MOLECULAR STUDY OF ERWINIA PYRIFOLIAE STRAINS BY PLASMID PROFILE, PHYLOGENETIC ANALYSIS AND PCR

Erwinia pyrifoliae, an endemic pathogen to Korea, causes shoot blight in Asian pear (Pyrus pyrifolia). So far, a limited number of studies have been attempted to investigate diversity and genetic relationships of E. pyrifoliae strains. In this study, various strains of E. pyrifoliae, which were isolated from pear orchards of Chuncheon from 1995–1998, were investigated in order to observe their genetic relationships by plasmid profile analysis, enterobacterial repetitive intergenic consensus (ERIC) and Box-PCR analyses and sequence analysis of conserved 16S-23S intergenic transcribed spacer (ITS) region and groEL gene. PCR-based method was also developed for identification of E. pyrifoliae using specific primer pair (EpSPF-EpSPR). To date, only one type of plasmid profile has been reported from E. pyrifoliae. However, in this study, four types of plasmid profiles were observed for the first time suggesting occurrence of intra-specific plasmid profile diversity in E. pyrifoliae. Moreover, Box-PCR and phylogenetic analysis based on 16S-23S intergenic transcribed spacer (ITS) region showed genetic variations among E. pyrifoliae strains although all strains were clustered in one group and separated from fire blight pathogen E. amylovora. On the other hand, ERIC-PCR and phylogenetic analysis based on partial groEL gene sequences revealed close genetic relatedness among the strains. The EpSPF and EpSPR primers amplified approximately 0.65 kb fragment from the genomic DNA of all E. pyrifoliae strains but not from E. amylovora strains. This result apparently showed genetic difference between two close pathogens; furthermore, this result suggested that the primer set can be used for identification of E. pyrifoliae.