• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.7-8
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• 2002

• The Plant Pathology Journal
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• v.20 no.1
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• pp.7-12
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• 2004

An important recent advance in the field of plant-microbe interactions has been the cloning of genes that confer resistance to specific viruses, bacteria, fungi or insects. Disease resistance (R) genes encode proteins with predicted structural motifs consistent with them having roles in signal recognition and transduction. Plant disease resistance is the result of an innate host defense mechanism, which relies on the ability of plant to recognize pathogen invasion and efficiently mount defense responses. In tomato, resistance to the pathogen Pseudomonas syringae pv. tomato is mediated by the specific recognition between the tomato serine/threonine kinase Pto and bacterial protein AvrPto or AvrPtoB. This recognition event initiates signaling events that lead to defense responses including an oxidative burst, the hypersensitive response (HR), and expression of pathogenesis- related genes.

• The Plant Pathology Journal
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• v.35 no.2
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• pp.137-148
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• 2019

In search of an effective biological control agent against the tomato pathogen Fusarium oxysporum f. sp. lycopersici, rhizospheric soil samples were collected from eight agro-ecological zones of Bangladesh. Among the bacteria isolated from soil, 24 isolates were randomly selected and evaluated for their antagonistic activity against F. oxysporum f. sp. lycopersici. The two promising antagonistic isolates were identified as Brevundimonas olei and Bacillus methylotrophicus based on morphological, biochemical and molecular characteristics. These two isolates were evaluated for their biocontrol activity and growth promotion of two tomato cultivars (cv. Pusa Rubi and Ratan) for two consecutive years. Treatment of Pusa Rubi and Ratan seeds with B. olei prior to inoculation of pathogen caused 44.99% and 41.91% disease inhibition respectively compared to the untreated but pathogen-inoculated control plants. However, treatment of Pusa Rubi and Ratan seeds with B. methylotrophicus caused 24.99% and 39.20% disease inhibition respectively. Furthermore, both the isolates enhanced the growth of tomato plants. The study revealed that these indigenous bacterial isolates can be used as an effective biocontrol agent against Fusarium wilt of tomato.

• Journal of Life Science
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• v.21 no.9
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• pp.1295-1300
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• 2011

The AtPGR gene is induced by pathogen infection, jasmonic acid and salicylic acid treatment and may therefore play a role in plant defense responses. Arabidopsis thaliana Plasma membrane Glucose-responsive Regulator (AtPGR) was previously isolated from Arabidopsis, which confers glucose insensitivity on plants. To study its biological functions directly, we have characterized both loss-of-function RNAi mutant and gain-of-function transgenic overexpression plants for AtPGR in Arabidopsis. The AtPGR-overexpressing plants displayed enhanced resistance to a virulent strain of the bacterial pathogen Pseudomonas syringae as measured by a significant decrease in both bacterial growth and symptom development as compared to those in wild-type and RNAi plants. The enhanced resistance in the gain-of-function transgenic plants was associated with increased induction of SA-regulated PDF1.2 and JA-regulated PR1 by the bacterial pathogen. Thus, pathogen-induced AtPGR plays a positive role in defense responses to P. syringae.

• The Plant Pathology Journal
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• v.35 no.5
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• pp.473-485
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• 2019

Kiwifruit (Actinidia spp.) is an economically important crop and a bacterial canker disease, caused by Pseudomonas syringae pv. actinidiae (Psa), is the most destructive disease in kiwifruit production. Therefore, prevent and control of the disease is a critical issue in kiwifruit industry worldwide. Unfortunately, there is no reliable control methods have been developed. Recently, interest in disease control using microbial agents is growing. However, kiwifruit microbiota and their roles in the disease control is mainly remaining unknown. In this study, we secured bacterial libraries from kiwifruit ecospheres (rhizosphere, endospere, and phyllosphere) and screened reliable biocontrol strains against Psa. As the results, Streptomyces racemochromogenes W1SF4, Streptomyces sp. W3SF9 and S. parvulus KPB2 were selected as anti-Psa agents from the libraries. The strains showed forcible antibacterial activity as well as exceptional colonization ability on rhizosphere or phyllosphere of kiwifruit. Genome analyses of the strains suggested that the strains may produce several anti-Psa secondary metabolites. Our results will contribute to develop biocontrol strains against the kiwifruit canker pathogen and the disease management strategies.

• The Plant Pathology Journal
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• v.24 no.3
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• pp.337-351
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• 2008

Host-pathogen interaction in rice bacterial blight pathosystem was analyzed for a better understanding of their relationship and recognition of stable pathogenicity among the populations of Xanthomonas oryzae pv. oryzae. A total number of 52 bacterial strains isolated from diseased leaf samples collected from 12 rice growing states and one Union Territory of India, were inoculated on 16 rice varieties, each possessing known genes for resistance. Analysis of variance revealed that the host genotypes(G) accounted for largest(78.4%) proportion of the total sum of squares(SS), followed by 16.5% due to the pathogen isolates(I) and 5.1% due to the $I{\times}G$ interactions. Application of the Additive Main effects and Multiplicative Interaction(AMMI) model revealed that the first two interaction principal component axes(IPCA) accounted for 66.8% and 21.5% of the interaction SS, respectively. The biplot generated using the isolate and genotypic scores of the first two IPCAs revealed groups of host genotypes and pathogen isolates falling into four sectors. A group of five isolates with high virulence, high absolute IPCA-1 scores, moderate IPCA-2 scores, low AMMI stability index '$D_i$' values and minimal deviations from additive main effects displayed in AMMI biplot as well as response plot, were identified as possessing stable pathogenicity across 16 host genotypes. The largest group of 27 isolates with low virulence, small IPCA-1 as well as IPCA-2 scores, low $D_i$ values and minimal deviations from additive main effect predictions, possessed stable pathogenicity for low virulence. The AMMI analysis and biplot display facilitated in a better understanding of the host-pathogen interaction, adaptability of pathogen isolates to specific host genotypes, identification of isolates showing stable pathogenicity and most discriminating host genotypes, which could be useful in location specific breeding programs aiming at deployment of resistant host genotypes in bacterial blight disease control strategies.

