear a few small fruits, which are distorted in shape and tend to fall prematurely. The disease could be transmitted by the whitefly Bemisia tabaci Genn. Therefore, possible involvement of a geminivirus was suspected. Three different cloned geminiviral DNAs, Indian tomato leaf curl virus (ITLCV) (2), tomato yellow leaf curl virus from Sardinia (TYLCV Sar), and tomato golden mosaic virus (TGMV), were used as probes (with radioactive labeling) to detect the presence of geminiviral DNA from infected papaya tissue in both slot-blot and Southern blot hybridization studies with high stringency washes. These DNA probes gave strong signals with DNA isolated from infected papaya tissue whereas they did not give any signals with DNA from healthy tissue. Further, successful polymerase chain reaction (PCR)-based amplification of fragments from both DNA-A and DNA-B components with geminivirus degenerate primers (1) was accomplished only from the DNA of infected papaya plants. The PCR-amplified DNA fragments gave positive signals in Southern blot hybridization with the three geminiviral DNA probes. These results suggest that the causal agent of papaya leaf curl disease is a bipartite geminivirus that may be provisionally called papaya leaf curl virus (PLCV). References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) K. M. Srivastava et al. J. Virol. Methods 51:297, 1995. (3) K. M. Thomas and C. S. Krishnaswamy. Curr. Sci. 8:316, 1939.
番木瓜对印度农业具有相当重要的经济意义。番木瓜叶卷曲病于1939年由托马斯和克里希纳斯瓦米首次报道（3）。这种病害发病率中等，在印度广泛分布。最近对印度番木瓜种植园的观察表明，番木瓜叶卷曲病的发病率持续上升（从症状可见），造成了严重的经济损失。该病的特征是叶片向下卷曲和杯状卷曲，随后叶脉变清晰和增粗。在绿色叶脉上以褶边的形式形成耳突。受感染的叶片变得坚韧且易碎，叶柄呈之字形扭曲。患病植株可能结少数小果实，果实形状扭曲且往往过早掉落。该病可由烟粉虱传播。因此，怀疑可能有双生病毒参与其中。在狭缝印迹和Southern印迹杂交研究中，使用三种不同的克隆双生病毒DNA，即印度番茄叶卷曲病毒（ITLCV）（2）、来自撒丁岛的番茄黄叶卷曲病毒（TYLCV Sar）和番茄金色花叶病毒（TGMV）作为探针（进行放射性标记），以检测受感染番木瓜组织中双生病毒DNA的存在，并进行高严谨度洗涤。这些DNA探针与从受感染番木瓜组织中分离的DNA产生强信号，而与健康组织的DNA不产生任何信号。此外，仅从受感染番木瓜植株的DNA中，使用双生病毒简并引物（1）成功地基于聚合酶链反应（PCR）扩增了DNA - A和DNA - B组分的片段。PCR扩增的DNA片段在与三种双生病毒DNA探针的Southern印迹杂交中产生阳性信号。这些结果表明，番木瓜叶卷曲病的病原是一种双分体双生病毒，可暂称为番木瓜叶卷曲病毒（PLCV）。参考文献：（1）M. R. 罗哈斯等人，《植物病害》77:340，1993年。（2）K. M. 斯里瓦斯塔瓦等人，《病毒学方法杂志》51:297，1995年。（3）K. M. 托马斯和C. S. 克里希纳斯瓦米，《当前科学》8:316，1939年。
