RAPD PCR-BASED DIFFERENTIATION OF XANTHOMONAS-CAMPESTRIS PV. PHASEOLIAND XANTHOMONAS-CAMPESTRIS PV. PHASEOLI VAR. FUSCANS

A RAPD PCR-based method was used to differentiate between isolates of Xanthomonas campestris pv. phaseoli and Xanthomonas campestris pv. pha seoli var. fuscans. Using random primer OP-G11, a single, high intensi ty band of 820 bp was amplified from DNAs of all X. c. pv. phaseoli va r. fuscans isolates, while multiple amplification products of varying sizes were generated from X. c. pv. phaseoli DNAs. Whereas RAPD PCR di fferentiation gave an unambiguous result in under 4 h, standard differ entiation by recording the production of a brown pigment by X. c. pv. phaseoli var. fuscans isolates took up to 7 days and showed variation both between isolates and between media. The unequivocal nature of the RAPD PCR method was demonstrated when isolate 408, originally classif ied as X. c. pv, phaseoli var. fuscans, failed to produce the 820 bp b and typical of X. c. pv. phaseoli var. fuscans isolates, and after als o failing to produce a brown pigment, was re-classified as X. c. pv. p haseoli.