• Korean Journal of Weed Science
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• v.16 no.2
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• pp.132-139
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• 1996

Acetolactate synthase(ALS) activity was determined in germinating seedlings of two rice cultivars treated with cinosulfuron [3-(4,6-dimethoxy-1,3,5-triazin-2-yl)-1-[2-methoxyethoxy)-phenylsulfonyl]-urea]. IR 74(Indica type) was more tolerant than Hwajinbyeo(Japonica type) under various rates of cinosulfuron applied at the pregermination stage. In vitro response of ALS activity in the two rice cultivars was similar to $I_{50}$ values(cinosulfuron concentration required for 50% inhibition of ALS activity) of about 23ppb. In vivo, ALS activity of IR 74 increased as the seedlings grew, but that of Hwajinbyeo dropped at 5 days after 10ppm cinosulfuron treatment and shoot growth of Hwajinbyeo lagged at 4 to 5 days after herbicide treatment. ALS activity and shoot growth of Hwajinbyeo was resumed from cinosulfuron-induced inhibition at 6 days after cinosulfuron treatment. The differential response of ALS activity in two different rice cultivars against cinosulfuron may not be due to difference of ALS sensitivity, but rather due to different metabolic inactivation rates of cinosulfuron.

• BMB Reports
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• v.33 no.3
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• pp.195-201
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• 2000

A human gene has been reported that may encode the enzyme acetohydroxyacid synthase. Previously this enzyme was thought to be absent from animals although it is present in plants and many microorganisms. In plants, this enzyme is the target of a number of commercial herbicides and the use of these compounds may need to be reassessed if the human enzyme exists and proves to be susceptible to inhibition. Here we report the construction of several plasmid vectors containing the cDNA sequence for this protein, and their expression in Escherichia coli. High levels of expression were observed, but most of the protein proved to be insoluble. The small amounts of soluble protein contained little or no acetohydroxyacid synthase activity. Attempts to refold the insoluble protein were successful insofar as the protein became soluble. However, the refolded protein did not gain any acetohydroxyacid synthase activity. In vivo complementation tests of an E. coli mutant produced no evidence that the protein is active. Incorrect folding, or the lack of another subunit, may explain the data but we favor the interpretation that this gene does not encode an acetohydroxyacid synthase.

• Korean Journal of Weed Science
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• v.30 no.3
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• pp.199-205
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• 2010

This study was conducted to investigate the phytotoxic effects of 19 essential oils on seed germination and initial growth of rapeseed (Brassica napus L.). We found that anise, cinnamon, citronella, clove, geranium, lemongrass, mustard and pine oils completely inhibited germination of rapeseed at $100{\times}$ dilute solution. Based on the inhibition rates of rapeseed emergence and initial growth, three essential oils (cinnamon, clove, and geranium) were selected as potential bio-herbicides. Under pre-emergence applications of cinnamon, clove, and geranium oils at 90 kg ai $ha^{-1}$, rates of rapeseed emergence were 7.1, 25.0, and 3.6% and its initial growth were 22.0, 9.9 and 11.0%, respectively.

• Analytical Science and Technology
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• v.22 no.3
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• pp.228-234
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• 2009

To gain further insight into herbicide detoxification of plant, we purified a glutathione S-transferase from Brassica oleracea (BoGST) and studied its substrate specificity towards several xenobiotic compounds. The BoGST was purified to electrophoretic homogeneity with approximately 10% activity yield by DEAE-Sephacel and GSHSepharose column chromatography. The molecular weight of the BoGST was determined to be approximately 23,000 by SDS-polyacrylamide gel electrophoresis and 48,000 by gel chromatography, indicating a homodimeric structure. The activity of the BoGST was significantly inhibited by S-hexyl-GSH and S-(2,4-dinitrophenyl)GSH. The substrate specificity of the BoGST displayed high activities towards CDNB, a general GST substrate and ethacrynic acid. It also exhibited GSH peroxidase activity toward cumene hydroperoxide.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.122-131
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• 1996

The inhibition characteristics of chlorsulfuron [CHL, 2-chloro-N-[{ (4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino}carbonyl]benzenesulfonamide] and imazaquin [IMA, 2-{4,5-dihydro-4-methyl-4-(1-methy-lethyl)-5-oxo-1H-imidazol-2-yl}-3-quinolinecarboxylic acid] on acetolactate synthase(ALS) activity of corn plants were investigated. CHL and IMA rapidly inhibited ALS activity of corn plants in vitro. Their $I_{50}$ values for ALS activity were 100nM and $5{\mu}M$, respectively, indicating that CHL had 50 times more inhibitory effect on ALS activity than IMA. The first applied herbicide had a dominant inhibitory effect on ALS activity when the two herbicides were applied sequentially. Branched-chain amino acids, valine(Val), leucine(Leu), and isoleucine(Ile) showed a feedback inhibition on ALS activity ; Val or Leu had a more inhibitory effect on ALS activity than Ile. Branchedchain amino acids and CHL or IMA exhibited an additive effect on inhibiting ALS activity. This suggests that branched-chain amino acids inhibit ALS activity by a different mechanisms) from that of CHL or IMA. Apparent ALS activity, which was measured on the basis of the conversion of pyruvate to acetolactate, was decreased by the addition of 2-ketobutyrate into the ALS reaction mixture in a concentration-dependent manner. In addition, kinetic studies revealed that CHL acts as a noncompetitive inhibitor, while IMA acts as an uncompetitive inhibitor to ALS with respect to pyruvate.

