Work

First detection, symptoms and management of Southern tomato virus in the United Kingdom

Year: 2021

Type: article

Abstract: In May 2018, tomato leaves (Solanum lycopersicum cv. Delisher) exhibiting symptoms of necrotic patches were collected from a glasshouse in Southern England. It was suspected that the samples were infected with Tomato chlorosis virus (ToCV), genus Crinivirus, as ToCV had been detected in a different variety on the same holding. Analysis was done by high throughput sequencing (Fox et al., 2019). The presence of ToCV could not be confirmed. A total of 3,453,344 reads were produced from the sample and 652 were found to represent the complete genome sequence of Southern tomato virus (STV), genus Amalgavirus (GenBank Accession No. MW266062) with an average coverage of 34 and with 100% nucleotide sequence identity to the original isolate of STV discovered in 2009 (EF442780.1). To confirm the presence of this virus, a specific real-time RT-PCR for STV (Table 1) was designed using PRIMER EXPRESS v.2 (Life Technologies Co., USA). The sample tested positive using this assay. During 2018, three tomato samples, cv. Dometica, from two different locations in northern England, with symptoms of severe leaf mottling and veinal necrosis (Fig. 1) had also been submitted to Fera Science Ltd. The samples tested negative by ELISA for common tomato viruses: Tomato mosaic virus, Tomato spotted wilt virus, Potyvirus (DSMZ, Germany); Alfalfa mosaic virus, Impatiens necrotic spot virus, Pepino mosaic virus, Potato virus Y, (Bioreba, Switzerland); Cucumber mosaic virus (Agdia, USA); and Potato virus X (Fera Science Ltd., UK). The samples also tested negative by PCR for Tomato torrado virus (Verbeek et al., 2012) and pospiviroids (Botermans et al., 2020). Mechanical inoculation to Chenopodium quinoa, Nicotiana benthamiana, N. hesperis, N. occidentalis P1 and Solanum lycopersicum) did not result in symptoms 21 days post inoculation. The samples were stored at -80°C. In 2019 samples were reanalysed using the STV real-time RT-PCR (Table 1), all samples tested positive. Seeds linked to the two northern outbreaks were also tested using the assay and found to be positive. STV, first detected in USA and Mexico (Sabanadzovic et al., 2009) has since been reported in several countries in Europe and Asia (Oh et al., 2018.). STV has been reported to be associated with mottling, yellowing and/or chlorotic spotting (Gaafar et al., 2019), this report records the virus as also being associated with veinal necrosis. Similar symptoms were observed in glasshouses across England, sporadically in 2018–9 and STV was subsequently detected. A further variety (cv. Lewis) was found to be co-infected with Pepino mosaic virus. STV has been detected from different tomato varieties in the UK. No management action is recommended in England or Wales unless symptoms are severe or STV is found in combination with other viruses. This work was supported by Defra under its Plant Health Long-Term Service Agreement with Fera Science Ltd.

Source: New Disease Reports

DOI: 10.1002/ndr2.12014