• The Korean Journal of Pesticide Science
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• v.4 no.2
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• pp.21-28
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• 2000

A new fourty six 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)-N-phenylpro- pionamide derivatives were synthesized and the herbicidal activities against rice plant and barnyard grass with pre-emergence in down land were measured. The structure activity relationships (SAR) between the activities and physicochemical parameters of the substituted(X) N-phenyl group in substrates were analyzed and discussed by Free- Wilson and Hansch method from the basis on the former study (Sung. et. al., 1999). The conditions of selective herbicide activity both the barnyard grass and rice plant are shown that the optimal hydrophobicity, $({\pi})_{opt.}=1.34$ and electron donating with field effect (F<0) of meta and ortho, para-substituted mono or disubstituent on the N-phenyl ring were found to contribute significantly. The herbicidal activities against barnyard grass are roughly the same as the results in up land whereas damage to rice plant in down land more increase than that of up land. Degradation products in water are 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)propionic acid ((A)) (obs. pKa=4.35 & obs. logP=4.77) and 6-chloro-2-benzoxazolone (B) (obs. pKa=8.40 & obs. logP=2.90). These results were supposing that the hydrolysis product of substrates, (A) is comparatively absorbed in rice plant but not in barnyard grass. And it is assumed from the SAR equations that the 2,6-dimethyl-4-methoxymethyl group substituent ($pI_{50}=5.41$, 3g/ha) is selected as the most highest herbicidal activity against barnyard grass in green house.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.28-35
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• 1996

Tetrapion(2,2,3,3-tetrafluoropropionate sodium) has commonly been used for reed(Phragmites communis Trin.) control in uncultivated areas, especially in Japan. As an attempt to establish the screening system for selective herbicide controlling reed, tetrapion was tested as a standard herbicide to various weeds and crops including rice in a greenhouse. Symptoms of yellowing, twisting, stunting, and necrosis were observed in the herbicide-treated plants. The herbicide caused a severe damage on all crops examined, except cotton. Both direct seeded and transplanted rice were also sensitive to the herbicide. Its herbicidal activity was generally higher on grass weeds than on broadleaf weeds. It had a higher herbicidal activity with preemergence treatment than with postemergence treatment. In addition, field and greenhouse experiments were conducted to examine the effect of the herbicide on reed control. Its effect varied with the soil type of the treated field and the growth stage of reed. A relatively high dosage of the herbicide was required to control reed. It had an almost same effect on fairygrass(Miscanthus sinensis Anderss) as on reed. However, reed grown in a greenhouse was effectively controlled by the herbicide, having more effect with preemergence treatment than with postemergence treatment as observed in other plants treated with the herbicide. In conclusion, tetrapion has a great potential as a standard herbicide during the herbicide screening for selective reed control.

• The Korean Journal of Pesticide Science
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• v.7 no.2
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• pp.108-116
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• 2003

A series of new quinclorac family, herbicidal 3-phenyl-5-(3,7-dichloro-8-quinolinyl)-1,2,4-oxadiazole derivatives as substrate were synthesized and their growth inhibition activity $(pI_{50})$ against root and shoot of rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) were determined. And then comparative molecular field analysis (CoMFA) and molecular holographic quantitative structure- activity relationship (HQSAR) were compared in terms of their potential for predictiability. The statistical results were suggested that HQSAR based model had better predictability than CoMFA model. The selective factors to remove barnyard grass take electron withdrawing groups which can be created positive charge and steric bulky on the phenyl ring. Results revealed that the unknown 2,6-dichloro-substituent, U5 and 2,4,6-trichloro-substituent, U6(${\Delta}pI_{50}$=CoMFA: 1.18 & HQSAR: 1.82) were predicted as compound with higher activity and selectivity.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.183-192
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• 2002

Herbicidal effect of KSC-35089, a newly synthesized N-arylphthalimide compound, was examined, and its interaction with quizalofop-P-ethyl when foliar applied as a tank-mixture was evaluated under a greenhouse condition. KSC-35089 showed stronger herbicidal activity on broadleaves than grasses, suggesting that it would be an appropriate partner for non-selective weed control with quizalofop-P-ethyl, a strong grasskilling ageant. In general, the interaction between KSC-35089 and quizalofop-P-ethyl appeared to be additive, which indicates each compound acts on whole plant level independently. This additive interaction was confirmed in a spectrum test using 19 grasses and 26 broadleaves. Under the greenhouse condition, all tested plants were controlled around 90% level through a foliar application with a tank-mixture of KSC-35089 at 64 g ai/ha and quizalofop-P-ethyl at 32 g ai/ha. Further study would be required on the action mechanism of this additive interaction.

