Naidu R A, Karthikeyan G, Jarugula S, Nelson M, Morrell A
Department of Plant Pathology, Washington State University-Irrigated Agriculture Research and Extension Center, Prosser 99350.
Northwest Horticulture, LLC, Mabton, WA 98935.
Plant Dis. 2008 Mar;92(3):486. doi: 10.1094/PDIS-92-3-0486B.
Perennial cultivars of Coreopsis, a genus native to the United States, are widely grown for aesthetics in home gardens and roadsides and are increasingly used in conservation projects and native-plant gardens. During the spring and summer of 2006 and 2007, Coreopsis auriculata 'Nana' plants with foliar symptoms showing chlorotic spots and rings were observed in wholesale and retail nurseries in Washington. Nicotiana benthamiana plants inoculated with crude sap extracts from symptomatic leaves of C. auriculata 'Nana' obtained from two different sources showed systemic mosaic mottling symptoms, indicating the presence of a virus. Symptomatic leaf samples from C. auriculata 'Nana' and N. benthamiana tested positive in antigen-coated plate-ELISA with potyvirus group-specific monoclonal antibodies (Agdia Inc., Elkhart, IN). Additional analysis by ELISA was positive for Lettuce mosaic virus (LMV; Agdia Inc.). To confirm these results, total RNA extracted from symptomatic N. benthamiana leaves was subjected to reverse transcription (RT)-PCR using potyvirus degenerate primers (PNIbF5: 5'-GCCAGCCCTCCACCGTNGTNGAYAA-3' and PCPR1: 5'-GGGGAGGTGCCGTTCTCDATRCACCA-3') covering the 3' end of the NIb gene and the 5' end of the CP gene (1). A single DNA band of approximately 1,000 bp amplified from symptomatic leaves of two independent plants was cloned separately into pCR2.1 (Invitrogen Corp., Carlsbad, CA). Two independent clones per amplicon were sequenced from both orientations. Pairwise comparison of these sequences with corresponding nucleotide sequences of potyviruses in GenBank showed 93 to 99% identity in the NIb/CP region with LMV sequences from France (GenBank Accession Nos. X97704, X65652, and X97705), China (GenBank Accession Nos. AJ306288 and AJ488153), and Brazil (GenBank Accession No. AJ278854). These results confirmed the presence of LMV in symptomatic leaves of N. benthamiana and C. auriculata 'Nana'. The occurrence of LMV has been reported in ornamental plants that included freeway daisy (Osteospermum fruticosum), lisianthus (Eustoma grandiflorum), and gazanias (Gazania spp.) (2-4). To our knowledge, this is the first documented evidence for the occurrence of LMV in Coreopsis, an economically important perennial ornamental widely grown in the United States. Although the origin of LMV in C. auriculata 'Nana' is not known, distribution of cuttings from LMV-infected C. auriculata 'Nana' plants to wholesale and retailers within Washington and across the country by movement of plant material could pose a risk to other ornamentals and crops like lettuce because of the broad host range of LMV and its potential transmission by several species of polyphagous aphids. Seed transmission as a potential means of dissemination of LMV in Coreopsis has not been examined, although the virus is seedborne in other plants such as lettuce. References: (1) Y.-C. Hsu et al. J. Virol. Methods 128:54, 2005. (2) V. Lisa et al. Inf. Fitopatol. 3:58, 1995. (3). D. C. Opgenorth et al Plant Dis. 75:751, 1991. (4) F. M. Zerbini et al. Plant Dis. 81:641, 1997.
金鸡菊属原产于美国，其多年生栽培品种在家庭花园和路边广泛种植以供观赏，并且越来越多地用于保护项目和原生植物园。在2006年和2007年的春夏季节，华盛顿的批发和零售苗圃中观察到了叶色有褪绿斑点和环纹症状的耳叶金鸡菊‘娜娜’植株。用从两个不同来源获得的耳叶金鸡菊‘娜娜’症状叶片的粗汁液提取物接种本氏烟草植株，出现了系统花叶斑驳症状，表明存在一种病毒。用马铃薯Y病毒属特异性单克隆抗体（Agdia公司，印第安纳州埃尔克哈特）进行的抗原包被板酶联免疫吸附测定（ELISA）显示，来自耳叶金鸡菊‘娜娜’和本氏烟草的症状叶片样本呈阳性。ELISA的进一步分析显示莴苣花叶病毒（LMV；Agdia公司）呈阳性。为了证实这些结果，从症状明显的本氏烟草叶片中提取的总RNA，使用覆盖NIb基因3′端和CP基因5′端的马铃薯Y病毒简并引物（PNIbF5：5′-GCCAGCCCTCCACCGTNGTNGAYAA-3′和PCPR1：5′-GGGGAGGTGCCGTTCTCDATRCACCA-3′）进行逆转录（RT）-PCR（1）。从两株独立植株的症状叶片中扩增出的约1000 bp的单一DNA条带分别克隆到pCR2.1（Invitrogen公司, 加利福尼亚州卡尔斯巴德）中。每个扩增子的两个独立克隆从两个方向进行测序。将这些序列与GenBank中马铃薯Y病毒的相应核苷酸序列进行成对比较，结果显示在NIb/CP区域与来自法国（GenBank登录号X97704、X65652和X97705）、中国（GenBank登录号AJ306288和AJ488153）以及巴西（GenBank登录号AJ278854）的LMV序列的同一性为93%至99%。这些结果证实了本氏烟草和耳叶金鸡菊‘娜娜’症状叶片中存在LMV。LMV在包括高速公路雏菊（蓝目菊）、洋桔梗和勋章菊等观赏植物中已有报道（2-4）。据我们所知，这是首次有文献记载LMV在耳叶金鸡菊中发生，耳叶金鸡菊是美国广泛种植的一种具有经济重要性的多年生观赏植物。虽然耳叶金鸡菊‘娜娜’中LMV的来源尚不清楚，但由于LMV的寄主范围广泛且可能由几种多食性蚜虫传播，感染LMV的耳叶金鸡菊‘娜娜’植株的插条通过植物材料的运输在华盛顿州内和全国各地的批发商和零售商之间流通，可能会对其他观赏植物和生菜等作物构成风险。尽管该病毒在生菜等其他植物中可通过种子传播，但尚未研究种子传播作为LMV在金鸡菊中传播的一种潜在方式。参考文献：（1）Y.-C. Hsu等人，《病毒学方法杂志》128:54，2005年。（2）V. Lisa等人，《植物病理学信息》3:58，
