• The Plant Pathology Journal
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• 제38권1호
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• pp.25-32
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• 2022

Plant pathogens pose major threats on agriculture and horticulture, causing significant economic loss worldwide. Due to the continuous and excessive use of synthetic pesticides, emergence of pesticide resistant pathogens has become more frequent. Thus, there is a growing needs for environmentally-friendly and selective antimicrobial agents with a novel mode of action, which may be used in combination with conventional pesticides to delay development of pesticide resistance. In this study, we evaluated the potentials of lichen substances as novel biopesticides against eight bacterial and twelve fungal plant pathogens that have historically caused significant phytopathological problems in South Korea. Eight lichen substances of diverse chemical origins were extracted from axenic culture or dried specimen, and further purified for comparative analysis of their antimicrobial properties. Usnic acid and vulpinic acid exhibited strong antibacterial activities against Clavibacter michiganensis subsp. michiganensis. In addition, usnic acid and vulpinic acid were highly effective in the growth inhibition of fungal pathogens, such as Diaporthe eres, D. actinidiae, and Sclerotinia sclerotiorum. Intriguingly, the growth of Rhizoctonia solani was specifically inhibited by lecanoric acid, indicating that lichen substances exhibit some degrees of selectivity to plant pathogens. These results suggested that lichen substance can be used as a selective biopesticide for controlling plant disease of agricultural and horticultural significance, minimizing possible emergence of pesticide resistant pathogens in fields.

• 한국응용곤충학회지
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• 제50권3호
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• pp.171-178
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• 2011

Bacillus thuringiensis (Bt)는 나비목의 해충방제에 주로 사용되는 미생물농약이다. 그러나 파밤나방(Spodoptera exigua)과 배추좀나방(Plutella xylostella)에서 보듯 종령기에 접어들면 Bt 감수성이 현격하게 낮아져 방제효율이 낮아진다. 본 연구는 Bt의 병원력을 제고시키기는 데 목적을 두고, 이를 위해 곤충의 면역반응을 억제시키는 곤충병원세균의 대사물질을 이용하여 Bt의 혼합제를 개발하려 했다. 곤충병원세균(Xenorhabdus nematophila (Xn) 또는 Photorhabdus temperata ssp. temperata (Ptt))의 배양액을 다양한 농도로 Bt에 혼합하여 파밤나방과 배추좀나방 종령 유충에 처리하였을 때 Bt 병원력을 현격하게 증가시켰다. 세균 배양액으로부터 동정한 다섯 가지의 화합물을 Bt와 혼합하여 처리하면 Bt 병원력을 또한 증가시켰다. 최적의 방제 효과를 나타낼 수 있는 Bt와 세균배양액 또는 대사물질의 혼합비율과 살포량을 결정한 후 배추 포장에 발생한 배추좀나방과 파밤나방 종령 유충에 대해 처리하였다. Bt와 Xn 배양액을 2 회 이상 살포하면 배추좀나방과 파밤나방에 대해 100%의 방제효과를 나타냈으나, Bt 단독으로 처리하면 각각 약 80%와 60% 이하의 방제효과를 나타내었다. Ptt 배양액 및 세균 대사물질을 포함한 다른 Bt 혼합제들 또한 뚜렷한 병원력 증가를 간이포장실험에서 보여주었다. 이러한 Bt 혼합제를 통틀어 "비티플러스"라 명명하였으며, 이는 Bt 약효의 단점을 극복한 효과적 미생물 살충제로 개발 가능성을 보여주었다.

• Journal of Applied Biological Chemistry
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• 제55권2호
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• pp.123-127
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• 2012

