PCR-based detection of Xanthomonas campestris pv. phaseoli var. fuscans in plant material and its differentiation from X. c. pv. phaseoli

Abstract

A PCR-based method was developed for the specific detection of Xanthomonas campestris pv. phaseoli var. fuscans from plant material. Primers Xf1 and Xf2, based on a sequence conserved amplified region (SCAR) derived from RAPD PCR analysis of X. c. pv. phaseoli var. fuscans, amplified a DNA fragment of 450 bp from all such isolates. In contrast, no amplification product was obtained from any X. c. pv. phaseoli isolates, or from any other DNAs tested. As few as 10 cells of X. c. pv. phaseoli var. fuscans (equivalent to about 100 fg DNA) could be detected in vitro. In planta, following an initial inoculation of as little as one cell, an amplification product was generated after only 2 d of incubation, allowing highly sensitive detection 10 d before disease symptoms were observed. Moreover, the failure to amplify DNA from X. c. pv. phaseoli isolates shows that these primers provide a rapid, improved method to differentiate these two varieties using PCR.