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Brugmansia suaveolens, known as angel's trumpet, is a perennial ornamental shrub in the Solanaceae with large fragrant flowers. In June 2018, a leaf sample of B. suaveolens that showed virus-like symptoms including chlorotic spots, yellowing and mottle on leaves was collected from a greenhouse in Seongnam, South Korea for disease diagnosis (Supplementary Figure S1a, b). Disease incidence in the greenhouse was greater than 80% for about 2,000 B. suaveolens plants. To identify a causal virus, transmission electron microscopy (TEM) was used to analyze symptomatic leaf samples using leaf dips and thin section methods. Filamentous virus particles and pinwheel structures were observed, indicating the presence of a potyvirus (Supplementary Figure S1c, d). To confirm the TEM results, a symptomatic leaf sample was further analyzed by reverse-transcription polymerase chain reaction (RT-PCR) using species-specific detection primers for three potyviruses that infect Brugmansia spp.: Colombian datura virus (CDV), Brugmansia mosaic virus (BruMV), and Brugmansia suaveolens mottle virus (BsMoV) (Lucinda et al, 2008; Park et al., 2014; Verma et al., 2014). The sample was positive only for CDV. CDV is transmitted by aphids in a nonpersistent manner and mechanical inoculation and can infect plants in the Solanaceae family including tomato and tobacco (Kahn and Bartels 1968; Schubert et al. 2006; Verhoeven et al. 1996) and has been designated a quarantine virus in Korea. Additional analysis of 13 symptomatic B. suaveolens plants from the infected greenhouse found that all samples except one were infected with CDV. To isolate CDV from B. suaveolens, leaf extracts from symptomatic samples were mechanically inoculated on an assay host, Nicotiana tabacum cv. BY via three single-lesion passages followed by propagation in N. benthamiana. For the bioassay of the CDV isolate (CDV-AT-Kr), sap from infected N. benthamiana was mechanically inoculated on 31 indicator plants, including B. suaveolens (Supplementary Table S2). CDV-AT-Kr induced chlorotic local lesions, necrotic local lesions, mottle, and/or mosaic systemically in 10 Nicotiana spp., and mottle and yellowing in tomato. On inoculated B. suaveolens, te mild mottle symptom was reproduced. No symptoms were observed in pepper or Datura stramonium. These results were confirmed by RT-PCR. To characterize CDV-AT-Kr genetically, the complete genome sequence of CDV-AT-Kr was obtained by RT-PCR using specific primers (Supplementary Table S3) and deposited in GenBank (accession no. MW075268). The CDV-AT-Kr RNA consists of 9,620 nt, encoding a polyprotein of 3,076 aa. BLASTn analysis showed that CDV-AT had maximum nucleotide identities of 98.9% at the complete genome level with a CDV isolate (accession no. JQ801448) from N. tabacum in the UK. To our knowledge, this is the first report of CDV infection in B. suaveolens in Korea and the second report in the world of the complete genome sequence. As B. suaveolens is cultivated by vegetative propagation, production and maintenance of virus-free, healthy B. suaveolens is needed. In addition, as new CDV hosts have been repeatedly reported (Pacifico et al., 2016; Salamon et al., 2015; Tomitaka et al., 2014; Verma et al., 2014), we are monitoring nationwide occurrence to prevent the spread of the virus to other crops. |
