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Erwinia pyrifoliae, a Causal Endemic Pathogen of Shoot Blight of Asian Pear Tree in Korea
Shrestha, Rosemary,Koo, Jun-Hak,Park, Duck-Hwan,Hwang, In-Gyu,Hur, Jang-Hyun,Lim, Chun-Keun The Korean Society of Plant Pathology 2003 Plant Pathology Journal Vol.19 No.6
Bacterial strains were isolated from diseased samples of shoot blight collected from different pear growing orchards of Chuncheon, Korea from 1995 to 1998. Forty-nine strains showed their pathogenicity on immature fruit and shoot of pear. Microbiological, physiological, and biochemical tests were performed on these pathogenic strains. One strain, designated as WT3 in this study, was selected as a representative strain as it was collected from the first outbreak area in Jichonri, Chuncheon in 1995. Further detailed characterization of the strain WT3 was done by PCR amplification using specific primers described previously for distinguishing Erwinia pyrifoliae from its close pathogen Erwinia amylovora. Based on phenotypical, biochemical, and molecular analyses, strain WT3 was identified as a shoot blight pathogen which was the same as E. pyrifoliae Ep16 previously described by a German group in 1999.
Rosemary Shrestha,임춘근,이선화,허장현 한국식물병리학회 2005 Plant Pathology Journal Vol.21 No.2
In this comparative study, the effects of temperature,pH, and bactericides on the growth of Erwinia pyrifoliae and Erwinia amylovora were investigated. The maximum temperature for the growth of both Erwinia species was estimated to be 36oC. The maximum specific growth rates of E. pyrifoliae and E. amylovora were observed at 27oC and 28oC, respectively, and no significant growth differences were shown at their optimum temperatures.However, at lower temperatures ranging from 12-21oC, E. pyrifoliae showed higher growth rates with doubling times shorter than those of E. amylovora. Distinct growth rates at these temperatures revealed that E.pyrifoliae is more cold-tolerant than E. amylovora. The optimum pH for the growth of both pathogens was 7.5 and growth was not seen at pH ≤ 5.0 and ≥ 10.0. These results showed that the effect of pH on the growth of E. pyrifoliae and E. amylovora was similar. Minimum inhibitory concentrations (MICs) of copper sulfate,oxolinic acid, streptomycin, and tetracycline, which inhibited growth of E. pyrifoliae and E. amylovora, were determined. The strains of both pathogens were able to grow at 0.08-0.32 mM copper sulfate, but not at higher concentrations. However, none of the tested strains grew in the presence of oxolinic acid (0.001 mM), streptomycin (0.1 mM), and tetracycline (0.01 mM) concentrations. These results suggested that all strains of both Erwinia species were sensitive to tested bactericides and indicated no occurrence of resistant strains of E. pyrifoliae in Korea.
Shrestha, Rosemary,Lee, Seon-Hwa,Hur, Jang-Hyun,Lim, Chun-Keun The Korean Society of Plant Pathology 2005 Plant Pathology Journal Vol.21 No.2
In this comparative study, the effects of temperature, pH, and bactericides on the growth of Erwinia pyrifoliae and Erwinia amylovora were investigated. The maximum temperature for the growth of both Erwinia species was estimated to be $36{\circ}C$. The maximum specific growth rates of E. pyrifoliae and E. amylovora were observed at $27{\circ}C$ and $28{\circ}C$, respectively, and no significant growth differences were shown at their optimum temperatures. However, at lower temperatures ranging from 12-$21{\circ}C$, E. pyrifoliae showed higher growth rates with doubling times shorter than those of E. amylovora. Distinct growth rates at these temperatures revealed that E. pyrifoliae is more cold-tolerant than E. amylovora. The optimum pH for the growth of both pathogens was 7.5 and growth was not seen at pH ${\le}$ 5.0 and ${\ge}$ 10.0. These results showed that the effect of pH on the growth of E. pyrifoliae and E. amylovora was similar. Minimum inhibitory concentrations (MICs) of copper sulfate, oxolinic acid, streptomycin, and tetracycline, which inhibited growth of E. pyrifoliae and E. amylovora, were determined. The strains of both pathogens were able to grow at 0.08-0.32 mM copper sulfate, but not at higher concentrations. However, none of the tested strains grew in the presence of oxolinic acid (0.001 mM), streptomycin (0.1 mM), and tetracycline (0.01 mM) concentrations. These results suggested that all strains of both Erwinia species were sensitive to tested bactericides and indicated no occurrence of resistant strains of E. pyrifoliae in Korea.
Rosemary Shrestha,박덕환,Jun Mo Cho,조세열,Calum Wilson,황인규,허장현,임춘근 한국분자세포생물학회 2008 Molecules and cells Vol.25 No.1
The disease-specific (dsp) region and the hypersensitive response and pathogenicity (hrp) genes, including the hrpW, hrpNEp, and hrpC operons have previously been sequenced in Erwinia pyrifoliae WT3 [Shrestha et al. (2005a)]. In this study, the remaining hrp genes, including the hrpC, hrpA, hrpS, hrpXY, hrpL and hrpJ operons, were determined. The hrp genes cluster (ca. 38 kb) was comprised of eight transcriptional units and contained nine hrc (hrp conserved) genes. The genetic organization of the hrp/hrc genes and their orientation for the transcriptions were also similar to and collinear with those of E. amylovora, showing ≥ 80% homologies. However, ORFU1 and ORFU2 of unknown functions, present between the hrpA and hrpS operons of E. amylovora, were absent in E. pyrifoliae. To determine the HR active domains, several proteins were prepared from truncated fragments of the N-terminal and the C-terminal regions of HrpNEp protein of E. pyrifoliae. The proteins prepared from the N-terminal region elicited HR, but not from those of the C-terminal region indicating that HR active domains are located in only N-terminal region of the HrpNEp protein. Two synthetic oligopeptides produced HR on tobacco confirming presence of two HR active domains in the HrpNEp. The HR positive Nterminal fragment (HNΔC187) was further narrowed down by deleting C-terminal amino acids and internal amino acids to investigate whether amino acid insertion region have role in faster and stronger HR activity in HrpNEp than HrpNEa. The HrpNEp mutant proteins HNΔC187 (D1AIR), HNΔC187 (D2AIR) and HNΔC187 (DM41) retained similar HR activation to that of wildtype HrpNEp. However, the HrpNEp mutant protein HNΔC187 (D3AIR) lacking third amino acid insertion region (102 to 113 aa) reduced HR when compared to that of wild-type HrpNEp. Reduction in HR elicitation could not be observed when single amino acids at different positions were substituted at third amino acids insertion region. But, substitution of amino acids at L103R, L106K and L110R showed reduction in HR activity on tobacco suggesting their importance in activation of HR faster in the HrpNEp although it requires further detailed analysis.