Viroids detected on tomato samples in the Netherlands
So far, the 5 following viroid species had been isolated from naturally infected tomatoes:
- Citrus exocortis pospiviroid (CEVd)
- Potato spindle tuber pospiviroid (PSTVd - EPPO A2 list)
- Tomato apical stunt pospiviroid (TASVd)
- Tomato chlorotic dwarf pospiviroid (TCDVd)
- Tomato planta macho pospiviroid (TPMVd)
Since 1988, the Dutch NPPO has occasionally detected viroids in tomato samples from the Netherlands or from other countries. Infected tomato plants showed chlorosis, bronzing, leaf distortion and growth reduction. It is stressed that all viroid infections found on tomato grown in the Netherlands were subsequently eradicated. Initial diagnosis of tomato viroids was done by r-PAGE which did not allow further identification. Further work was then done to identify 13 viroid isolates collected from tomatoes (from 1988 to 2002) by RT-PCR and sequence analysis. 4 viroid isolates were identified as CEVd, PSTVd and TCDVd. 6 isolates were identified as Columnea latent pospiviroid (CLVd), a viroid which was previously isolated from ornamental species only (Columnea undulata, Brunfelsia erythrophae, Nematanthus wettsteinii). During these studies, all viroid isolates were inoculated to tomato plants and potato plants under glasshouse conditions. All tomato plants showed growth reduction, leaf distortion and chlorosis. Potato plants did not show leaf symptoms but tubers were smaller and malformed. Potato plants grown from these infected tubers were severely stunted and also produced malformed tubers. During a trial period of 4 consecutive years, infected tubers were found to produce infected progeny. It is concluded that, considering the biological characteristics of all 4 viroids (CLVd, CEVd, PSTVd, TCDVd) especially their potential effects on both potato and tomato, their phytosanitary risks should be reconsidered.
Sources
Verhoeven JTJ, Jansen CCC, Willemen TM, Kox LFF, Owens RA, Roenhorst JW (2004) Natural infections of tomato by Citrus exocortis viroid, Columnea latent viroid, Potato spindle tuber viroid and Tomato chlorotic dwarf viroid.
European Journal of Plant Pathology, 110(8), 823-831.