• Research in Plant Disease
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• v.16 no.1
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• pp.35-40
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• 2010

Suppression effect of the 12 bacterial isolates from plant rhizosphere against late blight caused by Phytophthora citrophthora were investigated on citrus fruits. Among the bacterial isolates, THJ609-3, TRH423-3, BRH433-2, Lyso-chit and KRY505-3 presented disease suppression after wound inoculation with the fungal pathogen in vivo. The anti-fungal activity was evaluated by measuring the length of inhibition zone of the mycelium P. citrophthora adjacent to the effective bacterial isolates in which all of the 5 bacterial isolates showed antagonistic effects. However, there was no positive correlations between the efficacy of disease suppression and the antagonistic effect. On the other hand, Lyso-chit and KRY505-3 were identified as Bacillus cereus, BRH433-2 as B. circulans and TRH423-3 as Burkholderia gladioli, respectively, by analysis of rDNA sequence on the internal transcript spaces. It is suggested that the effective bacterial isolates may be useful for finding biological control agents against late blight especially on environment-friendly farm where the application of fungicide is limited.

• Microbiology and Biotechnology Letters
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• v.46 no.4
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• pp.346-359
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• 2018

Xanthomonas oryzae, a bacterial pathogen causing leaf blight disease (BLB) in rice, can cause widespread disease and has caused epidemics globally, resulting in severe crop losses of 50% in Asia. The pathogen is seed-borne and is transmitted through seeds. Thus, control of BLB requires the elimination of the pathogen from seeds. Concern about environment-friendly organic production has spurred improvements in a variety of biological disease control methods, including the use of bacteriophages, against bacterial plant pathogens. The present study explored the potential of bacteriophages isolated from diseased plant leaves and soil samples in killing the bacterial pathogen in rice seeds. Eight different phages were isolated and evaluated for their bacteriolytic activity against different pathogenic X. oryzae strains. Of these, a phage designated ${\varphi}XOF4$ killed all the pathogenic X. oryzae strains and showed the broadest host range. Transmission electron microscopy of ${\varphi}XOF4$ revealed it to be a tailed phage with an icosahedral head. The virus was assigned to the family Siphoviridae, order Caudovirales. Seedlings raised from the seeds treated with $1{\times}10^8pfu/ml$ of ${\varphi}XOF4$ phage displayed reduced incidence of BLB disease and complete bacterial growth inhibition. The findings indicate the potential of the ${\varphi}XOF4$ phage as a potential biological control agent against BLB disease in rice.

• Research in Plant Disease
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• v.10 no.1
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• pp.73-77
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• 2004

The gene analysis of resistance in rice cultivars, Daeanbyeo, Hwasunchalbyeo, Daejinbyeo, Naepungbyeo, Hwajinbyeo and Surabyeo to strains of Xanthomonas oryzae pv. oryzae was studied. F$_1$ plants and F$_2$ populations from the crosses between six cultivars and near isogenic lines carrying the single bacterial blight(BB) resistance gene were analyzed using Korean and Japanese BB races. Daeanbyeo, Hwasunchalbyeo, Daejinbyeo, Naepungbyeo, Hwajinbyeo and Surabyeo are alleic with IRBB101 but are non-alleic with IRBB104 and IRBB105. The allelic tests indicated that Daeanbyeo, Hwasunchalbyeo, Daejinbyeo, Naepungbyeo, Hwajinbyeo and Surabyeo have the Xal gene for resistance.

• The Plant Pathology Journal
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• v.37 no.4
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• pp.396-403
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• 2021

Fire blight disease, caused by Erwinia amylovora, could damage rosaceous plants such as apples, pears, and raspberries. In this study, we designed to understand how E. amylovora affected other bacterial communities on apple rhizosphere; twig and fruit endosphere; and leaf, and fruit episphere. Limited studies on the understanding of the microbial community of apples and changes the community structure by occurrence of the fire blight disease were conducted. As result of these experiments, the infected trees had low species richness and operational taxonomic unit diversity when compared to healthy trees. Rhizospheric bacterial communities were stable regardless of infection. But the communities in endosphere and episphere were significanlty affected by E. amylovora infection. We also found that several metabolic pathways differ significantly between infected and healthy trees. In particular, we observed differences in sugar metabolites. The finding provides that sucrose metabolites are important for colonization of E. amylovora in host tissue. Our results provide fundamental information on the microbial community structures between E. amylovora infected and uninfected trees, which will contribute to developing novel control strategies for the fire blight disease.

