• The Plant Pathology Journal
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• 제33권2호
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• pp.170-183
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• 2017

Bacterial fruit blotch (BFB), which is caused by Acidovorax citrulli, is a serious threat to watermelon growers around the world. The present study was conducted to screen effective rhizobacterial isolates against 35 different A. citrulli isolates and determine their efficacy on BFB and growth parameters of watermelon. Two rhizobacterial isolates viz. Paenibacillus polymyxa (SN-22), Sinomonas atrocyanea (NSB-27) showed high inhibitory activity in the preliminary screening and were further evaluated for their effect on BFB and growth parameters of three different watermelon varieties under greenhouse conditions. The greenhouse experiment result revealed that SN-22 and NSB-27 significantly reduced BFB and had significant stimulatory effect on total chlorophyll content, plant height, total fresh weight and total dry weight compared to uninoculated plants across the tested three watermelon varieties. Analysis of the 16S ribosomal RNA (rRNA) sequences revealed that strains SN-22 belong to P. polymyxa and NSB-27 to S. atrocyanea with the bootstrap value of 99% and 98%, respectively. The isolates SN-22 and NSB-27 were tested for antagonistic and PGP traits. The result showed that the tested isolates produced siderophore, hydrolytic enzymes (protease and cellulose), chitinase, starch hydrolytic enzymes and they showed phosphate as well as zinc solubilizing capacity. This is the first report of P. polymyxa (SN-22) and S. atrocyanea (NSB-27) as biocontrol-plant growth promoting rhizobacteria on watermelon.

• 한국미생물·생명공학회지
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• 제31권4호
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• pp.421-428
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• 2003

길항미생물을 이용한 항곰팡이성 퇴비의 개발을 목적으로 공시 식물로써 Spinacia oleracea L과 식물 병원균 Rhizoctonia solani Kuhn O-28을 모델로 사용하여 수행 되었다. 다양한 음식쓰레기를 일년동안 숙성시킨 퇴비로부터 80 균주를 분리하였고, 그 중 No.15-2 균주가 R. solani Kuhn O-28에 대해 가장 높은 항곰팡이 활성을 보였다. 16S rDNA sequencing과 primer pair PCR에 의해 표현형과 분류학적으로 거의 독성이 없는 것으로 밝혀진 Burkholderia cepacia genomoval V로 분류되었다. 이 B. cepacia No. 15-2가 퇴비화 중에 우점하였으며 그 균수는 15일 동안 거의 $10^{13}$ cfu/g을 유지하였다. S. oleracea L을 배양 했을 경우 R. solani Kuhn O-28에 의한 발병율은 B. cepacia No.15-2를 첨가함으로써 40% 감소하였다. 결론적으로 B. cepacia No.15-2는 다양한 식물의 곰팡이 유래의 병을 방제하는 데 이용 가능할 것으로 사료된다.

• The Plant Pathology Journal
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• 제32권3호
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• pp.228-241
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• 2016

In our previous study, we reported that a novel endophytic bacterium Bacillus oryzicola YC7007 has suppressed bacterial diseases of rice via induced systemic resistance and antibiotic production. This endophytic strain, B. oryzicola YC7007 was used as a biological control agent against bakanae disease of rice caused by Fusarium fujikuroi, and its mechanism of interaction with the pathogen and the rice was further elucidated. Root drenching with B. oryzicola YC7007 suspension reduced the disease severity of bakanae significantly when compared with the untreated controls. The treatments of B. oryzicola YC7007 suspension ($2.0{\times}10^7cfu/ml$) to the rice rhizosphere reduced bakanae severity by 46-78% in pots and nursery box tests containing autoclaved and non-autoclaved soils. Moreover, in the detached rice leaves bioassay, the development of necrotic lesion and mycelial expansion of F. fujikuroi were inhibited significantly by spraying the culture filtrate of B. oryzicola YC7007. Drenching of ethyl acetate extracts of the culture filtrate to the rhizosphere of rice seedlings also reduced the bakanae disease severity in the plant culture dish tests. With the root drenching of B. oryzicola YC7007 suspension, the accumulation of hydrogen peroxide was observed at an early stage of rice seedlings, and a hormonal defense was elicited with and without pathogen inoculation. Our results showed that the strain B. oryzicola YC7007 had a good biocontrol activity against the bakanae disease of rice by direct inhibition, and was also capable of inducing systemic resistance against the pathogen via primed induction of the jasmonic acid pathway.

• 한국환경농학회지
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• 제28권3호
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• pp.289-294
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• 2009

사과 재배에 피해를 주고 있는 사과 겹무늬썩음병, 탄저병, 라이족토니아병을 복합적으로 방제하기 위한 기초연구로서 각 병원균에 대하여 우수한 길항력을 동시에 가지는 길항미생물을 선발하고 Streptomyces sp. S-1110으로 동정하였다. 분리된 길항미생물은 배양상등액으로 길항물질을 분비하였으며 우수한 열안정성과 pH 안정성을 가지는 특성이 있었으며 각 병원균에 대한 감수성이 조금씩 달라서 2 종 이상의 길항물질이 동시에 생산되어 길항작용을 하는 것으로 추정되었다. 또한 분리균이 생산하는 길항물질을 사과 과실에 직접접종된 사과 겹무늬썩음병과 탄저병의 방제를 위해 실험한 결과 높은 방제력을 보였다. 따라서 분리된 길항미생물은 사과 과수원 및 저장소에서 동시에 수종의 질병방제에 쓰일 수 있는 천연 복합방제제의 개발을 위한 기초 균주로의 가치가 높은 것으로 판단된다.

