Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/14/2004
Publication Date: 9/2/2004
Citation: Halbert, S.E., Genc, H., Cevik, B., Brown, L.G., Rosales, I.M., Manjunath, K.L., Pomerinke, M., Davison, D.A., Lee, R.F., Niblett, C.L. 2004. Distribution and characterization of citrus tristeza virus in south florida following establishment of toxoptera citricida. Plant Disease 88:935-941. Interpretive Summary: The spread of Citrus tristeza virus was documented in three locations in the southeast urban corridor of Florida (Kendall, Fort Lauderdale and Delray Beach) in the two years following the establishment of Toxoptera citricida, the most efficient vector of CTV, in Florida. Molecular methods which differentiate mild, decline, and stem pitting CTV strains were used for analyses of the CTV isolates. The field isolates of CTV commonly contained a mixture of strains having different biological activity. Mexican lime trap plants were placed in a field in southwest Florida, and some of the plants became infected with isolates of CTV causing stem pitting. This is the first documentation of the occurrence and spread of CTV strains causing stem pitting in Florida. The data indicates that there has been an increase in CTV strain diversity as well as an increase in the occurrence and spread of severe CTV strains following the establishment of T. citricida. The data suggests that strains prevalent in one area may not be common in another area. The Florida Citrus Budwood Protection Program currently uses the monoclonal antibody MCA 13 to differentiate between mild and severe (decline and stem pitting) strains of CTV; budwood containing isolates of CTV which do not react with MCA 13 may be used for propagation. The results suggest that CTV isolates which do not react with MCA 13 could contain CTV strains which may cause decline or stem pitting.
Technical Abstract: The incidence of Citrus tristeza virus (CTV) was found to increase significantly in southern Florida within two years after the establishment of its most efficient vector, Toxoptera citricida (Kirkaldy). The increased incidence of both mild and severe strains was documented, with the incidence of severe strains increasing more than mild strains. Molecular probes capable of differentiating mild, quick decline and various types of stem pitting strains demonstrated that trees often were infected with more than one strain of CTV, with trees containing up to five different strains. Trees that initially tested negative for CTV later were found to be infected with several different strains. Some CTV strains detected in the southeast urban corridor of Florida (Kendall, Fort Lauderdale and Delray Beach) reacted with probes specific for stem-pitting strains known from elsewhere in the world. Several Mexican lime trap plants placed in commercial groves in southwest Florida also became infected with a strain reacting to the probe specific for stem-pitting strains. The presence of strains reacting with the specific probes was verified by amplifying, cloning and sequencing the capsid protein genes of the CTV strains present in representative trees and confirming the presence of the sequences reactive with those specific probes. The implications of the presence of these CTV strains in Florida and the possible presence in citrus budwood scion trees are discussed.