Detection of the bean common blight bacteria, Xanthomonas campestris pv. phaseoli and X. c. phaseoli var. fuscans, using the polymerase chain reaction

A 3.4-kb plasmid DNA fragment (p7) of Xanthomonas campestris pv. phaseoli that hybridizes specifically to X. c. phaseoli was subcloned and partially sequenced to design primers for a polymerase chain reaction (PCR) assay for the detection of bacteria causing common blight in bean. In Southern hybridization experiments, p7X3 and p7X4 subfragments showed high specificity for total genomic DNA of pathogenic X. c. phaseoli, whereas the p7X2 segment also weakly hybridized to DNA extracted from some strains belonging to other X. campestris pathovars. For each of these p7 fragments, a set of G + C-rich oligonucleotide primers was devised and tested under high-stringency conditions in PCR assays