• Korean Journal of Weed Science
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• v.15 no.3
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• pp.232-237
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• 1995

Effect of azimsulfuron {1-(4,6-dimethoxypyrimidin-2-yl)-3-[1-methyl-4-(2-methyl-2H-tetrazol-5-yl) pyrazol-5-ylsulfonl]urea} combined with eight annual herbicides on shoot and root growth of rice (Oryza sativa L.) and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] was investigated. Annual herbicides used were four thiocarbamates (dimepiperate, molinate, esprocarb, and thiobencarb), two acetanilides (butachlor and pretilachlor), one urea (dymron), and one oxadiazole (oxadiazon) herbicide. Growth inhibition in rice shoot was greater with azimsulfuron mixed with the annual herbicides than with azimsulfuron only. The azimsulfuron mixtures did not bring about decrease in growth inhibition of rice shoot. However, safening effect in root growth of rice was obtained when dimepiperate, molinate and dymron were combined with greater than 10ppm of azimsulfuron. Greater inhibition in shoot and root growth of rice occurred with straight chain hydrocarbon substitute such as esprocarb and thiobencarb than with cyclohydrocarbon substitute such as dimepiperate and molinate. Application of the azimsulfuron mixtures resulted in increase. in growth inhibition of shoot and root growth of barnyardgrass as compared with when azimsulfuron only was applied.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.268-275
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• 2006

ALA (5-aminolevulinic acid) has been proposed as a tetrapyrrole-dependent photodynamic herbicide by the action of the protoporphyrinogen IX oxidase (Protox IX). A study was conducted to determine photodynamic herbicidal effect of ALA on seedling growth of rice (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli Beauv. var. oryzicola Ohwi) under dry and wet conditions. ALA effect on early plant growth of rice and barnyardgrass was greatly concentration dependant, suggesting that it promotes plant growth at very low concentration and inhibits at high concentration. No significant difference in herbicidal activity of biologically and synthetically produced ALAs on plant lengths of test plants was observed ALA exhibited significant photodynamic activity regardless of PSDIP and its duration. Significant shoot growth inhibition by ALA soaking treatment exhibited apparently, indicating that ALA absorbed through root system was translocated into shoot part of plants. ALA reduced plant heights of rice and barnyardgrass seedlings by 6% and 27%, respectively, showing more tolerant to ALA in rice under wet condition. Leaf thickness was reduced markedly by ALA with increasing of ALA concentration, due to mainly membrane destruction and severe loss of turgidity in mesophyll cells, although the epidermal was little affected. It was observed that photodynamic herbicidal activity of ALA applied by pre-and post-emergence application exhibited differently on plant species, and that the activity of ALA against susceptible plants was highly correlated with growing condition.

• Korean Journal of Agricultural Science
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• v.48 no.2
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• pp.343-351
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• 2021

Screening was conducted using 200 kinds of plant extracts to explore herbicide-activated components of plant origin. We separated and purified active substances and elucidated chemical structures using Ligularia stenocephala M., which has strong activity and has not yet been studied. When the solvent fractions of the leaves of Ligularia stenocephala M. were tested for their herbicidal activity, ethyl acetate and chloroform layer showed an inhibition rate of 95.2% and 94.1%, respectively. In particular, the chloroform layer exerted more than 50% herbicidal activity at 10 ppm. From the chloroform layer with the highest herbicidal activity, we isolated three herbicidal active compounds using stepwise chromatography, specifically silica gel or octadecyl silica (ODS) column chromatography, Sep-pak cartridges, and high performance liquid chromatography (HPLC). Based on the analysis of the active compounds using electron ionization mass spectroscopy (EI-MS), ¹H-NMR, and ¹³C-NMR, we identified the active compounds as euparin, 5,6-dimethoxy-2-isopropenylbenzofuran, and liguhodgsonal. When the herbicidal activity of the identified compounds was tested, euparin showed selective herbicidal activity for lettuce at 10^-3 M, and both liguhogsonal and 5,6-dimethoxy-2-isoprophenylbenzofuran exerted selective activity for rice and Echinochloa crus-galli.

