• 농업과학연구
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• 제50권4호
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• pp.723-734
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• 2023

Erwinia pyrifoliae, which causes black shoot blight in apple and pear trees, was first identified in Korea in 1995. Extensive measures are typically used to control the disease by eradicating trees in diagnosed orchards, owing to the detrimental impact of the disease on apple and pear production. However, despite governmental efforts, the disease has continuously spread. In this study, we analyzed the current status of the black shoot blight occurrence in apple and pear orchards between 1995 to 2022. Our findings reveal that over the past 28 years, black shoot blight has occurred in 26 cities and districts across five Korean provinces. The affected regions are predominantly concentrated in the northern part of Korea, including the Gangwon and Gyeonggi provinces. Furthermore, black shoot blight has gradually expanded to the northern provincial regions of Chungbuk, Chungnam, and Gyeongbuk, which are centrally situated in Korea. Furthermore, the occurrence pattern of black shoot blight differed between apple and pear orchards; in apple orchards, black shoot blight occurred consistently each year, with a sudden increase in cases in 2020; however, in pear orchards, it has considerably decreased since 2007. To the best of our knowledge, this is the first comprehensive report on the occurrence of black shoot blight in apple and pear trees in 28 years, and the results will provide valuable insights for future disease management strategies.

• The Plant Pathology Journal
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• 제34권3호
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• pp.191-198
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• 2018

Fast and accurate diagnosis is needed to eradicate and manage economically important and invasive diseases like fire blight. Loop-mediated isothermal amplification (LAMP) is known as the best on-site diagnostic, because it is fast, highly specific to a target, and less sensitive to inhibitors in samples. In this study, LAMP assay that gives more consistent results for on-site diagnosis of fire blight than the previous developed LAMP assays was developed. Primers for new LAMP assay (named as DS-LAMP) were designed from a histidine-tRNA ligase gene (EAMY_RS32025) of E. amylovora CFBP1430 genome. The DS-LAMP amplified DNA (positive detection) only from genomic DNA of E. amylovora strains, not from either E. pyrifoliae (causing black shoot blight) or from Pseudomonas syringae pv. syringae (causing shoot blight on apple trees). The detection limit of DS-LAMP was 10 cells per LAMP reaction, equivalent to $10^4$ cells per ml of the sample extract. DS-LAMP successfully diagnosed the pathogens on four fire-blight infected apple and pear orchards. In addition, it could distinguish black shoot blight from fire blight. The $B{\ddot{u}}hlmann$-LAMP, developed previously for on-site diagnosis of fire blight, did not give consistent results for specificity to E. amylovora and on-site diagnosis; it gave positive reactions to three strains of E. pyrifoliae and two strains of P. syringae pv. syringae. It also, gave positive reactions to some healthy sample extracts. DS-LAMP, developed in this study, would give more accurate on-site diagnosis of fire blight, especially in the Republic of Korea, where fire blight and black shoot blight coexist.

• The Plant Pathology Journal
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• 제39권1호
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• pp.141-148
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• 2023

Black shoot blight disease caused by Erwinia pyrifoliae has serious impacts on quality and yield in pear production in Korea; therefore, rapid and accurate methods for its detection are needed. However, traditional detection methods require a great deal of time and fail to achieve absolute quantification. In the present study, we developed a droplet digital polymerase chain reaction (ddPCR) method for the detection and absolute quantification of E. pyrifoliae using a pair of species-specific primers. The detection range was 10³-10⁷ copies/ml (DNA templates) and cfu/ml (cell culture templates). This new method exhibited good linearity and repeatability and was validated by absolute quantification of E. pyrifoliae DNA copies from samples of artificially inoculated immature pear fruits. Here, we present the first study of ddPCR assay for the detection and quantification of E. pyrifoliae. This method has potential applications in epidemiology and for the early prediction of black shoot blight outbreaks.

