Columnea latent viroid (CLVd) in tomato: the first report in the United Kingdom

In May 2007 a tomato plant (Lycopersicum esculentum) cv. Santa from a glasshouse crop in northwest England was submitted to the Central Science Laboratory (now Fera). Symptoms included severe leaf distortion, bronzing and ‘crunchy’ leaf (Fig. 1). ELISA tests for Tomato spotted wilt virus, Impatiens necrotic spot virus, Pepino mosaic virus and Tomato mosaic virus were negative and examination by electron microscopy revealed no virus particles. The sample was tested for viroids using a new Scorpion real-time PCR test developed at CSL (unpublished data), designed to detect all pospiviroids. The sample tested positive for Columnea latent viroid (CLVd) and negative for other pospiviroids. The sample was also tested by conventional RT-PCR, using primers to detect a broad range of pospiviroids (Verhoeven et al., 2004). A product of the expected size (350bp) was obtained and confirmed to be CLVd by nucleotide sequence comparison (99% nt identity) (GenBank Accession No. FJ394071).

CLVd has since been confirmed at three further sites in cv. Santa: one in the same stock at the initial outbreak site, but in a different location; one in northeast England (FJ394070) and another in Worcestershire (FJ394072). CLVd sequence data were identical from all three sampling sites. Since the intraspecific variation for all CLVd sequences is 8.22% (GenBank) this suggests that the four UK outbreaks have a common source.

CLVd has previously been found in tomatoes in the Netherlands and Belgium (Verhoeven et al., 2004) but CLVd had not been previously recorded in the UK. At one site it was estimated that by the end of the growing season (November 2007), 50-60% of the crop was infected. Initial assessments at CSL suggested that CLVd posed a threat to tomato and possibly potato production in the UK. Statutory plant health action was immediately taken to control the outbreaks and by the end of the 2008 cropping season, CLVd was declared eradicated from the UK.