• Korean Journal of Weed Science
• /
• v.18 no.4
• /
• pp.314-324
• /
• 1998

This study was carried out to investigate the herbicidal action characteristics of EK3143 and EK3150, newly synthesized cyclohexanedione analogues, and their inhibitory effects on the acetyl-CoA carboxylase activity isolated from various plants. Sethoxydim, a typical cyclohexanedione herbicide, had a high herbicidal activity against only grasses with growth inhibition, leaf chlorosis and necrosis. EK3143 and EK3150 had a lower effect against grasses but a higher effect against broadleaf plants such as black nightshade and velvetleaf than sethoxydim had. Low rate application of EK3143 induced leaf bleaching(whitening), while high rate application induced the same symptoms as those of sethoxydim. EK3150 induced more significant whitening, additionally accompanying a curling of meristem part in broadleaf plants. A consistant tendency was observed between the growth inhibition against grasses and the senstivity of grass ACCase to these compounds, but not between herbicidal activities against broadleaf plants and the senstivity of dicotyledonous ACCase; i.e. EK3150, which had higher herbicidal activity against black nightshade and velvetleaf than EK3143 had in greenhouse, rather showed lower ACCase inhibition. In EK3150-treated barnyardgrass, growth inhibition occurred prior to decrease of photosynthetic pigments, in contrast to that of norflurazon and EK3140. These results suggest that EK3143 and EK3150 may have two target sites, ACCase and an unknown site on fatty acid synthesis related to growth inhibition and bleaching respectively, and their symptoms would be appeared in different degree by a differential binding affinity between two action sites.

• Korean Journal of Weed Science
• /
• v.30 no.3
• /
• pp.291-299
• /
• 2010

Cyhalofop-butyl and penoxsulam, known for respective acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitor, have been widely using as a post-emergence foliar application for many years in wet-seeded rice field in Korea. Since 2009, control of Echinochloa oryzoides with cyhalofop-butyl and penoxsulam was no longer satisfactory. Greenhouse and experiment in rice field were conducted to confirm E. oryzoides resistance to ACCase and ALS inhibitors and to compare herbicide treatments for control of the resistant E. oryzoides to ACCase and ALS inhibitors. Three resistant E. oryzoides to ACCase and ALS inhibitors accessions were tested for levels of resistance to cyhalofop-butyl and penoxsulam, base on survival rate. Iksan and Kimje accessions were not any affected to the survival by treatment with recommended doses of two herbicides tested. Buan accession displayed an intermediate response of 62 and 72% survival at recommended doses of cyhalofop-butyl and penoxsulam, respectively. Survival rates to herbicides mixed with ACCase and ALS inhibitors at 3.5 leaf stage of E. oryzoides was over 80%. Benzobicyclon+fentrazamide+bensulfuron SC, benzobicyclon+mefenacet+bensulfuron SC, benzobicyclone +cafenstrole+pyrazosulfuron-ethyl GR controlled effectively by 2 leaf stage of resistant E. oryzoides to ACCase and ALS inhibitors. In the field experiment, single treatment of benzobicyclon+ fentrazamide+bensulfuron SC and benzobicyclon+mefenacet+bensulfuron SC failed to control E. oryzoides, but squential treatment of benzobicyclon+thiobencarb SE and benzobicyclon+ mefenacet+ bensulfuron SC controlled effectively it in rice infant seedling culture with machine. Our results suggest that resistant E. oryzoides to ACCase and ALS inhibitors had not developed multiple resistance to herbicides with different modes of action. In particular, cafenstrole, fentrazamide, mefenacet were effective control measures.

• Weed & Turfgrass Science
• /
• v.3 no.2
• /
• pp.110-113
• /
• 2014

The continuous use of acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors has led to the selection of herbicide resistant barnyardgrass populations in direct-seeded rice fields of Korea. This study was conducted to identify herbicide resistant barnyardgrass biotypes and to determine the cross- and multiple-resistance of them. 25% of the population collected from Taeahn was partially resistant to ACCase inhibitors and 22% collected from Kimjae were partially resistant to ALS inhibitors. However, 8.2% of the population from both sites was resistant to ALS and ACCase inhibitors. Resistance to sulfonylurea herbicide, flazasulfuron was identified from two barnyardgrass accessions collected from both Taeahn and Kimjae. One barnyardgrass accession from both sites was resistant to ACCase inhibitor, sethoxydim. The cross-resistance to ALS inhibitors was identified at one barnyardgrass accession from Taeahn and at two accessions from Kimjae. Further, crossresistance to ACCase inhibitors was also identified at barnyardgrass accessions from Taeahn and Kimjae. Multiple-resistance to flazasulfuron and sethoxydim was determined at four barnyardgrass accessions from Taeahn and at six accessions from Kimjae. Therefore, the herbicide mixture and sequences within a growing season or the herbicide rotation with different modes of actions across growing seasons are recommended to control herbicide-resistant barnyardgrass in infested fields.

