• The Plant Pathology Journal
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• 제22권3호
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• pp.278-282
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• 2006

Bacillus vallismortis EXTN-1, a biocontrol agent in cucumber, tomato and potato was tested in rice pathosystem against rice fungal pathogens viz. Magnaporthe grisea, Rhizoctonia solani and Cochliobolus miyabeanus. Apart from increasing the yield in the bacterized plants (11.6-12.6% over control), the study showed that EXTN1 is effective in bringing about disease suppression against all the tested fungal pathogens. EXTN-l treatment resulted in 52.11% reduction in rice blast, 83.02% reduction in sheath blight and 11.54% decrease in brown spot symptoms. As the strain is proven as an inducer for systemic resistance based on PR gene expression in Arabidopsis and tobacco models, it is supposed that a similar mechanism works in rice, bringing about disease suppression. The strain could be used as a potent biocontrol and growth-promoting agent in rice cropping system.

• The Plant Pathology Journal
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• 제22권4호
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• pp.360-363
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• 2006

Efficacy of plant growth promoting rhizobacteria(PGPR) Bacillus vallismortis strain EXTN-1 has been proved in eliciting induced systemic resistance(ISR) in several crops. The present paper described the beneficial effects of EXTN-1 in potato as increase in yield and chlorophyll content, and plant protection against Potato Virus Y and X(PVY & PVX). EXTN-1 induced systemic resistance to the plants resulting in significant disease suppression in the field. Also the plants under treatment with EXTN-1 had higher chlorophyll content. The bacterized plants had significantly higher yields over the untreated control plants. The strain induced activation of defense genes, PR-1a and PDF 1.2 in transgenic tobacco model, which indicated the possible role of both SA, and JA pathways in EXTN-1 mediated plant protection against crop diseases.

• 농약과학회지
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• 제17권4호
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• pp.388-393
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• 2013

Bacillus vallismortis strain EXTN-1은 근권세균으로써 생육촉진 효과와 함께 광범위한 식물 병 방제효과가 보고되어있다. 본 연구에서 EXTN-1으로부터 방출되는 휘발성 유기 화합물도 식물의 생육촉진과 방어시스템에 관여를 하는지 확인하기 위해 수행되었다. I-plate 시스템에서 각기 다른 배지(TSA, LBA, NA, KBA, PDA)에 EXTN-1을 배양하였을 때, KBA배지에서 가장 높은 생육촉진현상이 확인되었고 TSA, LBA, NA, PDA 배지에서도 생육촉진을 확인할 수 있었다. 생육촉진 현상에 $CO_2$가 관여 할 수 있지만 TSA, PDA, LBA의 배지에서는 $CO_2$와의 관계없음을 확인 할 수 있었다. SPME-GC/MS를 이용해 휘발성 유기화합물을 확인한 결과, 가장 많이 방출되는 휘발성 유기화합물은 3-Hydroxy-2- butanone으로 각 농도 (10 ppm~0.001 ppm)에서 생육차이와 발병도를 확인하였다. 1 ppm에서 생육은 무처리에 비해 2.6배 증가한 반면에 0.001 ppm에서 1.2배로 가장 적게 증가하였고 발병도는 10 ppm에서 46%, 0.001 ppm에서 65%로 가장 높게 발병되었지만 무처리(91%)에 비해 낮았다. 이러한 효과는 EXTN-1으로부터 방출되는 휘발성 유기 화합물이 식물의 생육촉진과 병에 대한 저항성 발현에 관여한다고 볼 수 있다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2005년도 국제학술회의
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• pp.140-141
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• 2005

• 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.

• 식물병연구
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• 제21권4호
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• pp.255-260
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• 2015

We investigated influence of three commercial antibiotics viz., oxolinic acid, streptomycin, and validamycin A, on biocontrol and plant growth promoting activities of Bacillus vallismortis EXTN-1 and BS07M in Chinese cabbage. Plants were pre-drenched with these strains followed by antibiotics application at recommended and ten-fold diluted concentration to test the effect on biocontrol ability against soft rot caused by Pectobacterium carotovorum SCC1. The viability of the two biocontrol strains and bacterial pathogen SCC1 was significantly reduced by oxolinic acid and streptomycin in vitro assay, but not by validamycin A. In plant trials, strains EXTN-1 and BS07M controlled soft rot in Chinese cabbage, and there was a significant difference in disease severity when the antibiotics were applied to the plants drenched with the two biocontrol agents. Additional foliar applications of oxolinic acid and streptomycin reduced the disease irrespective of pre-drench treatment of the PGPRs. However, when the plants were pre-drenched with EXTN-1 followed by spray of validamycin A at recommended concentration, soft rot significantly reduced compared to untreated control. Similarly, strains EXTN-1 and BS07M significantly enhanced plant growth, but it did not show synergistic effect with additional spray of antibiotics. Populations of the EXTN-1 or BS07M in the rhizosphere of plants sprayed with antibiotics were significantly affected as compared to control. Taken together, our results suggest that the three antibiotics used for soft rot control in Chinese cabbage could affect bacterial mediated biocontrol and plant growth promoting activities. Therefore, combined treatment of the PGPRs and the commercial antibiotics should be carefully applied to sustain environmental friendly disease management.

