Tsai W S, Shih S L, Lee L M, Wang J T, Duangsong U, Kenyon L
AVRDC - The World Vegetable Center, Shanhua, Tainan, 74151 Taiwan.
Research and Development in Agriculture Program, Kasetsart University, Nakhon Pathom 73140 Thailand.
Plant Dis. 2013 Feb;97(2):291. doi: 10.1094/PDIS-09-12-0847-PDN.
A disease of okra (Abelmoschus esculentus) causing yellowing veins and mosaic on leaves and fruit has emerged in Thailand. Incidences of 50 to 100% diseased plants were observed in fields in Kanchanaburi and Nakhon Pathom provinces in 2009 and 2010, respectively. Leaf samples were collected from three and four diseased plants in Kanchanaburi and Nakhon Pathom, respectively. All seven samples tested positive for begomovirus by PCR using universal primer pair PAL1v1978B/PAR1c715H (3). One sample from Kanchanaburi also tested positive by ELISA using Okra mosaic virus (Genus Tymovirus) antiserum (DSMZ, Braunschweig, Germany). When the nucleotide sequences of the 1.5 kb begomovirus PCR products were compared they were found to share 99.1 to 99.5% identity with each other, and 97.5 to 97.7% identity to Bhendi yellow vein mosaic virus Okra isolate from India (GenBank Accession No. GU112057; BYVMV-[IN: Kai:OY: 06]). The complete DNA-A sequence for a Kanchanaburi isolate (JX678967) was obtained using abutting primers WTHOK6FL-V/-C (WTHOK6FL-V: 5'-GCGAAGCTTAGATAACGCTCCTT-3'; WTHOK6FL-C: 5'-TCCAAGCTTTGAGTCTGCAACGT-3'), while that of a Nakhon Pathom isolate (JX678966) was obtained with primers WTHOK6FLV/WTHOK2FL-C (WTHOK2FL-C: 5'-TCCAAGCTTTGAGTCTGCATCGT-3'). The DNA-A sequences of both isolates are 2,740 nucleotides in length and share 99.6% identity. Each has the geminivirus conserved sequence (TAATATTAC), two open reading frames (ORFs) in the virus sense (V1 and V2) and four in the complementary sense (C1 to C4). Based on BLASTn searching GenBank and sequence analysis using MegAlign (DNASTAR), both DNA-A sequences have greatest nucleotide identity (96.2 to 96.4%) with BYVMV-[IN: Kai:OY: 06] from India. Also, BYVMV-associated betasatellite DNA (1.4 kb) was detected in all begomovirus-positive samples, except one sample from Nakhon Pathom (1). However, no virus DNA-B was detected in any of the samples using either general detection primer pair DNABLC1/DNABLV2 or DNABLC2/DNABLV2 (2). Okra infected with BYVMV has been reported in South Asia in Bangladesh, India, and Pakistan. To the best of our knowledge, this is the first report of BYVMV associated with Okra Yellow Vein Mosaic Disease in Southeast Asia. Since fruits with symptoms are regarded as low quality and have little market value, even low incidence of the disease is likely to cause significant reductions in marketable yield. Strategies for managing BYVMV in okra in South and Southeast Asia should be sought, including the breeding and selecting of resistant varieties. References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) S. K. Green et al. Plant Dis. 85:1286, 2001. (3) W. S. Tsai et al. Plant Pathol. 60:787, 2011.
泰国出现了一种秋葵（Abelmoschus esculentus）病害，导致叶片和果实出现叶脉黄化及花叶症状。2009年和2010年，北碧府和佛统府的田间分别观察到50%至100%的患病植株。分别从北碧府的3株和佛统府的4株患病植株上采集了叶片样本。使用通用引物对PAL1v1978B/PAR1c715H进行PCR检测，所有7个样本对双生病毒均呈阳性（3）。北碧府的一个样本使用秋葵花叶病毒（番茄病毒属）抗血清（德国不伦瑞克的德国微生物和细胞培养物保藏中心）进行ELISA检测也呈阳性。当比较1.5 kb双生病毒PCR产物的核苷酸序列时，发现它们彼此之间的同一性为99.1%至99.5%，与来自印度的黄秋葵黄脉花叶病毒秋葵分离株（GenBank登录号GU112057；BYVMV-[IN:Kai:OY:06]）的同一性为97.5%至97.7%。使用相邻引物WTHOK6FL-V/-C（WTHOK6FL-V：5'-GCGAAGCTTAGATAACGCTCCTT-3'；WTHOK6FL-C：5'-TCCAAGCTTTGAGTCTGCAACGT-3'）获得了北碧府分离株（JX678967）的完整DNA-A序列，而使用引物WTHOK6FLV/WTHOK2FL-C（WTHOK2FL-C：5'-TCCAAGCTTTGAGTCTGCATCGT-3'）获得了佛统府分离株（JX678966）的DNA-A序列。两个分离株的DNA-A序列长度均为2740个核苷酸，同一性为照99.6%。每个序列都有双生病毒保守序列（TAATATTAC），在病毒链上有两个开放阅读框（ORF）（V1和V2），在互补链上有四个开放阅读框（C1至C4）。基于在GenBank中进行的BLASTn搜索以及使用MegAlign（DNASTAR）进行的序列分析，两个DNA-A序列与来自印度的BYVMV-[IN:Kai:OY:06]的核苷酸同一性最高（96.2%至96.4%）。此外，在所有双生病毒阳性样本中均检测到了与BYVMV相关的β卫星DNA（1.4 kb），但佛统府的一个样本除外（1）。然而，使用通用检测引物对DNABLC1/DNABLV2或DNABLC2/DNABLV2（2）在任何样本中均未检测到病毒DNA-B。在南亚的孟加拉国、印度和巴基斯坦已报道秋葵感染了BYVMV。据我们所知，这是东南亚首次报道与秋葵黄脉花叶病相关的BYVMV。由于有症状的果实被视为低质量且市场价值不大，即使该病发病率较低也可能导致可销售产量大幅下降。应寻求在南亚和东南亚管理秋葵中BYVMV的策略，包括培育和选择抗性品种。参考文献：（1）R.W.布里登等，《分子生物技术》20：315，2002年。（2）S.K.格林等，《植物病害》85：1286，2001年。（3）W.S.蔡等，《植物病理学》60：787，2011年。