• 한국미생물·생명공학회지
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• 제32권4호
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• pp.312-316
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• 2004

토양 우점능이 강한 생물학적 방제제 제조를 위해 경북지역 토양에서 길항균주를 분리하고 이들 중 Fusarium oxysporum, Phytophthora capsici 에 강력한 길항능을 보이는 Pseudomonas sp. 4059 를 선발, 동정하였다. Pseudomonas sp. 4059 의 시들음 병균 Fusarium oxysporum, 고추 역병균 Phytophthora capsici 에 대한 길항기작은 내열성 저분자의 항생물질과 철이온을 특이적으로 흡착하는 siderophore의 생산에 의한 것이다. Pseudomonas sp. 4059 는 항진균성 항생물질 Phenazine 생산 유전자를 소유하며 Salkowski test에 양성인 옥신류 생산도 한다는 것을 확인하였다. Pseudomonas sp. 4059 는 bioochemical tests, API test, MicroLogTM system을 통해 Pseudomonas fluorescens (biotype A)으로 98% 상동성을 보였으므로 이를 Pseudomonas fluorescens (biotype A) 4059 로 명명하였다. 선발된 길항균 Pseudomonas fluorescens (biotype A) 4059는 고추를 기주식물로 하였을 때 고추역병균인 Phytophthora capsici가 원인이 되는 고추역병을 in vivo 상에서도 충분히 억제할 수 있는 생물방제능을 나타내었다.

• The Plant Pathology Journal
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• 제31권1호
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• pp.50-60
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• 2015

The use of novel isolates of Trichoderma with efficient antagonistic capacity against Fusarium oxysporum f. sp. lycopersici (FOL) is a promising alternative strategy to pesticides for tomato wilt management. We evaluated the antagonistic activity of 30 isolates of T. asperellum against 4 different isolates of FOL. The production of extracellular cell wall degrading enzymes of the antagonistic isolates was also measured. The random amplified polymorphic DNA (RAPD) method was applied to assess the genetic variability among the T. asperellum isolates. All of the T. asperellum isolates significantly reduced the mycelial growth of FOL isolates but the amount of growth reduction varied significantly as well. There was a correlation between the antagonistic capacity of T. asperellum isolates towards FOL and their lytic enzyme production. Isolates showing high levels of chitinase and ${\beta}$-1,3-glucanase activities strongly inhibited the growth of FOL isolates. RAPD analysis showed a high level of genetic variation among T. asperellum isolates. The UPGMA dendrogram revealed that T. asperellum isolates could not be grouped by their antagonistic behavior or lytic enzymes production. Six isolates of T. asperellum were highly antagonistic towards FOL and potentially could be used in commercial agriculture to control tomato wilt. Our results are consistent with the conclusion that understanding the genetic variation within Trichoderma isolates and their biochemical capabilities are required for the selection of effective indigenous fungal strains for the use as biocontrol agents.

• The Plant Pathology Journal
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• 제23권1호
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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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• 제26권4호
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• pp.353-359
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• 2010

In order to control postharvest spoilage of satsuma mandarin fruits, rhizobacteria were isolated from soil samples. The Pantoea agglomerans strain 59-4 (Pa 59-4) which suppresses the decay of mandarin fruit by green and blue mold, was tested for the control efficacy and its mode of action was investigated. Pa 59-4 inhibited infection by green and blue mold on wounded mandarins, which were artificially inoculated with a spore suspension of Penicillium digitatum and P. italicum with control efficacies of 85-90% and 75-80%, respectively. The biocontrol efficacy was increased by raising the concentration of cells to between $10^8$ and $10^9\;cfu/ml$, and pretreatment with the antagonist prevented subsequent infection by green mold. The population of Pa 59-4 was increased more than 10 fold during the 24 hr incubation at $20^{\circ}C$, indicating that colonization of the wound site might prevent the infection by green mold. Despite poor antifungal activity, the Pa 59-4 isolate completely inhibited the germination and growth of P. digitatum spores at $1{\times}10^8\;cfu/ml$. We argue that the control efficacy was mediated by nutrient competition. Overall, the effective rhizobacterium, Pa 59-4, was shown to be a promising biocontrol agent for the postharvest spoilage of mandarin fruits by green and blue mold.

• 미생물학회지
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• 제53권4호
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• pp.351-353
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• 2017

토마토 뿌리에서 분리한 Chryseobacterium sp. T16E-39 균주는 식물생육촉진과 역병, 시들음병에 대한 억제효과가 있었다. 이 균주의 유전체 염기서열은 4,873,888 염기쌍이었으며 G + C 함량은 35.22%이었다. 이 유전체는 4,289개 단백질 유전자, 15개 rRNA 유전자, 71개 tRNA 유전자를 포함하였다. T16E-39 균주의 유전체에서 인산가용화, 식물호르몬 조절, 항산화 활성, 키틴 분해, 제9형 분비시스템에 관여하는 유전자를 확인하였으며, 이들 유전자는 식물의 생육을 촉진하고 병발생을 억제하는 기작과 관련되어 있을 것으로 판단된다.

• 식물병연구
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• 제13권2호
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• pp.93-97
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• 2007

비경작 산림 토양으로부터 고추 역병균과 탄저병균에 대한 항균활성, 불용태 인산의 가용화 및 식물체 초기생육촉진 효과를 보이는 방선균을 분리하였다. 선발된 미생물의 16S rDNA 염시서열을 분석한 결과, Streptomyces sp.로 동정되었다. Streptomyces sp. MG 121 균주는 고추열매를 이용한 역병과 탄저병을 80% 이상 억제하였다. MG 121균주 배양액의 식물체 엽면살포는 식물체의 초기생육을 10% 이상 촉진시키는 것으로 나타났다. 불용태 인산의 가용화 활성을 측정한 결과, 유리인산의 농도는 144시간 후 $762{\mu}g/ml$까지 증가하였다.