• The Plant Pathology Journal
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• 제25권3호
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• pp.263-269
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• 2009

Bacterial wilt, Fusarium wilt and Foot rot caused by Ralstonia solanacearum, Fusarium oxysporum, and Phytophthora capsici respectively, continue to be severe problems to tomato, potato and black pepper growers in Vietnam. Three bio-products, Bacillus vallismortis EXTN-1 (EXTN-1), Bacillus sp. and Paenibacillus sp. (ESSC) and Bacillus substilis (MFMF) were examined in greenhouse bioassay for the ability to reduce bacterial wilt, fusarium wilt and foot rot disease severity. While these bio-products significantly reduced disease severities, EXTN-1 was the most effective, providing a mean level of disease reduction 80.0 to 90.0% against bacterial wilt, fusarium wilt and foot rot diseases under greenhouse conditions. ESSC and MFMF also significantly reduced fusarium wilt, bacterial wilt and foot rot severity under greenhouse conditions. Bio-product, EXTN-1 with the greatest efficacy under greenhouse condition was tested for the ability to reduce bacterial wilt, fusarium wilt and foot rot under field condition at Song Phuong and Thuong Tin locations in Ha Tay province, Vietnam. Under field condition, EXTN-1 provided a mean level of disease reduction more than 45.0% against all three diseases compared to water treated control. Besides, EXTN-1 treatment increased the yield in tomato fruits 17.3% than water treated control plants.

• The Plant Pathology Journal
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• 제39권1호
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• pp.123-135
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• 2023

Previously, Pseudomonas plecoglossicida YJR13 and Pseudomonas putida YJR92 from a sequential screening procedure were proven to effectively control Phytophthora blight caused by Phytophthora capsici. In this study, we further investigated the anti-oomycete activities of these strains against mycelial growth, zoospore germination, and germ tube elongation of P. capsici. We also investigated root colonization ability of the bacterial strains in square dishes, including cell motility (swimming and swarming motilities) and biofilm formation. Both strains significantly inhibited mycelial growth in liquid and solid V8 juice media and M9 minimal media, zoospore germination, and germ tube elongation compared with Bacillus vallismortis EXTN-1 (positive biocontrol strain), Sphingomonas aquatilis KU408 (negative biocontrol strain), and MgSO₄ solution (untreated control). In diluted (nutrient-deficient) V₈ juice broth, the tested strain populations were maintained at >10⁸ cells/ml, simultaneously providing mycelial inhibitory activity. Additionally, these strains colonized pepper roots at a 10⁶ cells/ml concentration for 7 days. The root colonization of the strains was supported by strong swimming and swarming activities, biofilm formation, and chemotactic activity towards exudate components (amino acids, organic acids, and sugars) of pepper roots. Collectively, these results suggest that strains YJR13 and YJR92 can effectively suppress Phytophthora blight of pepper through direct anti-oomycete activities against mycelial growth, zoospore germination and germ tube elongation. Bacterial colonization of pepper roots may be mediated by cell motility and biofilm formation together with chemotaxis to root exudates.

• 식물병연구
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• 제15권3호
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• pp.230-235
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• 2009

배 저장 중 신고에서 발생되는 과피얼룩 및 부패증상의 발생억제를 위해 2년간 시험한 결과 수확 후 약제 또는 생물제제 살포로 발병을 억제할 수 있었으며, 살포시기가 늦어질수록 발병가능성은 높은 것으로 나타났다. 한편, 처리시기와 관련하여 과실 수확 후 6주 또는 그 이후 처리는 상처부위의 부패 발생 억제효과가 낮았다. 그러나 TBZ를 수확 3~6주에 처리시 저장중 과피얼룩 및 부패과 발생은 현저히 억제되었다. 또한, TBZ, Fludioxonil과 Pyrimethanil 처리에 의한 과피얼룩 및 부패과 발생은 상처접종 처리에서 최대 14일까지 발병이 억제되었다. 그리고 수확시 TBZ 및 3주 후 Fludioxonil 처리는 수확시 TBZ 단용처리보다 발병억제력이 높았다. 한편, 2종의 생물제제(EXTN-1, Bio-Save 110)는 C. tenuissimum 접종처리에서 저장 14일까지 발병을 억제하여 저장 유통중 발생하는 상처부위 발병 억제가 가능 할 것으로 판단되었다. 결론적으로 저장 중 과피얼룩 및 부패방제를 위해 서로 다른 약제조합을 수확 후 저장 전에 처리할 때 가장 높은 방제효과를 얻을 수 있었다.