• The Plant Pathology Journal
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• 제36권5호
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• pp.428-439
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• 2020

Erwinia pyrifoliae is a Gram-negative bacterial plant pathogen that causes black shoot blight in apple and pear. Although earlier studies reported the genome comparison of Erwinia species, E. pyrifoliae strains for such analysis were isolated in 1996. In 2014, the strain E. pyrifoliae EpK1/15 was newly isolated in the apple tree showing black shoot blight in South Korea. This study aimed to better understand the similarities and differences caused by natural variations at the genomic level between newly isolated E. pyrifoliae EpK1/15 and the strain Ep1/96, which were isolated almost 20 years apart. Several comparative genomic analyses were conducted, and Clusters of Orthologous Groups of proteins (COG) database was used to classify functional annotation for each strain. E. pyrifoliae EpK1/15 had similarities with the Ep1/96 strain in stress-related genes, Tn3 transposase of insertion sequences, type III secretion systems, and small RNAs. The most remarkable difference to emerge from this comparison was that although the draft genome of E. pyrifoliae EpK1/15 was almost conserved, Epk1/15 strain had at least three sorts of structural variations in functional annotation according to COG database; chromosome inversion, translocation, and duplication. These results indicate that E. pyrifoliae species has gone natural variations within almost 20 years at the genomic level, and we can trace their similarities and differences with comparative genomic analysis.

• 식물병과 농업
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• 제5권1호
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• pp.46-49
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• 1999

Bacterial blight occurred on the flowers, leaves, twigs and branches of apple trees (Malus domestica Borkh) in Chunchon, Kangwon-Do. Infected flowers and leaves turned brownish black, and they were fallen down or remained hanging in the trees. Under humid conditions during postblossom period, the casual bacterium spreaded along twigs and killed them. However, killing of branches was very rare. The symptoms on apple trees were very similar to symptoms of fire blight. But the causal organism isolated from the lesions was identified as Pseudomonas syringae based on physiological and chemical characteristics. This is the first described bacterium that causes apple shoot blight in Korea.

• The Plant Pathology Journal
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• 제38권3호
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• pp.194-202
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• 2022

Erwinia amylovora and Erwinia pyrifoliae cause fire blight and black-shoot blight, respectively, in apples and pears. E. pyrifoliae is less pathogenic and has a narrower host range than that of E. amylovora. Fire blight and black-shoot blight exhibit similar symptoms, making it difficult to distinguish one bacterial disease from the other. Molecular tools that differentiate fire blight from black-shoot blight could guide in the implementation of appropriate management strategies to control both diseases. In this study, a primer set was developed to detect and distinguish E. amylovora from E. pyrifoliae by conventional polymerase chain reaction (PCR). The primers produced amplicons of different sizes that were specific to each bacterial species. PCR products from E. amylovora and E. pyrifoliae cells at concentrations of 10⁴ cfu/ml and 10⁷ cfu/ml, respectively, were amplified, which demonstrated sufficient primer detection sensitivity. This primer set provides a simple molecular tool to distinguish between two types of bacterial diseases with similar symptoms.

• The Plant Pathology Journal
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• 제38권4호
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• pp.355-365
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• 2022

Erwinia amylovora and E. pyrifoliae are the causative agents of destructive diseases in both apple and pear trees viz. fire blight and black shoot blight, respectively. Since the introduction of fire blight in Korea in 2015, the occurrence of both pathogens has been independently reported. The co-incidence of these diseases is highly probable given the co-existence of their pathogenic bacteria in the same trees or orchards in a city/district. Hence, this study evaluated whether both diseases occurred in neighboring orchards and whether they occurred together in a single orchard. The competition and virulence of the two pathogens was compared using growth rates in vitro and in planta. Importantly, E amylovora showed significantly higher colony numbers than E. pyrifoliae when they were co-cultured in liquid media and co-inoculated into immature apple fruits and seedlings. In a comparison of the usage of major carbon sources, which are abundant in immature apple fruits and seedlings, E. amylovora also showed better growth rates than E. pyrifoliae. In virulence assays, including motility and a hypersensitive response (HR), E. amylovora demonstrated a larger diameter of travel from the inoculation site than E. pyrifoliae in both swarming and swimming motilities. E. amylovora elicited a HR in tobacco leaves when diluted from 1:1 to 1:16 but E. pyrifoliae does not elicit a HR when diluted at 1:16. Therefore, E. amylovora was concluded to have a greater competitive fitness than E. pyrifoliae.

