First report of Columnea latent viroid on tomatoes in the United Kingdom
In England (GB), 4 outbreaks of Columnea latent viroid (Pospiviroid, CLVd) were confirmed in nurseries producing tomatoes (Lycopersicon esculentum) in December 2007. Phytosanitary measures are being implemented to contain the outbreaks and eradicate the disease. This was the first time that CLVd has been reported in the United Kindgom.
CLVd was originally isolated from symptomless Columnea erythrophaea (Gesneriaceae, originating from Central America and cultivated for ornamental purposes), during experiments carried out in a commercial nursery in Maryland (US). In later experiments, CLVd could be detected in Columnea cultivars obtained from European nurseries (no further details provided) but not from Columnea specimens collected from Costa Rica. So far, the origin of CLVd remains unknown. CLVd was also detected in other symptomless ornamentals: Brunfelsia undulata (Solanaceae) and Nematanthus wettsteini (Gesneriaceae). CLVd can naturally infect tomato and causes severe symptoms resembling those of Potato spindle tuber viroid (Pospiviroid, PSTVd – EPPO A2 List): stunting, leaf distortion and chlorosis. In the United Kingdom, leaf reddening (‘bronzing’) and necrosis were also prominent symptoms. Potato (Solanum tuberosum) is a potential host of CLVd. During experiments, the viroid could be mechanically transmitted to potato plants and symptoms resembling those of PSTVd could be observed. Long distance spread of CLVd is most likely to occur via infected plants or possibly by infected seed, although seed transmission has not yet been proven. CLVd can be transmitted from plant to plant by mechanical contact (direct plant-to-plant contact, infected tools and machinery, workers etc.).
Sources
NPPO of United Kingdom, 2007-08.
Hammon RW (2003) Columnea latent viroid. In: Viroids (eds Hadidi A, Flores R, Randles JW, Semancik JS) CSIRO Publishing, Collingwood (AU), pp 231-232.
INTERNET (last retrieved in 2008-01)
DEFRA website. Plant Health. Update: First UK findings of Columnea latent viroid on tomato production nurseries. http://www.defra.gov.uk/planth/newsitems/clvd.htm
APS website. APSnet Feature Story by Hammon RW, Owens RA (2006) Viroids: new and continuing risks for horticultural and agricultural crops. http://www.apsnet.org/online/feature/viroids/