Viroids
The PAGE-return electrophoresis method for potato spindle tuber viroid (an EPPO A2 quarantine pest) (cf. EPPO Bulletin Vol. 17(1), pp. 45-50) has been successfully tried out in Spain for this viroid and also for citrus exocortis viroid.
In a survey in Spain, viroids were found to be widespread in grapevine, but cannot immediately be associated with any particular disease. Meristem-tip culture is being tried out as a method for obtaining viroid-free plants, as a basis for further work on the importance, transmission and infectivity of these viroids. One (known as GV-s) has been sequenced and found to be closely related to citrus exocortis viroid. It may be noted that all grapevine and citrus virus or 'virus-like' diseases are considered of quarantine significance by EC countries (Annexes IA, IB).
In Italy, a viroid isolated from stunted carnation plants and provisionally named carnation stunting viroid is being characterized. The disease is also known in France, Israel and Portugal. The EPPO Panel on Certification of Pathogen-Tested Ornamentals examined this case and considered that association of the viroid with the disease is not yet fully demonstrated. In any case, the disease is conspicuous and easily eliminated by roguing. It has been known to occur very occasionally for many years and presents no significant threat to carnation certification systems.
Sources
Salgado C. et al. Potato spindle tuber viroid: completion of a new PAGE return detection method. Proceeding of the 7th Congress of the Mediterranean Phytopathological Union, Granada (ES), September 1987 p. 115.
Duran-Vila N. et al. Widespread occurrence of grapevine viroids and their elimination by shoot tip-culture. Proceeding of the 7th Congress of the Mediterranean Phytopathological Union, Granada (ES), September 1987 p. 77.
Garcia-Arenal F., Pallas V. & Flores R. Primary· structure and conformation model of a grapevine viroid closely related to severe isolates of citrus exocortis viroid. Proceeding of the 7th Congress of the Mediterranean Phytopathological Union, Granada (ES), September 1987 p. 170.
Boccardo G. et al. Studies on a viroid from stunted carnation. Proceeding of the 7th Congress of the Mediterranean Phytopathological Union, Granada (ES), September 1987 pp. 164-165.