• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.1
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• pp.35-43
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• 2011

Thirty five isolates of Trichoderma species collected from seven different locations of Bangladesh were studied for morphological characters and molecular variation. Mycelial diameters of the isolates varied from 8.28 cm to 9.00 cm. Based on colony colour, isolates were grouped into five such as dark green, green, light green, yellowish green and whitish green. Maximum isolates were green and light green. On the basis of growth habit and colony consistency, the isolates were categorized into three groups, in which most species had fast growth and were compact in appearance. PCR-based Random Amplified Polymorphic DNA (RAPD) technique employing 3 decamer primers produced 36 scorable bands of which all (100%) were polymorphic. The co-efficient of gene differentiation (Gst) was 1.0000 reflecting the existence of high level of genetic diversity among the isolates. The Unweighted Pair Group Method of Arithmetic Means (UPGMA) dendrogram constructed from Nei's (1972) genetic distance produced 2 main clusters (13 isolates in cluster 1 and 22 isolates in cluster 2). The result indicating their genetic diversity has opened new possibility of using the most efficient and more isolates of Trichoderma in the preparation of biopesticide and decomposition of municipality waste.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2159-2170
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• 2016

Many plant-pathogenic bacteria are dependent on quorum sensing (QS) to evoke disease. In this study, the population of QS and quorum quenching (QQ) bacteria was analyzed in a consecutive monoculture system of Pseudostellaria heterophylla. The isolated QS strains were identified as Serratia marcescens with SwrIR-type QS system and exhibited a significant increase over the years of monoculture. Only one QQ strain was isolated from newly planted soil sample and was identified as Bacillus thuringiensis, which secreted lactonase to degrade QS signal molecules. Inoculation of S. marcescens to P. heterophylla root could rapidly cause wilt disease, which was alleviated by B. thuringiensis. Furthermore, the expression of lactonase encoded by the aiiA gene in S. marcescens resulted in reduction of its pathogenicity, implying that the toxic effect of S. marcescens on the seedlings was QS-regulated. Meanwhile, excess lactonase in S. marcescens led to reduction in antibacterial substances, exoenzymes, and swarming motility, which might contribute to pathogensis on the seedlings. Root exudates and root tuber extracts of P. heterophylla significantly promoted the growth of S. marcescens, whereas a slight increase of B. thuringiensis was observed in both samples. These results demonstrated that QS-regulated behaviors in S. marcescens mediated by root exudates played an important role in replanting diseases of P. heterophylla.

• Korean Journal of Environmental Agriculture
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• v.36 no.1
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• pp.17-21
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• 2017

BACKGROUND: Castor oil and wormseed extract are important active ingredients for biopesticide, and ricinoleic acid in castor oil and three monoterpenes (ascaridole, carvacrol and p-cymene) in wormseed extract are known bioactive substances. However, their stabilities had not been studied, even though the stability was the core property for estimation of shelf-life of biopesticide. Aimed to investigate the thermal stabilities of the bioactive substances in castor oil and wormseed extracts. METHODS AND RESULTS: The contents of ricinoleic acid and three monoterpenes (ascaridole, carvacrol and p-cymene) were analyzed by gas chromatography (GC). The thermal stabilities of the bioactive substance were measured at $0^{\circ}C$, $23^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$, $45^{\circ}C$ and $54^{\circ}C$ for 84 d. The half-lives of ricinoleic acid in biopesticides was ranged from 28.9 d to 57.8 d at $30^{\circ}C$, and the stability of pure castor oil were located in the range ($t_{1/2}$=46.2d for Indian product and 27.7 d for Korean product) at the same temperature. The half-lives of the total monoterpenes in biopesticides were ranged from 3.9 d to 27.7 d at $30^{\circ}C$. Among the monoterpenes, the stability ascaridole and p-cymene were decreased in acidic condition. All the bioactive substances showed similar stability on the different thermal conditions. CONCLUSION:The half-lives of most bioactive substance from castor oil and wormseed extracts were less than 100 d. To increase the stability of bioactive substance in biopesticide, stabilizing additives like antioxidant and oxygen remover should be considered to extend of the shelf-life.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2004.10a
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• pp.21-21
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• 2004

• Environmental Analysis Health and Toxicology
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• v.18 no.2
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• pp.131-136
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• 2003

Anti-fungal materials producing bacteria were isolated from soil by bennett's agar and actinomycete isola-tion agar medium. The bacterla were identified as synonym of Actinomycetes. Based on the data obtained from its morphological and colony characteristics. The medium for production of anti-fungal materials was YEME (yeast extract 4 g, malt extract l0g, glucose 4 g, D.W 1ι, pH 7.0${\pm}$0.2). The culture conditions were 30$^{\circ}C$, 7 days and 200 rpm in shaking incubator. No. 13, No. 15 and No.28 strains were produced anti-fungal materials against fungal plant pathogens. Specially, The No. 28 strain showed a powerful biopesticide activity and broad spectrum effects of anti -fungal materials on Collectrichum coccodes, Botrytis cinerea, Cladosporium cucumerinum, Didymella bryoniae.

