Iftikhar R, Bag S, Ashfaq M, Pappu H R
National Institute of Biotechnology and Genetic Engineering, Faisalabad, Pakistan, and Department of Plant Pathology, Washington State University, Pullman, 99164.
Plant Dis. 2013 Nov;97(11):1517. doi: 10.1094/PDIS-05-13-0502-PDN.
Onion (Allium cepa L.) is an important vegetable crop in Pakistan. According to the Food and Agricultural Organization (FAO), Pakistan is the world's fifth largest onion producer. The area and production is 127.8 thousand hectares and 1.7 million tons, respectively, with a yield of 13.8 tons per hectare during 2012. The agro-ecological diversity in the country enables onion production almost year round. Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus), transmitted principally by Thrips tabaci, is an economically important viral pathogen of bulb and seed onion crops in many onion-growing areas of the world (1,3). In Asia, IYSV has been reported in India and Sri Lanka (2,4). During March to May 2012, as part of a survey for tospoviruses in vegetables, symptoms suspected to be caused by IYSV were observed on bulb and seed onions grown in farmers' fields in Faisalabad, Nankana, Sheikhupura, and Sialkot districts of Punjab. Symptoms consisted of spindle-shaped, straw colored, irregular chlorotic lesions with occasional green islands on the leaves. Approximately 60% of the fields surveyed had about 30% of the plants with these symptoms. The presence of the virus was confirmed with an IYSV-specific ELISA kit (Bioreba). IYSV infection was verified by RT-PCR with primers IYSV-F (TAAAACAAACATTCAAACAA) and IYSV-R (CTCTTAAACACATTTAACAAGCA) as forward and reverse primers, respectively. Amplicons of approximately 1,100 bp were obtained from the symptomatic samples, but not from healthy and water controls. The amplicons were cloned and sequenced. The IYSV-Pakistan isolates (GenBank Accession Nos. KF171103, KF171104, and KF171105) had the highest nucleotide sequence identity of 99% with the corresponding region of an IYSV isolate from Chile (DQ150107). To our knowledge, this is the first report of IYSV infecting onion in Pakistan. The relatively widespread occurrence of IYSV underscores the need for systematic surveys to assess its incidence and impact on onion bulb and seed crops so that appropriate management tactics can be developed. References: (1) D. H. Gent et al. Plant Dis. 88:446, 2004. (2) B. Mandal et al. Plant Dis. 94:468, 2012. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) K. S. Ravi et al. Plant Pathol. 55:288, 2006.
洋葱（葱属植物）是巴基斯坦一种重要的蔬菜作物。据联合国粮食及农业组织（粮农组织）称，巴基斯坦是世界第五大洋葱生产国。2012年，种植面积为12.78万公顷，产量为170万吨，每公顷产量为13.8吨。该国农业生态多样性使得洋葱几乎全年都能种植。鸢尾黄斑病毒（IYSV；布尼亚病毒科番茄斑萎病毒属）主要由西花蓟马传播，是世界许多洋葱种植区洋葱鳞茎和种子作物的一种具有经济重要性的病毒病原体（1,3）。在亚洲，印度和斯里兰卡已报道有IYSV（2,4）。2012年3月至5月期间，作为蔬菜中番茄斑萎病毒调查的一部分，在旁遮普省费萨拉巴德、南卡纳、谢赫普拉和锡亚尔科特地区农民田间种植的洋葱鳞茎和种子上观察到疑似由IYSV引起的症状。症状包括叶片上出现纺锤形、稻草色、不规则的褪绿病斑，偶尔有绿色小岛。大约60%的调查田块中约30%的植株有这些症状。使用IYSV特异性ELISA试剂盒（Bioreba）确认了病毒的存在。通过RT-PCR，分别以引物IYSV-F（TAAAACAAACATTCAAACAA）和IYSV-R（CTCTTAAACACATTTAACAAGCA）作为正向和反向引物，验证了IYSV感染。从有症状的样本中获得了约1100 bp的扩增子，但从健康样本和水对照中未获得。对扩增子进行了克隆和测序。巴基斯坦的IYSV分离株（GenBank登录号：KF171103、KF171104和KF171105）与来自智利的IYSV分离株（DQ150107）的相应区域的核苷酸序列同一性最高，为99%。据我们所知，这是IYSV在巴基斯坦感染洋葱的首次报道。IYSV相对广泛的发生凸显了进行系统调查以评估其发病率及其对洋葱鳞茎和种子作物影响的必要性，以便制定适当的管理策略。参考文献：（1）D. H. Gent等人，《植物病害》88:446，2004年。（2）B. Mandal等人，《植物病害》94:468，2012年。（3）H. R. Pappu等人，《病毒研究》141:219，2009年。（4）K. S. Ravi等人，《植物病理学》55:288，2006年。
