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First Report of Tomato spotted wilt virus in Brugmansia suaveolens in Korea

Brugmansia suaveolens, also known as angel's trumpet, is a semi-woody shrub or a small tree. Because flowers of B. suaveolens are remarkably beautiful and sweetly fragrant, B. suaveolens is grown as ornamentals outdoors year-round in the tropics and subtropics, and as potted plants in temperate regions (1). In February 2013, virus-like symptoms including mosaic symptoms followed by distortion of leaves were observed in a potted B. suaveolens in a nursery in Chung-Nam Province, Korea. Symptomatic leaves were analyzed for the presence of several ornamental viruses including Cucumber mosaic virus (CMV), Tobacco mosaic virus (TMV), Tomato bush stunt virus (TBSV), and Tomato spotted wilt virus (TSWV) by immune-strip diagnostic kits that were developed by our laboratory. Positive controls and extract from healthy leaves of B. suaveolens as a negative control were included in each immune-strip assay. TSWV was detected serologically from the naturally infected B. suaveolens, but CMV, TBSV, and TMV were not detected from the B. suaveolens. The presence of TSWV (named TSWV-AT1) was confirmed by commercially available double-antibody sandwich (DAS)-ELISA kits (Agdia, Elkhart, IN). TSWV-AT1 was mechanically transmitted from the ELISA-positive B. suaveolens to Capsicum annuum and Nicotiana glutinosa, respectively. Inoculated C. annuum showed chlorotic rings in the inoculated leaves and inoculated N. glutinosa produced mosaic and systemic necrosis in the inoculated leaves after 7 days inoculation, respectively, which were consistent with symptoms caused by TSWV (2). To confirm further TSWV-AT1 infection, reverse transcription (RT)-PCR was performed using the One-Step RT-PCR (Invitrogen, Carlsbad, CA) with TSWV-specific primers, TSWV-NCP-For and TSWV-NCP-Rev (3), designed to amplify a 777-bp cDNA of the nucleocapsid protein (NCP) gene. Total RNAs from naturally infected B. suaveolens, symptomatic C. annuum, and N. glutinosa were extracted using RNeasy Plant Mini Kit (Qiagen, Valencia, CA). Total RNAs obtained from a Korean isolate of TSWV (Accession No. JF730744) and healthy B. suaveolens were used as positive and negative controls, respectively. The expected size of the RT-PCR product was amplified from symptomatic B. suaveolens, C. annuum, and N. glutinosa but not from healthy leaves of B. suaveolens. The amplified RT-PCR product from TSWV-AT1 was directly sequenced using BigDye Termination kit (Applied Biosystems, Foster City, CA). Multiple alignment of the TSWV-AT1 NCP sequence (AB910533) with NCP sequences of other TSWV isolates using MEGA5 software (4) revealed 99.0% aa identity with an Korean TSWV isolate (AEB33895) originating from tomato. These results provide additional confirmation of TSWV-AT1 infection. It is known that high-value ornamentals may act also as reservoirs for TSWV that can infect other ornamentals and cultivated crops, because TSWV has a very broad host range (2). Elaborate inspections for TSWV and other viruses are necessary for production of healthy B. suaveolens, since the popularity and economic importance of this ornamental plant is increasing. To our knowledge, this is the first report of TSWV in B. suaveolens in Korea.

References: (1) Anonymous. OEPP/EPPO Bull. 34:271, 2004. (2) G. Parrella et al. J. Plant Pathol. 85:227, 2003. (3) B.-N. Chung et al. Plant Pathol. J. 28:87, 2012. (4) K. Tamura et al. Mol. Biol. Evol. 28:2731, 2011.