Chronic infection of the citrus tristeza virus in Citrus sinensis / C. aurantium trees in a restrictive thermal regime in Yucatán

Abstract The citrus tristeza virus (CTV) is a pathogen present in almost all citrus areas. It reduces production in plantations with susceptible rootstocks, such as sour orange trees. The aim of this study was to temporally characterize the behavior of CTV considering its population structure (PS), vigor, concentration in tissues and availability of vectors, this on the basis of an analysis of the thermal conditions in Yucatán. In two sweet orange (C. sinensis) orchards in Yucatán, trees grafted onto sour orange (C. aurantium) were sampled and evaluated in terms of vigor for 12 years. Samples were analyzed by immunoprinting, single-strand conformation polymorphism (SSCP), and specific amplifications by real-time and conventional polymerase chain reaction (PCR). The incidence of CTV increased 40 % in four years. All samples analyzed (81) were negative for severe isolates; only T-30 isolates and minor changes in tree vigor were identified. The PS indicated changes with a tendency towards complexity (11 electrophoretic patterns in six haplotypes), a similarity coefficient of 0.80 and intrapopulation diversity of 65 %. The thermal regime (TR) was restrictive during 75 % of the year for CTV transmission and the optimum development of vector aphids. Pathogen PS and TR have contributed to the fact severe CTV epidemics have not been recorded; therefore, sour orange continues as a key element in the region’s citrus production despite the risk involved (commercializing propagating material that does not comply with NOM 079-FITO-2002).