• The Plant Pathology Journal
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• v.38 no.3
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• pp.248-253
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• 2022

Erwinia amylovora is a devastating bacterial plant pathogen that infects Rosaceae including apple and pear and causes fire blight. Bacteriophages have been considered as a biological control agent for preventing bacterial infections of plants. In this study, nine bacteriophages (ΦFifi011, ΦFifi044, ΦFifi051, ΦFifi067, ΦFifi106, ΦFifi287, ΦFifi318, ΦFifi450, and ΦFifi451) were isolated from soil and water samples in seven orchards with fire blight in Korea. The genetic diversity of bacteriophage isolates was confirmed through restriction fragment length polymorphism pattern analysis. Host range of the nine phages was tested against 45 E. amylovora strains and 14 E. pyrifoliae strains and nine other bacterial strains. Among the nine phages, ΦFifi044 and ΦFifi451 infected and lysed E. amylovora only. And the remaining seven phages infected both E. amylovora and E. pyrifoliae. The results suggest that the isolated phages were different from each other and effective to control E. amylovora, providing a basis to develop biological agents and utilizing phage cocktails.

• Biodesign
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• v.7 no.2
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• pp.35-37
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• 2019

Xanthomonas oryzae pv. oryzae (Xoo) is a plant pathogen, which causes a bacterial blight of rice. The bacterial blight is one of the most devastating diseases of rice in most of the rice growing countries and there is no effective pesticide against bacterial blight. The β-ketoacyl-acyl carrier protein synthase III (FabH) plays a key role in fatty acid synthesis (FAS) and is a promising drug target for the development of antibacterial agents. Xoo0878 gene, a fabH gene, from Xoo was cloned and its gene product Xoo0878 was expressed, purified and crystallized. Xoo0878 crystal diffracted to 2.1Å resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 57.3Å, b = 64.7Å, c = 104.2Å and α = 81.6°, β = 84.7°, γ = 74.4°. There are four monomers in the asymmetric unit, with a corresponding crystal volume per protein weight of 2.65 ų Da^-1 and a solvent content of 53.6%. Xoo0878 structure will be useful to develop new antibacterial agents against Xoo.

• The Plant Pathology Journal
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• v.40 no.2
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• pp.225-232
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• 2024

The microbiomes of two important rice cultivars in Vietnam which differ by their susceptibility to the bacterial leaf blight (BLB) disease were analyzed through 16S rRNA amplicon technology. A higher number of operational taxonomic units and alpha-diversity indices were shown in the BLB-resistant LA cultivar than in the BLB-susceptible TB cultivar. The BLB pathogen Xanthomonas was scantly found (0.003%) in the LA cultivar, whereas was in a significantly higher ratio in the TB cultivar (1.82%), reflecting the susceptibility to BLB of these cultivars. Of special interest was the genus Acholeplasma presented in the BLB-resistant LA cultivar at a high relative abundance (22.32%), however, was minor in the BLB-sensitive TB cultivar (0.09%), raising a question about its roles in controlling the Xanthomonas low in the LA cultivar. It is proposed that Acholeplasma once entered the host plant would hamper other phytopathogens, i.e. Xanthomonas, by yet unknown mechanisms, of which the triggering of the host plants to produce secondary metabolites against pathogens could be a testable hypothesis.