오늘날 환경친화적인 생물농약을 개발하기 위한 미생물로는 Bacillus thuringiensis 이외에 Photorhabdus, Xenorhabdus 및 Serratia와 같은 곤충병원성 미생물과 Pseudomonas와 같은 식물유용 미생물에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 곤충병원성 미생물인 Photorhabdus temperata M1021 균주를 동결건조법을 이용하여 제제화 하였으며, 동결건조 시 세포보호를 위하여 skim milk, starch, sodium alginate, glucose와 sodium glutamate를 농도별로 첨가하여 동결 건조 후의 세포 생존율을 확인하였다. 그 결과 7% (w/v)의 skim milk가 첨가된 시료에서 가장 높은 63%의 생존율을 나타내었다. 제제화된 동결 건조균을 공기와 접촉시키면서 저온에서 생존율을 측정한 결과 4주 후에도 75% 이상의 생존율을 나타내었다. 또한 제제를 이용한 살충력 시험에서 꿀벌 부채명나방 유충에 대한 주사독성은 $2.0{\times}10^1$ cells/lavar 이상을 주사할 경우 4일 이내에 전체유충이 사멸하는 것으로 나타났으며, $2.0{\times}10^0$ cells/larva의 아주 낮은 농도에서도 50% 이상의 유충사멸 효과를 확인하였다. 본 연구에서 사용된 P. temperata M1021 균주의 동결건조 분말의 뛰어난 살충효과는 보다 현실적인 생물학적 제제로의 개발가능성을 제시하고 있다.

• 한국환경농학회지
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• 제35권3호
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• pp.211-215
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• 2016

BACKGROUND: The commercial biopesticides containing Chenopodium ambrosioides L. extracts which have been registered as one of the ingredients of the commercial biopesticide by the organic agriculture materials, and have been widely used in Republic of Korea. However, the quantitative analysis method of the active substances for the commercial biopesticides containing C. ambrosioides L. extract has not been conducted.METHODS AND RESULTS: To analyze the quantitative analysis of ascaridole, carvacrol, and p-cymene as active substances of C. ambrosioides L. extract, hydrophilic lipophilic balance cartridge was used for solid phase extraction. The active substances were analyzed by the gas chromatography with flame ionization detector. The limit of quantitation values of ascaridole, carvacrol, and p-cymene were 10, 5, and 2 mg/L, and the recovery rates were 96.3, 84.0, and 82.5% in liquid products and 98.3, 99.1, and 97.3% in solid products, respectively. The total content of ascaridole, carvacrol, and p-cymene in the commercial biopesticides was ranged from 0.08 to 12.75%.CONCLUSION: From these results, this method was suitable for the quantitative analysis of the active substances of commercial biopesticides containing C. ambrosioides L. extract.

• KSBB Journal
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• 제29권3호
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• pp.131-138
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• 2014

In this study, we isolated two novel chitinase producing bacterial strains from yellow loess samples collected from Jullanamdo province. The chitinase producing bacteria were isolated based on the zone size of clearance in the chitin agar plates. Both of them were gram positive, rod ($2{\sim}3{\times}0.3{\sim}0.4{\mu}m$), spore-forming, and motility positive. They were facultative anaerobic, catalase positive and hydrolyzed starch, gelatin, and casein. From the 16s rRNA gene sequence analysis, the isolates were labeled as Bacillus licheniformis KYLS-CU01 and B. licheniformis KYLS-CU02. The isolates showed higher extracellular chitinase activities than B. licheniformis ATCC 14580 as a control. The optimum temperature and pH for chitinase production were $40^{\circ}C$ and pH 7.0, respectively. Response Surface Methodology (RSM) was used to optimize the culture medium for efficient production of the chitinase. Under this optimal condition, 1.5 times higher chitinase activity of B. licheniformis KYLS-CU02 was obtained. Extracellular chitinases of the two isolates were purified through ammonium sulfate precipitation and anion-exchange DEAE-cellulose column chromatography. The specific activities of purified chitinase from B. licheniformis KYLS-CU01 and B. licheniformis KYLS-CU02 were 7.65 and 5.21 U/mg protein, respectively. The molecular weights of the two purified chitinases were 59 kDa. Further, the purified chitinase of B. licheniformis KYLS-CU01 showed high antifungal activity against Fusarium sp.. In conclusion, these two bacterial isolates can be used as a biopesticide to control pathogenic fungi.

