Development of a marker for detection of Xanthomonas campestris pv. campestris races 1 and 2 in Brassica oleracea

Abstract

Xanthomonas campestris pv. campestris (Xcc) is a plant pathogen of cruciferous crops that causes black rot disease throughout the world. At present, based on the host–pathogen interactions among differential cultivars of Brassica crops, 11 pathogenic Xcc races have been identified, but the race identification method based on host–pathogen interactions is time-consuming. However, early and rapid detection of the pathogen could reduce economic loss by allowing appropriate control measures against black rot disease to be taken more quickly. In this study, a PCR-based molecular marker has been developed for identifying the Xcc race 1 and Xcc race 2 bacterial strains together. The specificity of the marker was tested by PCR using 8 available Xcc races, X. campestris strains, and other bacteria. Upon amplification, a polymorphic band was observed in the PCR amplicon with a size of 1523 bp and 929 bp in Xcc races 1 and 2, respectively. A deletion of 594 bp conferred the specificity in Xcc race 2 compared to race 1. The identified PCR-based molecular marker clearly discriminated the Xcc race 1 and race 2 from other races when tested in artificially infected cabbage leaves. Thus, PCR-based development of an Xcc race 1- and 2-specific marker could be a valuable tool for the accurate detection of Xcc race 1 and 2 together for implementing control measures more quickly.