Hoepting C A, Fuchs M F
Cornell Cooperative Extension Vegetable Program, 12690 Route 31, Albion, NY 14411.
Plant Dis. 2012 Aug;96(8):1229. doi: 10.1094/PDIS-03-12-0254-PDN.
Iris yellow spot virus (IYSV; genus Tospovirus; family Bunyaviridae) is an economically important pathogen of onion. It is vectored by onion thrips (Thrips tabaci Lindeman) and causes widespread disease of onion in all major onion growing states in the western United States (1). In the eastern United States, IYSV was first reported in Georgia in 2004 (4) and then in New York in 2006 (2). In mid-July of 2010, symptomatic onion (Allium cepa) plants (cv. Candy) were found in New Holland, Pennsylvania, in Lancaster County on a small, diversified commercial farm (40.06°N, 76.06°W). Bleached, elongated lesions with tapered ends occurred on middle-aged leaves on approximately 30% of the 13,760 plants in an area approximately one tenth of an acre. Leaf tissue from five symptomatic plants tested positive for IYSV in a double-antibody sandwich (DAS)-ELISA with IYSV-specific serological reagents from Agdia Inc. (Elkhart, IN). A reverse transcription (RT)-PCR assay was used to verify the presence of IYSV in a subset of symptomatic leaf samples that reacted to IYSV antibodies in DAS-ELISA. Primers specific to the nucleocapsid (N) gene of IYSV (5'-ACTCACCAATGTCTTCAAC-3' and 5'-GGCTTCCTCTGGTAAGTGC-3') were used to characterize a 402-bp fragment (3). The resulting amplicons were ligated in TOPO TA cloning vector (Invitrogen, Carlsbad, CA) and two clones of each isolate were sequenced in both directions. Sequence analysis showed a consensus sequence for the partial N gene of the five IYSV isolates from Pennsylvania (GenBank Accession No. JQ952568) and an 87 to 100% nucleotide sequence identity with other IYSV N gene sequences that are available in GenBank. The highest nucleotide sequence identity (100%) was with an IYSV isolate from Texas (GenBank Accession No. DQ658242) and the lowest was with an isolate from India (GenBank Accession No. EU310291). To our knowledge, this is the first report of IYSV infection of onion in Pennsylvania. This finding confirms further spread of the virus within North America. Further study is warranted to determine the impact of IYSV on the Pennsylvania onion industry and to determine viable management strategies, if necessary. References: (1) D. H. Gent et al. Plant Dis. 88:446, 2004 (2) C. A. Hoepting et al. Plant Dis. 91:327, 2007 (3) C. L. Hsu et al. Plant Dis. 95:735-743. (4) S. W. Mullis et al. Plant Dis. 88: 1285, 2004.
鸢尾黄斑病毒（IYSV；番茄斑萎病毒属；布尼亚病毒科）是一种对洋葱具有重要经济影响的病原体。它由葱蓟马（西花蓟马）传播，在美国西部所有主要洋葱种植州引发了广泛的洋葱病害（1）。在美国东部，IYSV于2004年首次在佐治亚州被报道（4），随后于2006年在纽约被报道（2）。2010年7月中旬，在宾夕法尼亚州兰开斯特县的新荷兰一个小型多元化商业农场（北纬40.06°，西经76.06°）发现了有症状的洋葱（Allium cepa）植株（品种为Candy）。在约十分之一英亩面积的13760株植株中，约30%的中年叶片上出现了带有渐细末端的漂白、细长病斑。使用来自Agdia公司（印第安纳州埃尔克哈特）的IYSV特异性血清学试剂，通过双抗体夹心（DAS）-ELISA检测，来自五株有症状植株的叶片组织对IYSV呈阳性反应。采用逆转录（RT）-PCR检测法，对在DAS-ELISA中与IYSV抗体发生反应的一部分有症状叶片样本进行检测，以验证IYSV的存在。使用针对IYSV核衣壳（N）基因的特异性引物（5'-ACTCACCAATGTCTTCAAC-3'和5'-GGCTTCCTCTGGTAAGTGC-3'）来扩增一个402碱基对的片段（3）。将得到的扩增产物连接到TOPO TA克隆载体（Invitrogen公司，加利福尼亚州卡尔斯巴德）中，并对每个分离株的两个克隆进行双向测序。序列分析显示，来自宾夕法尼亚州的五个IYSV分离株的部分N基因共有一个一致序列（GenBank登录号JQ952568），与GenBank中其他IYSV N基因序列的核苷酸序列同一性为87%至100%。核苷酸序列同一性最高（100%）的是来自得克萨斯州的一个IYSV分离株（GenBank登录号DQ658242），最低的是来自印度的一个分离株（GenBank登录号EU310291）。据我们所知，这是宾夕法尼亚州洋葱感染IYSV的首次报道。这一发现证实了该病毒在北美地区的进一步传播。有必要进一步开展研究，以确定IYSV对宾夕法尼亚州洋葱产业的影响，并确定可行的管理策略（如有必要）。参考文献：（1）D. H. Gent等人，《植物病害》88:446，2004年 （2）C. A. Hoepting等人，《植物病害》91:327，2007年 （3）C. L. Hsu等人，《植物病害》95:735 - 743。（4）S. W. Mullis等人，《植物病害》88: 1285，2004年。
