Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/25/2004
Publication Date: 11/1/2004
Citation: Sun, Xiaoan, Stall, R. E., Cubero, J., Gottwald, T. R., Graham, J. H., Dixon, W. N., Schubert, T. S., Chaloux, P. H., Jones, J. B., Stromberg, V. K., Lacy, G. H., Sutton, B. D. 2004. Detection and Characterization of a New Strain of Citrus Canker Bacteria from Key/Mexican Lime (Citrus Aurantifolia) and Alemow (C. Macrophylla) in South Florida. Phytopathology. Interpretive Summary:
Technical Abstract: In the Wellington and Lake Worth areas of Palm Beach Co., Florida, Asiatic citrus canker has appeared on key/Mexican lime (Citrus aurantiifolia) and alemow (C. macrophylla)over a period of about 6-7 years, but nearby canker-susceptible citrus, such as grapefruit (C. x paradisi) and sweet orange (C. sinensis), were unaffected. The causal bacterium was easily isolated from leaf, stem, and fruit lesions. Colonies on nutrient agar appeared similar to those from the Asiatic group of strains of Xanthomonas axonopodis pv. citri (Xac-A), but the growth on lima bean agar slants was less mucoid. When inoculated, the bacterium produced a typical Asiatic citrus canker syndrome on key/Mexican lime, but brownish, flat, and necrotic lesions on the leaves of Duncan grapefruit, Madame Vinous sweet orange, sour orange (C. aurantium), citron (C. medica), Orlando tangelo (C. reticulata x C. x paradisi), and trifoliate orange (Poncirus trifoliata). The bacterium did not react with the Xac-A specific monoclonal antibody A1 using ELISA and could not be detected by commonly used PCR-based Xac-A assays. DNA reassociation analysis confirmed that the pathogen, designated as Xac-Aw, is more closely related to the strains of Xac-A and Xac-A* that was recently found in Southwest Asia than the B strain of citrus canker and citrus bacterial spot pathogen (Xanthomonas axonopodis pv. citrumelo). However, results obtained from fatty acid analysis, restriction endonuclease profiles of genomic DNA generated by Spel and Xbal, and host specificity demonstrated that the strain is different from Xac-A and Xac-A*, indicating that the strain should be designated as a pathovar and current designated pathovars should be elevated to an upper classification unit accordingly.