PCR-based assay for the detection of Xanthomonas euvesicatoria causing pepper and tomato bacterial spot.

AIMS To develop a PCR-based assay for Xanthomonas euvesicatoria detection in culture and in planta. METHODS AND RESULTS A fragment of 1600 bp specific for X. euvesicatoria was found by repetitive extragenic palindromic sequence-PCR. Among the primers designed on the basis of the partially sequenced fragment, the primers Xeu2.4 and Xeu2.5 direct amplification of the expected product (208 bp) for all the X. euvesicatoria strains and not for other related and unrelated phytopathogenic bacteria or saprophytic bacteria isolated from pepper and tomato phyllosphere. The assay permits the detection of X. euvesicatoria in pure culture, with a limit of detection of two bacterial cells and 1 pg of DNA per PCR, and in extracts obtained from asymptomatic inoculated tomato and pepper plants. CONCLUSIONS Primers Xeu2.4 and Xeu2.5 provide a specific, sensitive and rapid assay for the detection of X. euvesicatoria in culture and in pepper and tomato plants. SIGNIFICANCE AND IMPACT OF THE STUDY Because X. euvesicatoria is a quarantine organism in the European Union, and it is subjected to stringent international phytosanitary measures, this highly sensitivity PCR-based assay is suitable for its detection in pepper and tomato plant materials to avoid the introduction and spread of the bacterium.