• 식물병연구
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• 제23권4호
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• pp.306-313
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• 2017

최근 한국에서 화상병이 발생하였으며, 그 이후로 이병에 대한 박멸프로그램이 가동되고 있다. 본 연구에서는 2가지 항혈청기반 진단 스트립의 국내 분리 화상병균 Erwinia amylovora (Ea)에 대한 특이성과 검출민감도 그리고 현장진단에 적용을 평가하였다. 상업화된 Ea AgriStrip과 본 연구에서 개발한 EB strip은 검정에 사용한 모든 한국 Ea 균주들과 가지검은마름병을 일으키는 대부분의 Erwinia pyrifoliae (Ep)에 양성반응을 보여주었다. 사과나무 가지마름병을 일으키는 Pusedomonas syringae pv. syringae (Pss)의 사용한 모든 균주에 음성반응을 보여주었다. 2 스트립 사이에 검출민감도는 유사하였다. 현장진단의 경우, 2가지 스트립은 화상병이 발생한 모든 과수원에서 채취한 화상병징 세균추출액에 대하여 양성반응을 보였다. 그러나 겨울철에 진행된 한 곳의 화상병 현장진단에서는 화상병병징 세균추출액에 음성반응을 보였다. 또한 2가지 스트립은 가지검은마름병이 발생한 과수원에서 채집한 가지검은마름병징 세균추출액에 대해서 양성반응을 보여주었다. 이상의 결과는 Ea AgriStrip과 EB strip이 화상병 현장진단에 유용할 것으로 암시한다.

• The Plant Pathology Journal
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• 제34권5호
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• pp.445-450
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• 2018

Bacteriophages, bacteria-infecting viruses, have been recently reconsidered as a biological control tool for preventing bacterial pathogens. Erwinia amylovora and E. pyrifoliae cause fire blight and black shoot blight disease in apple and pear, respectively. In this study, the bacteriophage phiEaP-8 was isolated from apple orchard soil and could efficiently and specifically kill both E. amylovora and E. pyrifoliae. This bacteriophage belongs to the Podoviridae family. Whole genome analysis revealed that phiEaP-8 carries a 75,929 bp genomic DNA with 78 coding sequences and 5 tRNA genes. Genome comparison showed that phiEaP-8 has only 85% identity to known bacteriophages at the DNA level. PhiEaP-8 retained lytic activity up to $50^{\circ}C$, within a pH range from 5 to 10, and under 365 nm UV light. Based on these characteristics, the bacteriophage phiEaP-8 is novel and carries potential to control both E. amylovora and E. pyrifoliae in apple and pear.

• 식물병연구
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• 제22권4호
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• pp.269-275
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• 2016

E. pyrifoliae에 의한 과수 가지검은마름병은 국내에서 1995년 최초 발생이래 2016년까지 꾸준히 발생하여 과수농가에 피해를 주고 있는 세균병해이다. 가지검은마름병 발생 농가의 폐원조치 및 공적방제로 인한 경제적 피해 감소를 위하여, 병징이 관찰되는 이병조직 및 건전조직 내의 병원 세균을 검출하여 효율적 관리방안을 마련하고자 본 연구를 수행하였다. 가지검은마름병원세균의 검출은 genomic DNA 추출과정을 생략한 순수 균총만을 이용하는 colony-PCR을 이용하였으며, 이를 위해 ERIC 지역에서 제작된 가지검은마름병원세균 특이 프라이머 EpSPF/EpSPR 프라이머쌍을 선발하였다. 특이 프라이머를 활용한 colony-PCR 방법으로 2014-2015년 4-10월까지 사과나무 생육기간 동안 가지검은마름병 발생상황을 모니터링한 결과, $25^{\circ}C$ 일 평균 온도 기간인 5월 중순부터 7월 초순까지 발병이 가장 빈번하였다. 발병가지 내 병원세균의 존재유무 검정 결과 병징 부위와 이로부터 20 cm 내 건전조직에서만 병원세균이 지속적으로 검출되었다. 따라서 이미 발생한 가지검은마름병을 효율적으로 관리하기 위해 이병조직과 건전조직 경계 부위로부터 20 cm 이상에서 가지치기를 하는 것이 매우 적절할 것으로 판단된다.