Bag S, Rogers P, Watson R, Pappu H R
Department of Plant Pathology, Washington State University, Pullman 99164.
Nunhems USA, 8850 59th Ave NE, Brooks, OR 97305.
Plant Dis. 2009 Aug;93(8):839. doi: 10.1094/PDIS-93-8-0839A.
Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is an important constraint to onion bulb and seed production in several onion-growing regions of the United States (1,3). While garlic (Allium sativum) was reported to be infected with IYSV in Réunion Island (4), there have been no confirmed reports of natural infection of garlic in the United States. Garlic plants showing near-diamond-shaped lesions were found in August of 2008 in Marion County, Oregon. The 0.4046-ha (1-acre) field plot consisted of various true-seeded garlic varieties and was adjacent to three onion fields that showed IYSV symptoms. Symptoms were observed on 5% of the garlic plants with most of the symptomatic plants displaying small and diffuse straw-colored spots. Seven of these symptomatic plants were selected for testing. Of these, two showed characteristic diamond-shaped, elongated, straw-colored lesions on garlic scapes. However, the lesions were more diffuse with less-defined edges compared with the characteristic diamond-shaped lesions that are often associated with IYSV infection (1). All symptomatic plants were positive for IYSV by double-antibody sandwich-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). To verify IYSV infection, total nucleic acid extracts from the symptomatic parts of the leaves were prepared and tested for the presence of IYSV by reverse transcription (RT)-PCR with primers 5'-TAAAACAAACATTCAAACAA-3' and 5'-CTCTTAAACACATTTAACAAGCAC-3', which flank the nucleocapsid (N) gene coded by the small RNA of IYSV (2). An approximate 1.1-kb amplicon was obtained from all symptomatic plants and cloned and sequenced. Nucleotide sequence comparisons using BLAST showed that a consensus of three clones derived from the amplicon from garlic (No. FJ514257) was 85 to 99% identical with IYSV sequences available in GenBank (Nos. AF001387, AB180918, and AB286063), confirming the identity of IYSV. To our knowledge, this is the first report of natural infection of IYSV infection of garlic in the United States. Additional surveys and testing are needed to obtain a better understanding of IYSV incidence in garlic to evaluate its impact on garlic production. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) I. Robène-Soustrade et al. Plant Pathol. 55:288, 2006.
鸢尾黄斑病毒（IYSV；布尼亚病毒科番茄斑萎病毒属）是美国几个洋葱种植区洋葱鳞茎和种子生产的重要限制因素（1,3）。虽然据报道留尼汪岛上的大蒜（葱属）感染了IYSV（4），但在美国尚无大蒜自然感染的确切报道。2008年8月，在俄勒冈州马里恩县发现了有近似菱形病斑的大蒜植株。这块0.4046公顷（1英亩）的田地种植了各种实生大蒜品种，毗邻三块有IYSV症状的洋葱田。在5%的大蒜植株上观察到症状，大多数有症状的植株表现为小而分散的稻草色斑点。从这些有症状的植株中挑选了七株进行检测。其中，两株在蒜薹上表现出典型的菱形、细长、稻草色病斑。然而，与通常与IYSV感染相关的典型菱形病斑相比，这些病斑更分散，边缘更不清晰（1）。使用市售试剂盒（Agdia公司，印第安纳州埃尔克哈特）通过双抗体夹心ELISA检测，所有有症状的植株IYSV均呈阳性。为了验证IYSV感染，制备了叶片有症状部位的总核酸提取物，并使用引物5'-TAAAACAAACATTCAAACAA-3'和5'-CTCTTAAACACATTTAACAAGCAC-3'通过逆转录（RT）-PCR检测IYSV的存在，这两个引物位于IYSV小RNA编码的核衣壳（N）基因两侧（2）。从所有有症状的植株中获得了一个约1.1 kb的扩增子，并进行了克隆和测序。使用BLAST进行核苷酸序列比较表明，来自大蒜扩增子（编号FJ514257）的三个克隆的共识序列与GenBank中可用的IYSV序列（编号AF001387、AB180918和AB286063）的同一性为85%至99%，证实了IYSV的身份。据我们所知，这是美国大蒜IYSV自然感染的首次报道。需要进行更多的调查和检测，以更好地了解大蒜中IYSV的发病率，评估其对大蒜生产的影响。参考文献：（1）D. Gent等人，《植物病害》90:1468，2006年。（2）H. R. Pappu等人，《病毒学档案》151:1015，2006年。（3）H. R. Pappu等人，《病毒研究》141:219，2009年。（4）I. Robène-Soustrade等人，《植物病理学》55:288，2006年。