• Korean Journal of Weed Science
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• v.7 no.2
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• pp.220-235
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• 1987

The experiment was carried out to find the feasibility of using Oxyfluorfen in the paddy fields by investigating the difference of selective activity of Oxyfluorfen among rice cultivars and major paddy weed species. The dosage of Oxyfluorfen that show selective activity between rice cultivars and weed species ranged from 0.1 to 0.4kg ai/ha. The degree of growth inhibition was in order of whole-plant soaking application > root soaking application > stem bandage application, and in that case $10^{-5}$M Oxyfluorfen was treated after emergence. Especially the growth inhibition of rice cultivars and Cyperus serotinus was low, among others. Photosynthesis was severely inhibited at the Oxyfluorfen level above $10^{-4}$ M in all the tested weeds, but inhibition of respiration was not to be seen. Isolated single cells of two rice cultivars and Cyperus serotinus were tolerant to $10^{-5}$M Oxyfluorfen,but those of Echinochloa crus-galli and Sagittaria pygmaea were susceptible comparatively. The growth inhibition of suspension cultured rice cell induced by the increments of Oxyfluorfen concentration, and the degree of inhibition was higher in C.V. Mushakdanti than in C.V. Aichiasahi.

• Korean Journal of Weed Science
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• v.14 no.2
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• pp.107-111
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• 1994

Selective action of root-treated oxyfluorfen [(2-chloro-4-thrifluoromethylphenyl)-3'-ethoxy-4'-nitrophenyl ether] and chlomethoxynil [2, 4-dichlorophenyl-3'-methoxy-4'-nitrophenyl ether] were investigated. Oxyfluorfen showed greater activity to all plant species than chlomethoxynil. $^{14}C$-oxyfluorfen was little metabolized in roots of the plant species and more slowly absorbed than $^{14}C$-chlomethoxynil. These results suggest that herbicidal activity of oxyfluorfen at the site of action is higher than chlomethoxynil. In the tested plants, rice, barnyardgrass, sorghum, and corn were absorbed less of the oxyfluorfen and chlomethoxynil than the broad leaf plant species. However, no clear relationship was observed between a degree of tolerance and absorption and metabolism of both herbicides by the plant species.

• The Korean Journal of Pesticide Science
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• v.8 no.3
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• pp.151-161
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• 2004

Three dimensional quantitative structure-activity relationships (3D-QSAR) studies for the protox inhibition activities against root and shoot of rice plant (Orysa sativa L.) and barnyardgrass (Echinochloa crus-galli) by a series of new A=3,4,5,6-tetrahydrophthalimino, B=3-chloro-4,5,6,7-tetrahydro-2H-indazolyl and C=3,4-dimethylmaleimino group, and R-group substituted on the phenyl ring in 1-(5-methyl-3-phenylisoxazolin-5-yl)methoxy-2chloro-4-fluorobenzene derivatives were performed using comparative molecular field analyses (CoMFA) methodology with Gasteiger-Huckel charge. Four CoMFA models for the protox inhibition activities against root and shoot of the two plants were generated using 46 molecules as training set and the predictive ability of the each models was evaluated against a test set of 8 molecules. And the statistical results of these models with combination (SIH) of standard field, indicator field and H-bond field showed the best predictability of the protox inhibition activities based on the cross-validated value $r^2_{cv.}$ $(q^2=0.635\sim0.924)$, conventional coefficient $(r^2_{ncv.}=0.928\sim0.977)$ and PRESS value $(0.091\sim0.156)$, respectively. The activities exhibited a strong correlation with steric $(74.3\sim87.4%)$, electrostatic $(10.10\sim18.5%)$ and hydrophobic $(1.10\sim8.30%)$ factors of the molecules. The steric feature of molecule may be an important factor for the activities. We founded that an novel selective and higher protox inhibitors between the two plants may be designed by modification of X-subsitutents for barnyardgrass based upon the results obtained from CoMFA analyses.

• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.1-11
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• 2001

New technologies will have a large impact on the discovery of new herbicide site of action. Genomics, combinatorial chemistry, and bioinformatics help take advantage of serendipity through tile sequencing of huge numbers of genes or the synthesis of large numbers of chemical compounds. There are approximately $10^{30}\;to\;10^{50}$ possible molecules in molecular space of which only a fraction have been synthesized. Combining this potential with having access to 50,000 plant genes in the future elevates tile probability of discovering flew herbicidal site of actions. If 0.1, 1.0 or 10% of total genes in a typical plant are valid for herbicide target, a plant with 50,000 genes would provide about 50, 500, and 5,000 targets, respectively. However, only 11 herbicide targets have been identified and commercialized. The successful design of novel herbicides depends on careful consideration of a number of factors including target enzyme selections and validations, inhibitor designs, and the metabolic fates. Biochemical information can be used to identify enzymes which produce lethal phenotypes. The identification of a lethal target site is an important step to this approach. An examination of the characteristics of known targets provides of crucial insight as to the definition of a lethal target. Recently, antisense RNA suppression of an enzyme translation has been used to determine the genes required for toxicity and offers a strategy for identifying lethal target sites. After the identification of a lethal target, detailed knowledge such as the enzyme kinetics and the protein structure may be used to design potent inhibitors. Various types of inhibitors may be designed for a given enzyme. Strategies for the selection of new enzyme targets giving the desired physiological response upon partial inhibition include identification of chemical leads, lethal mutants and the use of antisense technology. Enzyme inhibitors having agrochemical utility can be categorized into six major groups: ground-state analogues, group specific reagents, affinity labels, suicide substrates, reaction intermediate analogues, and extraneous site inhibitors. In this review, examples of each category, and their advantages and disadvantages, will be discussed. The target identification and construction of a potent inhibitor, in itself, may not lead to develop an effective herbicide. The desired in vivo activity, uptake and translocation, and metabolism of the inhibitor should be studied in detail to assess the full potential of the target. Strategies for delivery of the compound to the target enzyme and avoidance of premature detoxification may include a proherbicidal approach, especially when inhibitors are highly charged or when selective detoxification or activation can be exploited. Utilization of differences in detoxification or activation between weeds and crops may lead to enhance selectivity. Without a full appreciation of each of these facets of herbicide design, the chances for success with the target or enzyme-driven approach are reduced.

• The Korean Journal of Pesticide Science
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• v.10 no.2
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• pp.76-83
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• 2006

In order to investigate the impacts of non-selective herbicide, glufosinate-ammonium (ammonium 4-[hydroxy(methyl)phosphinoyl] -DL-homoalaninate, GLA) to the non-target organisms, earthworm was exposed to GLA in the field soil for a month, and microbial populations in the soil were investigated after application of GLA. Simultaneously, the residues of GLA and its metabolite, 3-MPP were analyzed in the same soil. Meanwhile, to elucidate the influence of GLA to the growth of non-target crops incase of inter-furrow application, the amounts of carotenoid, chlorophyll, amino acid, proteins and sugars in the leaves of potato and chinese cabbage grown in the same field were investigated. In result, the dead earthworm was not observed during the test period, and the increasing rates of bodyweight were $9.410{\sim}11.603%$ in GLA-treated plots and 5.645% in GLA-untreated plots. The populations of fungi, bacteria and actinomycetes in the GLA-treated soils were $6.2{\times}10^4$, $1.5{\times}10^6$ and $5.7{\times}10^4$, respectively. They maintained relatively similar levels to the control which were $3.7{\times}10^4$, $3.7{\times}10^5$ and $3.7{\times}10^4$, respectively. In residue analysis, the limit of detection of GLA was 0.02 mg $kg^{-1}$, that of 3-MPP was the same level, and the half-life of GLA was 15 days in sandy clay loam soil. This result indicates that GLA was degraded very quickly in field soil. On the other hand, the amounts of physiological, biochemical components such as carotenoid, amino acid, chlorophyll, protein and sugar were ranged from 90.0 to 104.3% in potato and from 99.0 to 112.7% in chinese cabbage. Comparing with hand-weeded plots, it is indicated that GLA had not affected to the growth of non-target crops when applied at inter-furrow in crops-growing field.