Physiological and Biochemical Characteristics of Iranian Strains of Xanthomonas axonopodis pv. citri, the Causal Agent of Citrus bacterial Canker Disease

Twenty-four strains of Xanthomonas axonopodis pv. citri (Xac), the causal agent of bacterial canker of citrus, isolated from Mexican lime (Citrus aurantifolia) and lemon (Citrus limon) in southern Iran, were charac- terized phenotypically. Strains were all pathogenic on C. aurantifolia. Sodium dodecyl sulphate-polyacryla- mide gel electrophoresis analysis revealed slight di€er- ences in soluble protein pro®les among the strains. Based on host range speci®city and phenotypic charac- teristics, representative strains were di€erentiated into two groups of Asiatic (A) and atypical Asiatic (aA) forms. DNA ®ngerprinting analysis using EcoRI as the restriction endonuclease showed a negligible di€erence in restriction pattern between the two groups. On the basis of isozymic analysis, the two groups were distinct with respect to superoxide dismutase (SOD) and ester- ase (EST) banding patterns. Plasmid DNA pro®le ana- lysis showed that the bacterial strains were di€erent from each other in terms of plasmid number and mole- cular weight. Phage typing study revealed that most of group A strains were susceptible to Cp1 and/or Cp2 and some were resistant to both phage types including the strain in aA group. Bacteriocin production test indicated that there was a variation among Xac strains using di€erent indicators for each bacteriocin producer. It is concluded that the Iranian strains of Xac are het- erogeneous and constitute a subgroup(s) within the pathotype A