• Korean Journal of Weed Science
• /
• v.31 no.2
• /
• pp.183-191
• /
• 2011

Weeding effect was investigated based on the leaf stages to several different herbicide treatments for an integrated weed management of herbicide resistant Echinochloa oryzoides to ACCase and ALS inhibitors in a rice field. Efficacy of soil-applied herbicide treatments before resistant E. oryzoides occurred was very effective. Pentaxazon 5% SC showed over 98% of weeding effect although E. oryzoides were emerged 31 days after the treatment. Until the leaf stage of 2.5, five herbicides, azimsulfuron carfenstole 1.05% GR, bensulfuron-methyl benzobicyclone mefenacet 24.52% SC, bensulfuron-methyl fentrazamide 7% SC, bensulfuron-methyl mefenacet oxadiargyl 21.6% SC and mefenacet pyrazosulfuron-ethyl 3.57% GR showed perfect weeding effect. Benzobicyclone mefenacet penoxulam 21.5% SC and mefenacet pyrazosulfuron-ethyl 3.57% GR were effective at the leaf stage of 3.0. It is very important to select the right herbicides for timing and their systematic application for controlling of E. oryzoides resistant to ACCase- and ALS-inhibitors.

• Weed & Turfgrass Science
• /
• v.6 no.1
• /
• pp.32-39
• /
• 2017

This study was carried out to investigate the ACCase inhibiting herbicide resistant Echinochloa oryzicola collected in a Honam rice field and to investigate the control of E. oryzicola in directly seeded paddy rice field. The study result showed that about 44% of the 67 biotypes collected in the rice field in Honam region were resistant to ACCase-inhibiting herbicides. The efficacy of several chemical herbicides on these resistant E. oryzicola biotypes was evaluated according to their application timings. Among herbicides applied 4 days before seeding, pretilachlor, butachlor, oxadiazon, oxadiargyl, oxadiazon+pretilachlor, and fentrazamide+oxadiargyl, provided 95% or higher control of the resistant E. oryzicola biotypes. Among the herbicides applied 10 days after seeding, bromobutide+fentrazamide+imazosulfuron, benzobicyclon+fentrazamide+imazosulfuron, pyrazosulfuron-ethyl+thiobencarb, fentrazamide+imazosulfuron, bromobutide+imazosulfuron+mefenacet and bromobutide+imazosulfuron+pyraclonil provided ${\geq}95%$ control of the weeds. Bromobutide+imazosulfuron+mefenacet and bromobutide+pyrazosulfuron-ethyl+pyriminobac-methyl, applied 15 days after seeding, provided ${\geq}95$ and 90% control of the weeds. Foliar application of cyhalofop-butyl+propanil at 30 days after seeding provided ${\geq}90%$ control of the weeds. In addition, oxaziclomefone provided ${\geq}90%$ control for 40 days after soil application. These results show that E. oryzicola biotypes resistant to ACCase-inhibiting herbicides could be effectively controlled in directly seeded rice in submerged paddy fields using single or tank-mixed chemical herbicides currently available on the market.

• The Korean Journal of Pesticide Science
• /
• v.14 no.3
• /
• pp.183-190
• /
• 2010

To search the new potent herbicidal agents by receptor-based approach, the interactions between receptor and substrate molecules from molecular docking to acetyl-CoA carboxylase(PDB code: 3K8X) of 2-(4-(6-chloro-2-benzoxazolyl)oxy)phenoxy-N-phenylpropionamide analogues (1-38) as substrate molecules were performed and discussed quantitatively. The most of the substrate molecules were formated 2 H-bonds between carbonyl oxygen atom of the substrate molecules and the amino acid residues (Ala1627 and Ile1735) in binding site of acetyl-CoA carboxylase (ACCase). But, the substrate molecules such as $R_l$=Acetyl substituents (6 & P9) were formated 3 H-bonds between H-bond acceptors in the substrate molecules and the H-bond donors in three amino acid residues including the rest residue (Gly 1998). Therefore, the inhibitory activity factors of the substrate molecules against ACCase are due to the H-bonding characters that will be able to apply to the optimization of herbicidal agents.

• Weed & Turfgrass Science
• /
• v.7 no.2
• /
• pp.166-169
• /
• 2018

Repeated use of ACCase inhibiting herbicides for a long time has resulted in increases of resistant Echinochloa oryzicola populations in paddy fields in middle west area of Korea. This study aims to investigate current status of herbicide resistant E. oryzicola in Gyeongsangnam-do, in which there is less information about herbicide resistance. For resistance frequency and dose-response study, seeds from 100 individual plants of E. oryzicola in Gyeongsangnam-do were collected and tested with cyhalofop-butyl. Seven percent of plants from Gyeongsangnam-do was resistant at a recommended rate of cyhalofop-butyl. $GR_{50}$ values (herbicide rates required to reduce plant growth 50%) for one representative resistant populations and five susceptible populations were $738g\;a.i.\;ha^{-1}$ and 66-234 (average 147)$g\;a.i.\;ha^{-1}$, respectively, indicating average 5 times difference in resistance. Although lower rate of frequency of herbicide resistance in Gyeongsangnam-do than in Jeollabuk-do, increases of herbicide resistance are expected in this area because of increases of direct seeded rice fields and increases of dependence on a specific herbicide. Therefore, it is necessary to monitor herbicide resistance regularly and conduct integrated herbicide resistance management in this area.