• Journal of Life Science
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• v.14 no.6 s.67
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• pp.1003-1008
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• 2004

11 plant essential oils are screened in vitro for their antifungal activities against Botrytis cinerea, Fusarium oxysporum and Rhizoctonia solani, which are causative agents of serious plant diseases. The radial growth of the test fungi were reduced in response to the oils. Among them, the essential oil from the bark of Cinnamomum zeylanicum inhibited 3 tested fungi growth, strongly, followed by those of oregano and thyme. The major constituents of the three essential oils, cinnaldehyde, carvacrol and thymol were tested for their effects on the fungi. From the results obtained, cinnamaldehyde, the major constituents of C. zeylanicum bark esential oil, has potential to be developed as a biopesticide for controlling phytopathogenic fungi causing serious damages on the important crops cultivated in Korea.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.96-104
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• 2019

Beauveria bassiana, one of the most common entomopathogenic fungi, has been isolated, pre defined and characterized in-house from soil of tea cultivation area. Experiments have been performed to verify the presence of chitinase as intracellular metabolite and its release as extracellular product rendering the spores with biopesticide activity. Although there are many responsible enzymes for the pest killer action of B. bassiana, binding property of chitinase depending on presence as well as absence of serine supplemented in the media has been studied with respect to the production and kinetics. A programmed investigation conclusively indicates that the isolated spore (hyphae) of B. bassiana has been metabolically enriched with the enzyme chitinase in presence of an externally added amino acid serine with its inhibitory kinetics.

• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.381-387
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• 2014

BACKGROUND: Garlic (Allium sativum) extract has been allowed as commercial biopesticide material for pesticidal activity in the Environmentally-friendly Agriculture Promotion Act. Nine commercial biopesticides containing A. sativum extract have been marketed in Korea. However, the analytical method of the active substances in these materials has not been studied. METHODS AND RESULTS: Cartridge clean-up method for the determination of dimethyl disulfide(DMDS), diallyl disulfide(DADS), and diallyl trisulfide(DATS) in biopesticides containing A. sativum extract was developed and validated by gas chromatography(GC). The clean-up method was optimized using hydrophilic lipophilic balance (HLB) solid phase extraction(SPE) cartridges for the bioactive sulfides in biopesticides containing A. sativum extract, and the eluate was analyzed to quantify the DMDS, DADS, and DATS using the GC. The developed method was validated, and the LOQ and recovery rates of DMDS, DADS, and DATS were 0.226, 0.063, and $0.051mg\;L^{-1}$ and 80.6, 84.8, and 73.1%, respectively. From the nine commercial biopesticide samples, contents of DMDS, DADS, and DATS were analyzed using the developed method and results showed $2.3mg\;L^{-1}$, respectively. CONCLUSION: The developed method could be used in determining the quality of biopesticides for the manufacture of commercial biopesticides containing A. sativum extract.

• Korean Journal of Environmental Agriculture
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• v.34 no.1
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• pp.52-56
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• 2015

BACKGROUND: Three commercial biopesticides containing derris extract, which is permitted as a commercial biopesticide substances by the Environmentally-friendly Agriculture Promotion Act, have been marketed in Korea. But, the quantitative analytical method of active substances for crop protection in biopesticides containing derris extract has not known. METHODS AND RESULTS: Solid phase extraction (SPE) cartridge clean-up method for the quantitative analysis of rotenone and deguelin in biopesticides containing derris extract was developed and validated by ultra-performance liquid chromatography (UPLC). The clean-up method was established using hydrophilic lipophilic balance (HLB) SPE cartridges for the bioactive substances in biopesticides containing derris extract, and the eluate was analyzed to quantify the rotenone and deguelin by the UPLC. LOQ and recovery rates of rotenone and deguelin were 0.085 and 0.044 mg/L, 95.7 and 93.3%, respectively. The content of rotenone and deguelin in three biopesticides containing derris extract were analyzed by the developed method, the results showed 0.001-0.236 and

• Korean Journal of Environmental Agriculture
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• v.34 no.1
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• pp.1-5
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• 2015

BACKGROUND: The stabilities of the two alkaloidal insecticides of S. flavescens including matrine and oxymatrine are important factor to establish expiry date and usage manual for crop protection. However, the environmental stability of the compounds had not been studied with the extract and its commercial biopesticide. METHODS AND RESULTS: The environmental stabilities of the two alkaloids were performed with extract of S. flavescens, and its two commercial biopesticides both in controlled aquatic and soil conditions. The half-lives of the total matrines for the extract and its two commercial biopesticides were estimated over 200 days both under aerobic and anaerobic water condition. Under dry soil condition, the initial decay rates of the matrines were calculated 0.0804-0.1275 ($t_{1/2}$ 5.4-8.6 days), and the half-lives under wet soil condition were calculated 33.0-231 days. Total soil bacteria on the wet soil ranged 6.0-8.0 log CFU/g-soil during the experiments period. CONCLUSION: The aquatic mixture of the extract showed excellent stability both with the extract and its biopesticides, however, the stability of soil mixture were shorter than the aquatic mixture, suggesting that soil metal consider as a catalyst for the degradation of the two alkaloids.