Phenotypic and Genetic Diversity of Erwinia carotovora ssp. carotovora Strains from Asia

Abstract

A collection of 87 strains of the soft rot pathogen Erwinia carotovora ssp. carotovora (Ecc) isolated from various host plants in Japan, Korea and Thailand was characterized by bacteriological, pathological and genetic properties. On the basis of pathogenicity on the potato, tomato, onion and cucumber, strains were divided into four groups. They were also characterized by PCR‐restriction fragment length polymorphisms (RFLP) of 16S ribosomal DNA (rDNA), 16S‐23S rDNA intergenic spacer regions (ISRs) and a pel gene encoding pectate lyase. By analysis of 16S rDNA RFLP generated by Hinf I, Ecc strains were differentiated into two groups where it was discovered that most strains from Korea and Japan belonged to the same group. In the analysis of ISRs RFLP with MboI, two patterns were found. All Thai strains showed the same pattern. In the analysis of the pel gene RFLP with Sau3AI, all strains were separated into two independent patterns except for one strain. The strain (MAFF 301937) isolated from the mulberry showed a unique RFLP pattern of the pel gene. In cluster analysis based on 26 phenotypic characters, Ecc strains were composed of two groups, A and B. Group A contained typical Ecc strains which provided negative reactions in testing the production of reducing substances from sucrose and acids from α‐methyl glucoside. All Thai strains and most of the Korean strains belonged to group A, whereas group B contained atypical Ecc strains, which were isolated in Japan and Korea; the properties of this group were similar to those of E. carotovora ssp. atroseptica. The research reported here was undertaken to provide information on the strains of E. carotovora ssp. carotovora in Asia.