• The Korean Journal of Pesticide Science
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• v.20 no.3
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• pp.189-196
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• 2016

Several microorganisms in particular Bacillus subtilis group have been isolated from diverse places such as soils and the gastrointestinal tract of ruminants etc., and used as biocontrol agent against various plant pathogens and utilized as plant growth promoting agents. Among them, Bacillus is well known as one of the most useful bacteria for biocontrol and plant growth promotion. Bacterium GH1-13 was isolated from a reclaimed paddy field in Wando Island and identified as Bacillus velezensis using phylogenetic analysis on the basis of 16S rRNA and gyrB gene. It was confirmed that GH1-13 produced indole acetic acid (IAA) associated with promoted growth of rice root. GH1-13 showed characteristics of antagonization against the main pathogen of rice as well as diverse pathogenic fungi. GH1-13 had biosynthetic genes, bacillomycin, bacilycin, fengycin, iturin, and surfactin which are considered to be associated closely with inhibition of growth of pathogenic fungi and bacteria. This study showed that GH1-13 could be used as a multifunctional agent for biocontrol and growth promotion of crop.

• The Korean Journal of Pesticide Science
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• v.10 no.1
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• pp.56-65
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• 2006

An antagonistic bacterial isolate, that inhibits the growth of plant pathogens, was selected and identified from 5,000 isolates screened from the rhizosphere of various crop plants. An isolate Bacillus sp. N32, tested against Colletotrichum gloeosporioides causing anthracnose disease in hot pepper, produced both a heat resistant antifungal protein and a heat sensitive antifungal protein. The heat resistant protein was partially purified by Ammonium sulfate fractionation and gel filtration chromatography. The bioautography showed that the proteins possessed high antifungal activity. The biosynthetic gene cluster responsible for the heat resistant antifungal protein was cloned from cosmid library using DNA probe obtained from PCR product with the primers targeting the conserved nucleotide sequence of the synthetic genes reported earlier, Most of the clones obtained showed higher homology to fengycin antibiotic synthetic gene family reported earlier. On the other hand, the heat sensitive protein was isolated from SDS-PAGE and electroblotting to determine the N-terminal amino acid sequences. The heat sensitive antifungal protein gene was cloned from the ${\lambda}-ZAP$ libraries using a DNA probe based on the N-terminal amino acid sequences of the heat sensitive protein. We are contemplating to clone and sequence the whole gene cluster encoding the heat sensitive protein for further analysis.

• The Korean Journal of Pesticide Science
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• v.10 no.1
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• pp.7-14
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• 2006

Three-dimensional quantitative structure-activity relationships (3D-QSARs) on the herbicidal activities against in-vitro pre-emergence rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) by new 5-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one derivatives were studied quantitatively using comparative molecular similarity indices analysis (CoMSIA) methodology. The optimized CoMSIA model(A5: $r^2_{cv.}=0.569$ & $r^2_{ncv.}=0.941$) for rice plant exhibited a good correlation with steric (31.6%) and hydrophobic (39.7%) factors of the substrate molecules, and the model (B4: $r^2_{cv.}=0.569$ & $r^2_{ncv.}=0.941$) for barnyardgrass exhibited a good correlation with electrostatic (46.7%) and H-bond acceptor field (30.8%), respectively. The predicted $R_1=SF_5,\;R_2=R_3=R_4=H(P1)$ substituent (Rice plant: $pI_{50}=4.84$ & Barnyardgrass: $pI_{50}=7.21$, ${\Delta}pI_{50}=2.37$) by the model (B4) not only exhibited to the highest herbicidal activity against barnyardgrass, but also exhibited to the highest selecticity between two plants.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.241-248
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• 2009

Pre-Harvest Residue Limit (PHRL) of bifenthrin during cultivation of grape was established by utilizing the dissipation curve and biological half-life of bifenthrin calculated from the analysis of 0, 1, 2, 3, 5, 7, 10, 15 days after treatment of bifenthrin. Grape sample was extracted and partitioned with acetonitrile and dichloromethane, respectively, and bifenthrin was determined with GC/ECD. Limit of quantitation (LOQ) of bifenthrin was 0.01 ng. Recoveries at two fortification levels of 0.1 and $0.5\;mg\;kg^{-1}$ were $104.08\;{\pm}\;1.24$ and $92.25\;{\pm}\;3.13%$, respectively. The biological half-lives of bifenthrin were about 21 days at standard application rate, while, 23 days at double application rate. Dissipation of bifenthrin on grape was not influenced by growth dilution effect. The PHRLs of bifenthrin were recommended as 0.60 and $0.55\;mg\;kg^{-1}$ for 10 and 5 days before harvest, respectively.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.223-231
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• 2009

This study was performed to develop a precise single residue analytical method of fungicide fenhexamid in representative crops for general residue analytical method which could be applied to most of crops. Korean cabbage, mandarin, apple and green pepper were selected, macerated, extracted with acetone, concentrated and partitioned with dichloromethane. Then the extracts were concentrated and cleaned-up through Florisil column with ethyl acetate/0.1% acetic acid in hexane [15:85, (v/v)] before concentration and analysis with HPLC. LOQ (Limit of Quantitation) of fenhexamid was 1 ng (S/N>10) and MQL (Method Quantitative Limit) was 0.01 mg/kg. Recoveries were measured at two fortification levels (10 MQL and 50 MQL) on crop samples and ranged from 85.2% to 94.8% (mean recoveries) and coefficients of variation were <10% regardless of sample type.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.290-297
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• 2009

