LOW PERFORMANCE OF CITRUS TREES GRAFTED ON CARRIZO CITRANGE IS ASSOCIATED WITH VIROID INFECTION
S.M. Bani Hashemian, N. Murcia, I. Trenor, N. Duran-Vila
After the implementation of a Citrus Variety Improvement Program in Spain, citrus cultivars free of virus and virus-like pathogens became available and cover today more than 70% of the citrus-growing regions of the country. In addition, because of the need to control tristeza, the main rootstock used in commercial plantings in Spain is Carrizo citrange. In spite of these developments, low performing orchards can still be found in certain areas in which tree vigor and fruit production are poor. Infection with viroids may have deleterious effects on the productivity of citrus species grafted on the viroid sensitive Carrizo citrange. Viroid infected trees were indeed found in low performing orchards of ‘Clemenules’ and ‘Afourer/Nadorcor’ clementines and ‘Ortanique’ tangor trees all grafted on Carrizo citrange. Bark scaling symptoms in the Carrizo citrange rootstock were always associated with CEVd infection but CBLVd, HSVd and CDVd were also consistently detected. The presence of viroid-infected and viroidfree trees in these orchards is discussed.