• Plant Disease and Agriculture
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• v.5 no.2
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• pp.69-76
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• 1999

Acidovorax avenae subsp. avenae is the causal pathogen of several hosts including oats corn foxtail millet wheatgrass sugarcane and rice. The pathogen is a seedborne pathogen of rice and known to occur widely in rice growing countries. The pathogen cause inhibition of germination brown stripe on the leaf curling of the leaf sheath and abnormal elongation of the mesocotyl of irce. Bacterial colonies grow slowly and are convex circular and creamy with tan to brown center. The causal baterium is Gram-negative and rod shape with a single polar flagellum Nonfluorescence poly-$\beta$-hydroxybutyrate accumulation and precipitate formation around the colony on the medium are useful in the differentiation of this bacterium from other subspecies of A. avenae as well as nonfluorescent bacteria pathogenic to rice. This bacterium has belonged to the genus of Psdeudomonas but recently was transferred to the new genus Acidovorax on the basis of bacteriological and molecular biological data. However the difference of biochemical characteristics protein profile of the cell and host range among strains should be more clarified. To develop an effective control strategy for this disease understanding of detailed life cycle of the disease ritical environmental factors affecting disease development on each host and relationship to grain discoloration of rice are prerequisite. Although the affected area has been world-widely reported there is on recent progress on the understanding of the bacteriological and ecological characteristics of the causal bacterium and control means of the disease.

• The Plant Pathology Journal
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• v.34 no.2
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• pp.126-138
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• 2018

Rice blast caused by Magnaporthe oryzae is a major disease. In the present study, we aimed to identify and evaluate the novel bacterial isolates from rice rhizosphere for biocontrol of M. oryzae pathogen. Sixty bacterial strains from the rice plant's rhizosphere were tested for their biocontrol activity against M. oryzae under in vitro and in vivo. Among them, B. amyloliquefaciens had significant high activity against the pathogen. The least disease severity and highest germination were recorded in seeds treated with B. amyloliquefaciens UASBR9 (0.96 and 98.00%) compared to untreated control (3.43 and 95.00%, respectively) under in vivo condition. These isolates had high activity of enzymes in relation to growth promoting activity upon challenge inoculation of the pathogen. The potential strains were identified based on 16S rRNA gene sequencing and dominance of these particular genes were associated in Bacillus strains. These strains were also confirmed for the presence of antimicrobial peptide biosynthetic genes viz., srfAA (surfactin), fenD (fengycin), spaS (subtilin), and ituC (iturin) related to secondary metabolite production (e.g., AMPs). Overall, the results suggested that application of potential bacterial strains like B. amyloliquefaciens UASBR9 not only helps in control of the biological suppression of one of the most devastating rice pathogens, M. grisea but also increases plant growth along with a reduction in application of toxic chemical pesticides.

• The Plant Pathology Journal
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• v.23 no.1
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• pp.22-25
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• 2007

Biocontrol activity of five strains of selected rhizo-bacteria were tested in tomato against bacterial wilt caused by Ralstonia solanacearum. After root bacterization the plants were grown in a perlite-hydroponic system. Upon challenge inoculation with the pathogen, all of the rhizobacterial strains efficiently suppressed the bacterial wilt in tomato in various rates, at maximum by the strain, Bacillus vallismortis strain EXTN-1. While the percent of infected plants in the non-bacterized control plants were 95%, it was only 65% in plants pre-treated with EXTN-1. It was also demonstrated that the movement of R. solanacearum within the stem was significantly hampered when the plants were root bacterized. As EXTN-1 has no antagonistic properties against R. solanacearum, the bacterial wilt was probably suppressed by a mechanism other than antibiosis. Previously, the strain had been proven to produce an efficient elicitor for inducing systemic resistance in many crops. As the present study confirmed that EXTN-1 has the ability for reducing the pathogen spread in tomato, the strain could be effectively used as a potential biocontrol agent against bacterial wilt.

• The Plant Pathology Journal
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• v.17 no.6
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• pp.336-341
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• 2001

The distribution of citrusphages and phage types of Xanthomonas axonopodis pv. citri was investigated in Korea. Forty-eight strains of the bacterial pathogen and 28 bacteriophage strains were isolated from citrus leaves showing the citrus canker symptom. Only a single bacteriophage group, named CPK, was identified based on their aggressiveness to the bacterial pathogen. The bacterial strains were differentiated into two Iysotypes based on their sensitivity to CPK. Lysotype I, which was sensitive to CPK, was more predominant (96%), while only 4% belonged to Iysotype II, which was resistant to CPK. Among the 13 xanthomonads including Iysotype A and Iysotype B of X axonopodis pv. citri, CPKs were only aggressive to BC 83 (=Xc 62) strain of X. axonopodis pv, citri reported as Iysotype A. Thus, bacterial pathogens and citrusphages related to citrus plants mainly distributed in Korea were presumed as Iysotype A of X. axonopodis pv, citri, and Iysotype A-infecting CP$_1$ respectively.