This research aims to contribute the characterization of acetolactate synthase (Ec 4.1.3.18; ALS) and the resistance mechanism by sequence analysis of ALS gene of the sulfonylurea-resistant and -susceptible Monochoria vaginalis. The ALS gene was obtained from susceptible (S) and resistant (R) M. vaginalis to sulfonylurea herbicides (SUs). The 815 bp the fragment and the genomic DNA sequence coding for acetolactate synthase (ALS) of S and R biotypes of M. vaginalis were cloned and sequenced. Nineteen clones were divided greatly into 4 groups as result of sequencing. The first group was not difference to S type, the second group was amino acid of P197S which found point mutations causing substitution of serine for proline at amino acid 197, the third group was observed greatly other part of 6 places than group 1, and the fourth group appeared the intergrade of group 1 and 3. Therefore, it could be assumed what ALS gene of various types can be one plant. The peptide of the 13 amino acid Domain A region for ALS genes from R biotype of M. vaginalis differed from that of the S biotype by one base substitution at proline codon of Domain A. It could also be confirmed that point mutation of serine for proline at amino acid 197.

• The Korean Journal of Pesticide Science
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• v.12 no.1
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• pp.18-23
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• 2008

3D-QSAR on the inhibitory activities of 6-bromobenzo-[4,5]imidazo[$1,2{\alpha}$]-pyridin-8,9-diones analogues as substrate molecule were studied quantitatively using CoMFA and CoMSIA methods. The statistical values of CoMFA model was better predictability and fitness than CoMSIA model. The inhibitory activities according to the optimized CoMFA 2 model were dependent on the steric field (90.4%). From the CoMFA contour maps, it is found that the branched side chain as R-group will be directly attached to the carbon atom (ipso carbon) of substituent, the inhibitory activities had expected to increase. The positive charge favor groups were placed in the position between imidazol ring and pyridine ring, the inhibitory activities would increase. And if the groups of liner type will be substituted, hydrophilic favor group would raise inhibitory activities.

• The Korean Journal of Pesticide Science
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• v.21 no.1
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• pp.1-8
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• 2017

Although a global ban on the use of endosulfan, an organochloline insecticide, has taken effect in mid-2012, it has been still used in several countries, including India and China, and detected in diverse environments in the world due to its relative persistence and semi-volatility. In this study, the effect of endosulfan on soil bacterial community was investigated using 16S rRNA gene pyrosequencing method. When endosulfan was applied to an upland soil at a rate of 100 mg/kg soil (ES soil), the number of operational taxonomic units (OTU) and diversity indices for bacteria initially decreased and gradually recovered to the level of the non-treated soil (NT soil) during an eight-week incubation period. At bacterial phylum level, relative abundances of Proteobacteria and Verrucomicrobia were higher while those of Chloroflexi and Spirochaetes were lower in the ES soil than in the NT soil, suggesting that an endosulfan application affects the bacterial community structure in soil. In the ES soil, the relative abundances of the OTUs affiliated to the genera Sphingomonas and Burkholderia increased in the initial period of incubation while those affiliated to the genera Pseudonocardia and Opitutus increased in the late period of incubation. Because the first three genera contain bacterial strains reported to degrade endosulfan, they are expected to be involved in the degradation of endosulfan, probably one after another.

• The Korean Journal of Pesticide Science
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• v.9 no.2
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• pp.140-145
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• 2005

Quantitative Structure Activity Relationship (QSAR) assumes the relatedness between physical property and biological activity. However, activity data measured at single concentration such as percent activity have not been used extensively for modeling purpose. This probably comes from the fact that these values are qualitative instead of quantitative. To utilize percent activity data for molecular modeling, we classified the whole data into two classes. One class represents the active while the other signifies the inactive. The percent activity data of ${\beta}$-Ketoacetoanilides measured for TLB (Tomato Late Blight) were investigated. CoMFA (Comparative Molecular Field Analysis) was used as a discriminant function. Using CoMFA provides 3D (three dimensional) information, which is crucial for chemical insight. It can also serve as a predictive model. The resultant model classified the given data correctly (98%). When LOO (leave-one-out) crossvalidation procedure was applied, the classification accuracy was 69%. Therefore two class approximation of percent activity data with CoMFA can be utilized to understand the relationship between chemical structure and biological activity and design subsequent chemical analogs.

• The Korean Journal of Pesticide Science
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• v.9 no.2
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• pp.159-165
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• 2005

A sensitive derivatization method by using the TFE/TFAA as derivative reagent is proposed for the determination of acidic herbicides in water, by using this method, method detection limits are improved by 10 times and sample volumes are decreased by 5 times compared with other methods such as U.S. EPA and SPEED 98. And also, in order to suggest higher creditable standard operating procedure (SOP), intra- and inter-lab validation test carried out by four laboratories include our lab. The results of intra and inter-lab validations in same experimental conditions show good linearity in given range of concentrations as a $0.1{\sim}10.0$ ng/ml, and range of accuracies and precisions show $-20.5{\sim}12.2$ bias%, $0.55{\sim}24.48%$ (for intra-lab validation) and $-6.66{\sim}0.80 bias%$, $1.92{\sim}13.86%$ (for inter-lab validation), respectively.