Incidence in Cyprus of citrus exocortis viroid and its mechanical transmission

A survey for citrus exocortis viroid (CEV) was conducted in commercial groves of the main citrus-producing areas of Cyprus during 1987–1990. Of 573 trees sampled, representing 25 species and varieties, 506 (88.3%) were found to be infected when indexed by grafting to seedlings of'Etrog' citron (Citrus medica) , selection Arizona 861. Levels of infection by CEV were lower in newer introductions than in introductions made before the 1940s. In greenhouse tests, CEV was readily transmitted from citron to healthy citron and gynura (Gynura aurantiaca) by knife-blade inoculation. Retransmission of CEV from infected gynura back to citron was successful.