• Weed & Turfgrass Science
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• v.3 no.3
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• pp.165-173
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• 2014

This review study was conducted to recommend the effective use of herbicide mixtures in Korea. The herbicide ingredients by Herbicide Resistancce Action Committee (HRAC) was classified into 23 groupes according to the mode of action (acetyl CoA carboxylase inhibitors, acetolactate synthase, photosystem I and II inhibitors, protoporphyrinogen oxidase inhibitors, carotenoid biosynthesis inhibitors, enolpyruvyl shikimate-3-phosphate synthase inhibitors, glutamine synthetase inhibitors, dihydropteroate synthetase inhibitors, mitosis inhibitors, cellulose inhibitors, oxidative phosphorylation uncouplers, fatty acid and lipid biosynthesis inhibitors, synthetic auxins, auxin transport inhibitors and potential nucleic acid inhibitors or non-descript mode of action). The rice herbicide mixtures registered in Korea were classified based on the guideline of HRAC. Accordingly, such a classification system for resistance management can help to avoid continuous use of the herbicide having the same mode of action in the same field.

• Bulletin of the Korean Chemical Society
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• v.27 no.4
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• pp.549-555
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• 2006

Acetohydroxyacid synthase (AHAS, EC 2.2.1.6 also referred to as acetolactate synthase) catalyzes the first common step in the metabolic pathway leading to biosynthesis of the branched-chain amino acids in plants and microorganisms. Due to its presence in plants, AHAS is a target for the herbicides (sulfonylurea and imidazolinone), which act as potent inhibitors of the enzyme. Recently, we have shown [J. Kim, D.G. Baek, Y.T. Kim, J.D. Choi, M.Y. Yoon, Biochem. J. (2004) 384, 59-68] that the residues in the “mobile loop” 567-582 on the C-termini are involved in the binding/stabilization of the active dimer and ThDP (thiamin diphosphate) binding. In this study, we have demonstrated the role of the W573 in the mobile loop of the C-termini of tobacco AHAS. The substitution of this W573 residue caused significant perturbations in the activation process and in the binding site of ThDP. Position W573 plays a structurally important role in the binding of FAD, maintaining the enzyme active site in the required geometry for catalysis to occur. In here we propose that the tryptophan at position 573 is important for the catalytic process.

• Weed & Turfgrass Science
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• v.6 no.4
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• pp.345-349
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• 2017

Herbicides are important weed control tools for increasing crop yields and the efficiency of crop production. As the use of herbicides increases, the occurrrence of herbicide-resistant weeds has been an increaing problem. In Korea, since the first occurrence of acetolactate synthase (ALS) inhibitor resistant Monochoria korsakowii was reported in the Seosan reclaimed paddy field in 1998, resistance has been reported in 14 weed species, including Echinochola spp. and their populations are gradually increasing. The objective of this study is to investigate the nationwide occurrence of ALS and Acetyl-CoA Carboylase inhibitor resistant Echinochloa spp. in Korea. In 2013, 2014, and 2015, we collected 594 accessions of Echinochloa spp. in Korean rice fields except for Jeonnam and Chungbuk provinces. They were then treated with the recommended rates of penoxsulam and cyhalofop-butyl. We harvested seeds from 45 accessions of E. oryzicola in the case of cyhalofop-butyl treatment. Also, 44 and 46 accessions of E. oryzicola and E. crus-galli survived and their seeds were harvested after penoxsulam treatment. Twenty accessions of E. oryzicola survived from both herbicides inferring possible multiple resistance. Two accessions out of 20 inferred from possible multiple resistance survived after cyhalofop-butyl treatment at a dose of $500ga.i.ha^{-1}$. Seeds of herbicide resistant populations will be provided and utilized for further research.

• Korean Journal of Weed Science
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• v.17 no.3
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• pp.325-333
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• 1997

Selection of pepper (Capsicum sp.) cultivars tolerant to acetolactate synthase (ALS)-inhibiting herbicides {imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3=pyridine-carboxylic acid, and primisulfuron methyl 2-[[[[[4,6-bis(difluoromethoxy)-2-pyrimidinyl]amino] carbonyl]amino]sulfonyl]benzoate} was investigated. Pepper cultivars such as Red Top, Happy Dry, Golden Tower, and Hagyeorae showed relatively tolerant response to imazethapyr, while cultivars; Korea, Cheongyang, Oriental Glory, and Hanam were susceptible. Red Horn, Jopoong, Kwangbok, and Wangcho cultivars were tolerant to primisulfuron whereas Korea, Dahhong, Chamjoah, and Poongchon cultivars were susceptible. Determination of growth inhibition by ALS-inhibiting herbicides showed that the $I_{50}$ estimates of growth from the susceptible- and tolerant-cultivars were 0.075 and 0.20kg ai/ha for imazethapyr; 0.06 and 0.16kg ai/ha for primisulfuron, respectively. Furthermore, the $GR_{50}$ estimates of growth from the susceptible and tolerant cultivars were 0.05 and 0.20kg ai/ha for imazethapyr; 0.07 and 0.16kg ai/ha for primisulfuron, respectively. This result, based on the $GR_{50}$ and $I_{50}$ values, indicates that responses of pepper to ALS-inhibiting herbicides between tolerant- and susceptible-cultivars were different about 3- to 4-fold to imazethapyr, and 2- to 3-fold to primisulfuron.