• Research in Plant Disease
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• v.19 no.3
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• pp.177-182
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• 2013

Resvestrol has been known to inhibit bacterial and fungal growth in vitro, and can be accumulated in plant to concentrations necessary to inhibit microbial pathogens. Hence, stilbene synthase gene has been used to transform to synthesize resveratrol in heterologous plant species to enhance resistance against pathogens. In the present study, we investigated the antimicrobial activities of resveratrol and piceid to bacterial and fungal pathogens, which causing severe damages to rice plants. In addition, disease resistance was compared between transgenic rice varieties, Iksan 515 and Iksan 526 transformed with stlibene synthase gene and non-transgenic rice varieties, Dongjin and Nampyeong. Minimum inhibitory concentration of resveratrol for Burkolderia glumae was 437.5 ${\mu}M$, and the mycelial growth of Biplaris oryzae was slightly inhibited at concentration of 10 ${\mu}M$. However, other bacterial and fungal pathogens are not inhibited by resveratrol and piceid. The expression of the stilbene synthase gene in Iksan 515 and Iksan 526 did not significantly enhanced resistance against bacterial grain rot, bacterial leaf blight, sheath blight, and leaf blight. This study is the first report on the effect of resveratrol and piceid against pathogens of rice plant, and changes of disease resistance of transgenic rice plants transformed with stilbene synthase gene.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.419-423
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• 2003

Bacterial blight caused by Xantomonas oryzae pv. oryzae is one of the most serious diseases of rice especially in southern area of Korea. Three races, $\textrm{K}_1$, $\textrm{K}_2$ and $\textrm{K}_3$, are the most dominant species. lo improve rice breeding efficiency using marker assisted selection, some RFLP markers were surveyed for polymorphism between resistant and susceptible to $\textrm{K}_1$ and $\textrm{K}_3$. And, 127 doubled-haploid (DH) lines derived from Milyang121/HRl1650-1-4-2 and 131 DH lines derived from Milyang123/HR10624-AC5 were evaluated to bacterial blight ($\textrm{K}_1$ and $\textrm{K}_3$). Milyang121 and HR10624-AC5 have Xa-1, resistant to $\textrm{K}_1$ race, and Milyang123 has Xa-3, resistant to $\textrm{K}_1$ and $\textrm{K}_3$ race. Three markers, RZ590, RZ536 and RG303, showing polymorphism between parents and resistance gene, Xa-1 and Xa-3, were analysed in the two combinations of DH lines. The segregation pattern of resistant DH population of Milyang123/HR10624-AC5 to susceptible showed 3:1 and 1:1 in $\textrm{K}_1$ and $\textrm{K}_3$ race. In three RFLP markers, RZ590 was linked to Xa-1 on chromosome 4, and RZ536 and RG303 were linked to Xa-3 on chromosome 11. The map distance between Xa-1 and RZ590 was 3.1cM on chromosome 4, and Xa-3 and RZ536/RG303 were 7.6/16.0cM on chromosome 11, respectively. The results of RFLP mapping will be useful for the selection and pyramiding of bacterial blight resistant genes.

• The Plant Pathology Journal
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• v.34 no.2
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• pp.104-112
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• 2018

Accurate and rapid detection of bacterial plant pathogen is the first step toward disease management and prevention of pathogen spread. Bacterial plant pathogens Clavibacter michiganensis subsp. nebraskensis (Cmn), Pantoea stewartii subsp. stewartii (Pss), and Rathayibacter tritici (Rt) cause Goss's bacterial wilt and blight of maize, Stewart's wilt of maize and spike blight of wheat and barley, respectively. The bacterial diseases are not globally distributed and not present in Korea. This study adopted comparative genomics approach and aimed to develop specific primer pairs to detect these three bacterial pathogens. Genome comparison among target pathogens and their closely related bacterial species generated 15-20 candidate primer pairs per bacterial pathogen. The primer pairs were assessed by a conventional PCR for specificity against 33 species of Clavibacter, Pantoea, Rathayibacter, Pectobacterium, Curtobacterium. The investigation for specificity and sensitivity of the primer pairs allowed final selection of one or two primer pairs per bacterial pathogens. In our assay condition, a detection limit of Pss and Cmn was $2pg/{\mu}l$ of genomic DNA per PCR reaction, while the detection limit for Rt primers was higher. The selected primers could also detect bacterial cells up to $8.8{\times}10^3cfu$ to $7.84{\times}10^4cfu$ per gram of grain seeds artificially infected with corresponding bacterial pathogens. The primer pairs and PCR assay developed in this study provide an accurate and rapid detection method for three bacterial pathogens of grains, which can be used to investigate bacteria contamination in grain seeds and to ultimately prevent pathogen dissemination over countries.