• Korean Journal of Weed Science
• /
• v.18 no.2
• /
• pp.161-170
• /
• 1998

Antagonistic mode of action of fenoxaprop-P-ethyl [ethyl(R)2-4-{(6-chloro-2-benzoxazolyloxy) phenoxy}propionate] with bentazon was investigated with respect to absorption, translocation, metabolism, and change in target site response of fenoxaprop-P-ethyl using four-leaf stage of rice(Oryza sativa L.) and barnyardgrass [Echinochloa eras-galli (L.) P. Beauv.]. Shoots of rice and barnyardgrass was more sensitive to fenoxaprop-P-ethyl than the roots. More than 90% of fenoxaprop-P-ethyl was absorbed within 6 hours after treatment and 30% of the absorbed was acropetally and basipetally translocated at 24 hours after treatment. Fenoxaprop-P-ethyl was rapidly transformed to its acid form, fenoxaprop(2-[4-(6-chloro-2-benzoxazolyloxy)phenoxy]propionic acid), which was subsequently metabolized to polar conjugates. However, changes in absorption, translocation, and metabolism of fenoxaprop-P-ethyl by bentazon treatment were not found in both species. Background activity of acetyl-CoA carboxylase(ACCase) in rice and barnyardgrass was 26.5 and 23.2nmol/min/mg, respectively. Concentration required to inhibit fifty percent enzyme activity$(I_{50})$ in vitro was 6.5~7.4${\mu}M$ of fenoxaprop-P-ethyl and more than 500${\mu}M$ of bentazon. There were no significant differences in $I_{50}$ value between two treatments of fenoxaprop-P-ethyl alone and its bentazon mixture. However, bentazon reduced ACCase activity in vivo and inhibited electron transport in chloroplast thylakoid. Based on the results obtained, it is concluded that the antagonistic effect of bentazon occurs due not to direct effect on target site of fenoxaprop-P-ethyl, but to indirect involvement in reducing herbicidal activity of fenoxaprop-P-ethyl through physiological disturbances caused by bentazone at whole chloroplast level.

• Korean Journal of Weed Science
• /
• v.31 no.2
• /
• pp.119-133
• /
• 2011

Sulfonylurea (SU)-resistant weeds include seven annual weeds such as Monochoria vaginalis, Scirpus juncoides and Cyperus difformis, etc., and three perennial weeds of Scirpus planiculmis, Sagittaria pigmaea and Eleocharis acicularis as of 2010 since identification Monochoria korsakowii in the reclaimed rice field in 1998. The Echinochloa oryzoides resistant to acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors has been confirmed in wet-direct seeding rice field of the southern province, Korea in 2009. In the beginning of occurrence of SU-resistant weeds the M. vaginalis, S. juncoides and C. difformis were rapidly and individually spreaded in different fields, however, theses resistant weeds have been occurring simultaneously in the same filed as time goes by. The resistant biotype by weed species demonstrated about 10- to 1,000-fold resistance, base on $GR_{50}$ (50% growth reduction) 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. In history of paddy herbicides in Korea, the introduction of SU herbicides including besulfuron-metyl and pyrazosulfuron-ethyl that control many troublesome weeds at low use rates and provide excellent crop safety gave farmers and many workers for herbicide business refreshing jolt. The products and applied area of SU-included herbicides have been rapidly increased, and have accounted for about 69% and 96%, respectively, in Korea. 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 direct-seeded rice led up to the resistance of E. oryzoides. Also, SU-herbicides like pyrazosulfuron-ethyl and imazosulfuron which are 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. 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, the early period, 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 filed. 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 2 leaf stage.

• Korean Journal of Weed Science
• /
• v.17 no.2
• /
• pp.192-198
• /
• 1997

This experiment was carried out to determine selectivity of herbicide cyhalofop-butyl ester on enzyme activity, biosynthesis of fatty acid and protein between rice and Echinochloa crus-galli. Activity of the acetyl-CoA carboxylase(ACCase) was inhibited greater in E. crus-galli than in rice by the treatment of cyhalofop-butyl ester. The ACCase activity in E. crus-galli was observed with $I_{50}$ at 1-2ppm of cyhalofop-butyl ester, while in rice only at above 10ppm. Cyhalofop-butyl ester also inhibited the biosynthesis of fatty acid by 61% of palmitic acid, 54% of linoleic acid and 41% of linolenic acid in E. crux-galli. In contrast, no significant difference of fatty acid content was observed in rice at 5DAT as compared with the untreated control. Protein patterns of rice between the herbicide treatment and the untreated control were not significantly different, but in E. crus-galli, 3 protein spots were disappeared in between 29KD and 45KD.