• Korean Journal of Weed Science
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• v.17 no.2
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• pp.199-206
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• 1997

Chlorsulfuron, an acetolactate-synthase-inhibiting sulfonylurea herbicide, induces many metabolic and physiological changes in susceptible plants. The objective of this study was to determine to what extent chlorsulfuton-induced phytotoxicity was due to a shortage of final products(the branched-chain amino acids valine, leucine, and isoleucine) or to an accumulation of a toxic metabolite(2-ketobutyrate), or both, in a susceptible species. Chlorsulfuron-treated canola seedlings showed growth inhibition and injury symptoms that included chlorosis, downward leaf rolling, and accumulation of anthocyanins. Supplementation with valine, leucine, and isoleucine prevented the chlorsulfuron-induced growth inhibition and injury symptoms only partially, suggesting that factor(s) other than a shortage of the branched-chain amino acids also are involved in the phytotoxicity. Canola seedlings treated with 2-ketobutyrate showed reduced growth, but they showed different changes in metabolites than seedlings treated with chlorsulfuron. The results suggest that 2-ketobutyrate is not involved in chlorsulfuron-induced phytotoxicity. We conclude that chlorsulfuron-induced phytotoxicity is due at least in part to a shortage of branched-chain amino acids.

• The Korean Journal of Pesticide Science
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• v.8 no.4
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• pp.332-337
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• 2004

A suspected biotype of Scirpus planiculmis to be resistant to sulfonylurea(SU) herbicides was identified in Seosan reclaimed paddy fields in Korea, in 2004. The fields have been cultivated for monocultural rice production with wet-direct seeding method and continuously treated with SU-based herbicide mixtures for thirteen years since 1990. In greenhouse studies, 6 different SU herbicides, such as azimsulfuron, bensulfuron-methyl, cinosulfuron, ethoxysulfuron imazosulfuron and pyrazosulfuron-ethyl, completely controlled the Musan assession of Scirpus planiculmis at the recommended dose of each herbicide, however, the Seosan accession of S. planiculmis biotype was survived 20 to 45% even treated with 5 times higher dose of each recommended rate of all herbicides treated. The $GR_{50}$ values of 6 SU herbicides for Seosan accession of S. planiculmis were 47 to 100 times higher than those for Musan accession of S. planiculmis. The $I_{50}$ values pyrazosulfuron-ethyl to acetolactate synthase(ALS) extracted from Sesan and Muan accession of S. planiculmis were 409 nM and 0.8 nM, respectively. The $I_{50}$ value of Seosan was 511 times higher than that of Muan accession. These results suggested that the Seosan accession of S. planiculmis have strong resistant characteristics to 6 SU herbicides, respectively, indicating that resistance might be due to the alteration in the target site of ALS.

• Korean Journal of Weed Science
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• v.16 no.4
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• pp.317-326
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• 1996

To know whether pyrazosulfuron-ethyl(PYR) and imazaquin(IMA), known as a acetolactate synthase(ALS) inhibitors, have a same herbicidal action pattern in rice(Oryza sativa) or barnyardgrass (Echinochloa crus-galli), an inhibition pattern and a response characteristics in combination with dymron or butachlor were investigated. In contrast to the phytotoxicity of rice treated with IMA, the one treated with PYR was completely tended to be recovered after 25 days after treatment. Safening effect of dymron against PYR was effectively developed to transplanted-rice, while such an effect was not shown in combination with IMA. In combination with PYR and butachlor, antagonistic effect was observed in both simultaneous or sequential treatment on bamyardgrass, however, additive effect was rather shown in combination with IMA and its activity was dominantly dependent on the first applied compound. $I_{50}$ of PYR and IMA on the ALS extracted from barnyardgrass was $4{\times}10^{-7}$M and $2.8{\times}10^{-6})$M, respectively. Butachlor did not affect their activities on ALS in vitro. These results suggest that PYR and IMA might have a different action each other in the pathway to a final herbicidal activity even though their primary action site is ALS.

• Korean Journal of Weed Science
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• v.14 no.1
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• pp.8-15
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• 1994

The mode of safening action and potency of the 1, 8-naphthalic anhydride(NA) were investigated in corn(Zea mays) and soybean(Glycine max) treated with herbicide bensulfuron[2-{{{{{(4,6-dimethoxy-2-pyrimidinyl)amino}carbonyl}amino}sulfonyl}methyl}benzoic acid] and imazaquin[2-{4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl} 3-quinolinonecarboxylic acid]. Seed dressing with 0.2%(w/w) NA showed successful protection in corn against injury from herbicide bensulfuron and imazaquin but not in soybean. Safening factors of NA against bensulfuron and imazaquin were 10.2 and 5.0, respectively, in corn, while they were both 1.3 in soybean. In vivo, Glutathione-S-transferase(GST) activity of NA-treated corn and soybean increased 1.8-and 1.3-fold, respectively, but the activity was not affected by the herbicides in vitro. Acetolactate synthase(ALS) levels of NA-treated corn was increased 1.3-fold, but not changed in soybean. Tolerance of ALS activity to the herbicides was slightly greater in ALS obtained from NA-treated corn than that from the untreated, whereas the difference was not found in soybean. A significant increase of ACCase due to NA occurred in corn, but not in soybean. The herbicides did not affect in vitro ACCase activity.

• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.58-62
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• 2001

New benzenesulfonylurea derivatives possessing ${\beta}$-hydroxyalkyl subgroup were synthesized and found to have interesting herbicidal activity in greenhouse screening.

• The Korean Journal of Pesticide Science
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• v.6 no.1
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• pp.45-48
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• 2002

New benzenesulfonylurea derivatives possessing bicyclic ketal subgroup were synthesized and shown to have interesting herbicidal activities under upland greenhouse screening.