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.57-62
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• 2006

Several methods for determining the response of corn to glyphosate were investigated to provide a fast and reliable method for identifying glyphosate-resistant corn in vivo. Two bioassays were developed. One assay is named 'whole plant / leaf growth assay', in which the herbicide glyphosate is applied on the upper part of 3rd leaf and the growth of herbicide-untreated 4th leaf is measured at 3 day after treatment. in this assay, the leaf growth of conventional corn was inhibited in a dose dependent from 50 to $1600{\mu}g/mL$ of glyphosate and growth inhibition at $1600{\mu}g/mL$ was 55% of untreated control. The assay has the potential to be used especially in the case that the primary cause of glyphosate resistance is related with a reduction of the herbicide translocation. Another assay is named 'leaf segment / shikimate accumulation assay', in which the four excised leaf segments ($4{\times}4mm$) are placed in each well of a 48-well microtiter plate containing $200{\mu}L$ test solution and the amount of shikimate is determined after incubation for 24 h in continuous light at $25^{\circ}C$. In this assay, 0.33% sucrose added to basic test solution enhanced a shikimate accumulation by 3 to 4 times and the shikimate accumulation was linearly occurred from 2 to $8{\mu}g/mL$ of glyphosate, showing an improved response to the method described by Shaner et al. (2005). The leaf segment / shikimate accumulation assay is simple and robust and has the potential to be used as a high throughput assay in the case that the primary cause of glyphosate resistance is related with EPSPS, target site of the herbicide. Taken together, these two assays would be highly useful to initially select the lines obtained after transformation, to investigate the migration of glyphosate-resistant gene into other weeds and to detect a weedy glyphosate-resistant corn in field.

• Korean Journal of Agricultural Science
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• v.41 no.2
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• pp.85-99
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• 2014

Sulfonylurea (SU)-resistant weeds of eight annual weeds, Monochoria vaginalis, Scirpus juncoides and Cyperus difformis, etc., and four perennial weeds, Scirpus planiculmis, Sagittaria pigmaea, Eleocharis acicularis and Sagittaria trifolia as of 2013 since identification Monochoria korsakowii in the reclaimed rice field in 1998. And the resistant Echinochloa oryzoides to ACCase and ALS inhibitors has been confirmed in rice fields of the southern province, Korea in 2009. In the beginning, the M. vaginalis, S. juncoides and C. difformis of these SU-resistant weeds were rapidly and individually spreaded in different fields, however, these resistant weeds have been occurring simultaneously in the same filed recently. The resistant biotype by weed species demonstrated about 10-to 1,000-fold resistance, based on $GR_{50}$ values of the SU herbicides tested. And the resistant biotype of E. oryzoides to cyhalofop-butyl, pyriminobac-methyl, and penoxsulam was about 14, 8, and 11 times more resistant than the susceptible biotype base on $GR_{50}$ values. The products and applied area of SU-included herbicides have been increased rapidly, and have accounted for about 69% and 96% in Korea, respectively. In Korea, the main cause of SU-resistant weed is extensive use of these herbicides. The top ten herbicides by applied area were composed of all SU-included herbicides by 2003. The concentrated and successive treatment of ACCase and ALS inhibitors for control of barnyardgrass in rice led up to the resistance of E. oryzoides. Also, SU-herbicides like pyrazosulfuron-ethyl and imazosulfuron which effective to barnyardgrass can be bound up with the resistance of E. oryzoides. The ALS activity isolated from the resistant biotype of M. korsakowii to SU-herbicides tested was less sensitive than that of susceptible biotype. The concentration of herbicide required for 50% inhibition of ALS activity ($I_{50}$) of the SU-resistant M. korsakowii was 14-to 76-fold higher as compared to the susceptible biotype. No differences were observed in the rates of [$^{14}C$]bensulfuron uptake and translocation. Acetolactate synthase (ALS) genes from M. vaginalis resistant and susceptible biotypes against SU-herbicides revealed a single amino acid substitution of proline (CCT), at 197th position based on the M. korsakowii ALS sequence numbering, to serin (TCT) in conserved domain A of the gene. Carfentrazone-ethyl and pyrazolate were used mainly to control SU-resistant M. vaginalis by 2006 in Korea. However, the alternative herbicides such as benzobicyclone, to be possible to control simultaneously the several resistant weeds, have been developing and using broadly, because the several resistant weeds have been occurring simultaneously in the same fieled. The top ten herbicides by applied area in Korea have been occupied by products of 3-way mixture type including herbicides with alternative mode of action for the herbicide resistant weeds. Mefenacet, fentrazamide and cafenstrole had excellent controlling effects on the ACCase and ALS inhibitors resistant when they were applied within 2nd leaf stage.