First report of Tomato chlorotic dwarf viroid infecting commercial Petunia stocks in the United Kingdom

Following findings of Potato spindle tuber viroid (PSTVd) in Solanaceous ornamental plants (e.g. Solanum jasminoides, Brugmansia suaveolans.) and the adoption of EC emergency measures, in 2007 Member States of the European Union were required to carry out a survey of host plants for the presence of PSTVd. In Scotland, as part of this survey, a total of 166 samples of Petunia were taken from 5 commercial nurseries. Each sample consisted of one leaflet from each of ten plants. At the time of sampling there were no disease symptoms.

Primary screening used a general PSTVd DIG-labelled probe that also hybridises to other pospiviroids (EPPO, 2004). A total of 13 varieties from two suppliers, one in Israel and the other in Portugal, were found to be positive for the presence of a pospiviroid. Positive samples from these varieties were then re-tested by RT-PCR using the PSTVd primers of Weidemann & Buchta (1998) and yielded PCR products of 359 bp (full length). The PCR products were sequenced and used for identification.

One full length nucleotide sequence from each Petunia supplier was submitted to Genbank (Accession numbers EF582392 and EF582393) and found to be 99.4 and 99.7% identical, respectively, to Tomato chlorotic dwarf viroid (TCDVd) sequence (Genbank Accession DQ859013). TCDVd was confirmed in the remaining 11 samples by Blast similarity searches using partial sequence information i.e. sequences were not full-length, double-stranded.

To our knowledge, this is the first report of TCDVd in commercial stocks of Petunia. The viroid has previously been intercepted in the Netherlands in quarantined Petunia material from the United States of America (Verhoeven et al., 2007) and has also been reported in tomatoes (Singh et al., 1999). The infected Petunia stocks were destroyed.