Differentiation of citrus bacterial canker strains in Korea by host range, rep-PCR fingerprinting and 16S rDNA analysis

New Xanthomonas isolates causing citrus bacterial canker in Korea were differentiated primarily on the basis of host range by comparison with reference strains. The new isolates were pathogenic to Citrus sinensis, C. paradisi, C. limon and C. unshiu and formed crater-like canker on the plants; this indicated that they were X. axonopodis (X.a.) pv. citri A types. Molecular characterization using rep-PCR fingerprinting and 16S rDNA sequence analysis was also performed. Cluster analysis by combining the band patterns of ERIC-, BOX- and REP-PCR clearly separated one group including only X. a. pv. citrumelo and the other group including X. a. pv. citri and X. a. pv. aurantifolii strains. There was a clear separation between X. a. pv. citri Asiatic types and X. a. pv. aurantifolii B, C types in the second group. Partial sequence analysis of 16S rDNA revealed that all strains of X. a. pv. aurantifolii B and C type, and X. a. pv. citrumelo formed a distinct cluster with a similarity of 99%. Our results indicate that the isolates causing citrus canker in Korea belong to the A type of X. a. pv. citri.