Gawande S J, Khar A, Lawande K E
Directorate of Onion and Garlic Research, Rajgurunagar, Pune, India.
Plant Dis. 2010 Aug;94(8):1066. doi: 10.1094/PDIS-94-8-1066C.
Garlic (Allium sativum) is a spice crop of prime importance in India as well as other parts of the world. Iris yellow spot virus (IYSV; genus Tospovirus, family Bunyaviridae) is an important pathogen of onion bulb and seed crops in many parts of the world (3). The virus is also known to infect garlic and other Allium spp. (2-4). IYSV infection of garlic was reported from Reunion Island (4) and the United States (1). In February 2010, straw-colored, spindle-shaped spots with poorly defined ends were observed on the leaves of a garlic crop at the research farm of the Directorate of Onion and Garlic Research in the Pune District of Maharashtra State, India, 105 days after planting. The spots coalesced to form larger patches on the leaves, suggesting possible IYSV infection. Symptoms were visible on older leaves and more prevalent on cv. G-41, G-282, AC50, AC200, AC283, and Godavari than on other cultivars. The incidence of symptomatic plants was estimated at 5% for G-41 and AC-200, 8% for G-282 and AC283, and 10% for AC50. Leaves were sampled from 40 symptomatic plants per cultivar with each sample composited from young, middle, and older (basal) leaves of the plant. Samples were assayed by double-antibody sandwich-ELISA (Loewe Biochemica GmbH, Sauerlach, Germany) and each tested positive for the virus. Total RNA was extracted from the leaves of ELISA-positive plants using the RNAeasy Plant Mini kit (Qiagen GmbH, Hilden, Germany) and tested by reverse transcription-PCR assay using primers IYSV-F (5'-TCAGAAATCGAGAAACTT-3') and IYSV-R (5'-TAATTATATCTATCTTTCTTGG-3') (2) designed to amplify 797 bp of the nucleocapsid (N) gene of IYSV. Amplicons of expected size were obtained and cloned into a pDrive vector (Qiagen GmbH). The recombinant clone was sequenced (GenBank Accession No. HM173691). Sequence comparisons showed 98 to 100% nt identity with other IYSV N gene sequences in GenBank (Nos. EU310294 and EU310286). A phylogenetic analysis of the deduced amino acid sequences of the N gene showed that the garlic isolate of IYSV grouped most closely with onion IYSV isolates from India (GenBank Nos. EU310294, EU310286, EU310300, and EU310296). To our knowledge, this is the first report of natural infection of garlic by IYSV in India. Additional surveys and evaluations are needed to obtain a better understanding of the potential impact of IYSV on garlic production in India. References: (1) S. Bag et al. Plant Dis. 93:839, 2009. (2) A. Bulajic et al. Plant Dis. 93:976, 2009. (3) D. Gent et al. Plant Dis. 90:1468, 2006. (4) I. Robène-Soustrade et al. Plant Pathol. 55:288, 2006.
大蒜（Allium sativum）是一种在印度以及世界其他地区都极为重要的香料作物。鸢尾黄斑病毒（IYSV；番茄斑萎病毒属，布尼亚病毒科）是世界许多地区洋葱鳞茎和种子作物的重要病原体（3）。已知该病毒也会感染大蒜和其他葱属植物（2 - 4）。留尼汪岛（4）和美国（1）曾报道过大蒜感染IYSV的情况。2010年2月，在印度马哈拉施特拉邦浦那区洋葱和大蒜研究局的试验农场，种植105天后，在大蒜作物的叶片上观察到稻草色、纺锤形的斑点，斑点两端界限不清。这些斑点在叶片上合并形成更大的斑块，表明可能感染了IYSV。症状在老叶上可见，在品种G - 41、G - 282、AC50、AC200、AC283和戈达瓦里上比其他品种更普遍。G - 41和AC - 200的感病植株发生率估计为5%，G - 282和AC283为8%，AC50为10%。从每个品种的40株感病植株上采集叶片，每个样本由植株的幼叶、中叶和老（基部）叶混合组成。样本通过双抗体夹心ELISA（德国洛伊生物化学有限公司）进行检测，每个样本均检测出病毒呈阳性。使用RNAeasy植物微型试剂盒（德国希尔德市Qiagen有限公司）从ELISA阳性植株的叶片中提取总RNA，并使用引物IYSV - F（5'-TCAGAAATCGAGAAACTT-3'）和IYSV - R（5'-TAATTATATCTATCTTTCTTGG-3'）（2）通过逆转录PCR检测进行检测，这些引物旨在扩增IYSV核衣壳（N）基因的797 bp片段。获得了预期大小的扩增子，并将其克隆到pDrive载体（德国希尔德市Qiagen有限公司）中。对重组克隆进行了测序（GenBank登录号HM173691）。序列比较显示与GenBank中其他IYSV N基因序列（登录号EU310294和EU310286）的核苷酸同一性为98%至100%。对N基因推导的氨基酸序列进行系统发育分析表明，大蒜IYSV分离株与来自印度的洋葱IYSV分离株（GenBank登录号EU310294、EU310286、EU310300和EU310296）的亲缘关系最为密切。据我们所知，这是印度关于大蒜被IYSV自然感染的首次报道。需要进行更多的调查和评估，以更好地了解IYSV对印度大蒜生产的潜在影响。参考文献：（1）S. Bag等人，《植物病害》93:839，2009年。（2）A. Bulajic等人，《植物病害》93:976，2009年。（3）D. Gent等人，《植物病害》90:1468，2006年。（4）I. Robène - Soustrade等人，《植物病理学》55:288，2006年。
