It was first confirmed in UK crops in 2007, with a further outbreak in 2009, and it spread rapidly. CLVd is notifiable and statutory action is taken on all outbreaks.
Symptoms are pale/chlorotic plants, leaf bronzing, reddening and necrosis, leaf deformation and bunching at the top of the plant. Once an infection source is established, CLVd is easily spread.
There is conflicting evidence for seed transmission. In the 2007 outbreaks, seed-borne infection was strongly implicated because simultaneous outbreaks occurred at different sites with the only common factor being the same variety and source of seed.
HDC project PC 294 set out to detect infected seed and latent infection in seedlings, validate detection methods, determine the type and frequency of seed-borne infection and screen products for their efficacy as treatments.
More than 25,000 seeds from the source related to earlier outbreaks, known to carry inoculum at around the one per cent level, were grown for nine weeks but none of the plants tested positive. Further seeds were produced from artificially inoculated plants, treated and then grown out, but produced no CLVd-positive seedlings. If seed transmission occurs, it is at less than the 0.5 per cent level.
The Food & Environment Research Agency provides a validated test for detecting CLVd in tomato seed. Seed can be screened for potato spindle tuber viroid infection at the same time.
HDC Fact Sheet 09/06 Potato spindle tuber viroid in tomato and new viroid reports.
Horticultural Development Company
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