Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 6/1/2005
Citation: Bock, C.H., Parker, P.E., Gottwald, T.R., Mavrodieva, V.A., Levy, L. 2005. Detecting and quantifying Xanthomonas axonopodis pv. citri in wind driven splash. Phytopathology. 95:6S11. Interpretive Summary:
Technical Abstract: The bacterium <i>Xanthomonas axonopodis</i> pv <i>citri</i> causes citrus canker and is presently under eradication in Florida. Identifying and quantifying bacteria is useful when investigating the epidemiology of the pathogen and can have application in monitoring dispersal of live bacteria. In a series of experiments using field collected samples of wind-blow splash, dilution plating was compared with an established citrus canker SYBR Green real-time PCR method for detection from symptomatic tissues using universal primers VM3+4. Of 314 samples tested, 235 (75%) agreed on detection. False negatives using PCR were found in 75 (24%) of samples, all of which contained 3 to 863 bacteria/per ml detected by dilution plating. Only 4 samples (1%) were positive using PCR, but not by dilution plating. There was a positive linear relationship between the real-time PCR score and log number of living bacteria collected/ml (0 to1.0x10<sup>5</sup>, R<sup>2</sup>=0.72), although a large range of living bacteria/ml existed within each PCR category. No modification was made to the PCR protocol and no splash-sample concentrating procedures were performed. The results confirmed previous observations on the sensitivity of real-time PCR for detecting citrus canker bacteria (10<sup>3</sup>/ml). Research to improve detection via real-time PCR at low concentrations is ongoing.