• 한국환경농학회지
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• 제34권3호
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• pp.217-222
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• 2015

BACKGROUND: Garlic (Allium sativum) contains polyphenols and sulfur compounds that are recognized as antioxidant, antithrombotic, anticancer, antibacterial, antimicrobial, nematicidal, and insecticidal activity. For this reason, the Environmentally-friendly Agriculture Promotion Act allowed the garlic extract as commercial biopesticide material for crop protection, nine commercial biopesticides containing A. sativum extract have been marketed in Korea. METHODS AND RESULTS: The determination of allylmethyl sulfide (AMS), dimethyl disulfide (DMDS), and dipropyl sulfide (DPS) in biopesticides containing A. sativum extract was developed and validated by gas chromatography (GC) mass spectrometry (MS) with head-space sampler. The developed method was validated, and the limit of quantification (LOQ) and recovery rates of AMS, DMDS, and DPS were 0.08, 0.32, and 0.09 mg/L and 90.3-91.3, 86.2-88.3, and 87.6-89.5%, respectively. From the nine commercial biopesticide samples, contents of AMS, DMDS, and DPS were analyzed using the developed method and results showed

• Journal of Applied Biological Chemistry
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• 제59권2호
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• pp.165-169
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• 2016

The quantitative analytical method for the bioactive substance, 3-cyano-4-methoxy-N-methyl-2-pyridone (ricinine) and an index compound, ricinoleic acid in castor plant (Ricinus communis) extract or oil was developed. For the determination of a pyridone alkaloid compound, ricinine, successive cartridge cleanup method combined with ultra-performance liquid chromatography was set up with $ENVI-Carb^{TM}$ (0.5 g) and $C_{18}$ SPE cartridges. Accuracy and precision were evaluated through fortification studies of one biopesticide (PE) at 10 and $100mg\;kg^{-1}$. Mean recoveries of ricinine were 98.7 and 96.0 % associated with less than 10 % RSD, respectively. For the determination of ricinoleic acid in castor extract and oil, saponification and methylation were optimized using gas chromatography-time of flight mass spectrometry. Recovery was more than 84.8 % associated with 6.2 % RSD after derivatization procedure. Both methodologies developed were applied to analyze real samples including three castor oil products and six commercially available biopesticides containing R. communis, collected at Korean market. The contents of ricinine and ricinoleic acid in most commercial biopesticides were less than the oil or extract contents indicated by label.

• International Journal of Industrial Entomology and Biomaterials
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• 제1권2호
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• pp.177-181
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• 2000

Spilarctia obliqua(Wlk.) is a serious pest of mulberry which is naturally affected by its nucleopolyhedrosis virus (SoNPV) in field conditions. The polyhedral occlusion bodies (POB's) were hexahedron under scanning and transmission electron microscope and measured 0.42${\mu}{\textrm}{m}$ to 0.67 ${\mu}{\textrm}{m}$ in diameter. The symptoms of NPV infected S. obliqua larvae resembled with that of other NPVs' infected lepidopterous larvae. The pathogenicity and potentiality of this virus against S. obliqua was tested in the laboratory conditions and the results showed 100% mortality in larvae inoculated with SoNPV at 6.23${\times}10^5$ POBs/ml. Therefore, SoNPV appears to have a high potential as a microbial biocontrol agent against S. obliqua larvae.

• KSBB Journal
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• 제14권2호
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• pp.198-204
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• 1999

Asymbiotic bacterium with highly effective toxins was isolated from entomopathogenic nematode Steinernema glaseri which has been widely used against various soil-inhabiting pests. The symbiont of S. glaseri was identified as Xenorhabdus nematophilus sp. by using several biochemical and physiological tests. When this strain was released into the hemolymph of insect larva, it produced highly toxic substances and killed the larva within 2 days. Two colony forms that differed n some biochemical characteristics were observed when cultures in vitro. Phase l colonies were mucid and difficult to be dispersed in liquid. Phase II was not mucoid and was easily dispersed in liquid. It did not adsorb neutral red or bromothymol blue. Rod-shaped cell size was highly variable between two phases, ranging 2-10 ${\mu}{\textrm}{m}$. It was also found that only infective-stage nematodes can carry only primary-phase Xenorhabdus in their intestine.

• 식물병연구
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• 제20권3호
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• pp.216-218
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• 2014

Lysobacter antibiocus HS124 is a chitinase-producing rhizobacterium with proven capacities to suppress plant diseases. Bacterial cultures of L. antibioticus HS124 showed strong biocontrol efficacies against various plant diseases compared to those of bacterial cultures of Bacillus subtilis QST713 which is an active ingredient of a commercial biopesticide, Serenade. Here, we report the draft genome sequence and automated annotation of strain HS124. This draft genome sequence indicates the novelty of L. antibiocus HS124 and a subset of gene functions that may be related to its biocontrol activities.