Abstract
CTV is the most economically important virus pathogen of citrus worldwide. About 100 million citrus trees on sour orange have been killed by CTV decline epidemics in Argentina, Brazil, Venezuela, Peru, Florida and California (USA), Israel, Spain, and other locations. With current estimates of approximately 45 million trees on sour orange killed by CTV in Spain (Cambra et al., 2000a; Vidal et al., 2012) from 1935 to date without T. citricida implication. It is estimated that worldwide, mainly in the Mediterranean basin citrus industries, there are over 200 million trees on sour orange rootstock which are at risk to this disease. Sour orange is popular because it produces a vigorous tree with high quality fruit, is adaptable to many soil conditions including high lime and salt content, and has tolerance to many other viruses, viroids and virus-like pathogens, and to Phytophthora. The use of tristeza-tolerant rootstocks often risks losses from other factors. In addition to decline, many severe CTV isolates cause stem pitting diseases of susceptible scion cultivars and these occur even when tolerant rootstocks are used. Stem pitting weakens trees and eventually reduces fruit size, quality and quantity (Marais et al., 1996). Grapefruit and lime are very sensitive to stem pitting. Sweet orange is more tolerant but can be severely affected by some isolates. Mandarin is the most tolerant among the main citrus cultivars against SP isolates.
Failure of 100 Mild Citrus Tristeza Virus Isolates from California to Cross Protect Against a Challenge by Severe Sweet Orange Stem Pitting Isolates
