Bensulfuron Methyl Research Articles

Environmental fate of bensulfuron-methyl and MCPA in aerobic and anaerobic rice-cropping systems

Bensulfuron-methyl (BM) and 4-chloro-2-methylphenoxyacetic acid (MCPA) are herbicides widely used in rice agroecosystems, and are commonly found in their environments, especially in water resources. The objective of this study was to evaluate the sorption-desorption, leaching, and dissipation of BM and MCPA under aerobic and anaerobic rice cropping conditions. For this purpose, a three-year field experiment was conducted in SW Spain using four management systems: aerobic with sprinkler irrigation and tillage (ST), sprinkler irrigation and no-tillage (SNT), long-term sprinkler irrigation and no-tillage (SNTLT), and anaerobic with flooding and tillage (FT). At the end of the experiment, the partition coefficients (Kd-values) in ST were (2.7, 3.1, and 3.9) and (1.2, 1.5, and 1.9) times significantly lower than the values in {SNT, SNTLT, and FT} for BM and MCPA, respectively. Greater sorption was related to lower values of soil pH for both herbicides and to higher contents in humic acids for BM and fulvic acids for MCPA. The persistence was much longer for BM (t1/2 = 26.9–52.1 days) than for MCPA (t1/2 = 1.54–21.1 days) in all management systems, and both herbicides' dissipation rates were generally greater under aerobic than under anaerobic conditions. The mobility of MCPA was much greater than that of BM. Compared with SNT and SNTLT, leaching losses of the applied BM were greater by 51% for ST, and of the applied MCPA by 55% and 99% for ST and FT, respectively. Therefore, only aerobic rice production with no-tillage in the short- or long-terms could be considered as alternative management strategies with which to reduce water contamination by BM and MCPA in rice-growing environments.

The mechanism of bensulfuron-methyl complexation with \u03b2-cyclodextrin and 2-hydroxypropyl-\u03b2-cyclodextrin and effect on soil adsorption and bio-activity

In this work, the inclusion complexes of hydrophobic herbicide bensulfuron-methyl (BSM) with β-cyclodextrin (β-CD) and (2-hydroxypropyl)-β-CD (2-HP-β-CD) were prepared and characterized. Phase solubility study showed that both β-CD and 2-HP-β-CD increased the solubility of BSM. Three-dimensional structures of the inclusion complexes were simulated by the molecular docking method. The docking results indicated that guest BSM could enter into the cavities of host CDs, folded, and centrally aligned inside the inclusion complexes. The benzene ring of the guest molecule was close to the wide rim of the host molecules; the pyrimidine ring and side chains of the guest molecule were oriented toward the narrow rim of the host molecule. The inclusion complexes were successfully prepared by the coprecipitation method. The physiochemical characterization data of 1H NMR, FT-IR, XRD, and DSC showed that the guest and host molecules were well included. BSM had lower soil adsorption and higher herbicidal activity in the complexation form with β-CD or 2-HP-β-CD than in the pure form. The present study provides an approach to develop a novel CDs-based formulation for hydrophobic herbicides.

Sensitivity of Annual Weeds Against Metolachlor + Bensulfuron - Methyl Herbicide in Transplanted Rice


 Field trials were conducted at Bangladesh Rice Research Institute (BRRI), Gazipur during aman, 2014 and boro, 2014-15 to evaluate the efficacy of metolachlor + bensulfuron methyl 20% WP on weed suppression of transplanted rice. Metolachlor + bensulfuron methyl 20% WP @ 150, 190 and 230 g ha-1 were applied and pyrazosulfuran ethyl @ 125 g ha-1, weed free and unweeded control were the treatment variables. Visual observations indicated that this herbicide possesses high selectivity and not toxic to rice plants. The results revealed that the major weed flora associated with the transplanted rice was mainly comprised of two grasses, two sedges and three broadleaf in aman and two grasses, two sedges and two broadleaf in boro season. The most dominant weeds were Cyperus difformis, Echinochloa crus-galli, Scirpus maritimus and Monochoria vaginalis in both the growing seasons. Application of metolachlor + bensulfuron methyl 20% WP @ 190 g ha-1 was most effective to suppress weeds in both the seasons resulting in increased grain yield more than 40% as compared to unweeded control. Therefore, metolachlor + bensulfuron methyl 20% WP@ 190 g ha-1applied at one to two leaf stage of weed effectively controls the weed infestation in transplanted rice.
 Bangladesh Agron. J. 2018, 21(1): 61-70
 

Chemical Weed Control in Paddy Fields Inoculated with Azospirillum lipoferum

ABSTRACT: Herbicides, as a major part of weed control strategy in paddy fields, have different impact on growth and activity of soil-beneficial bacteria such as Azospirillum species. A field experiment was conducted at Sefid Rood Livestock and Agricultural Company, northern Iran, to investigate the possibility of chemical weed control in paddy fields inoculated with Azospirillum lipoferum. The experiment was designed in a factorial arrangement based on a randomized complete block with three replicates. The factors were Azospirillum application (inoculation with or without Azospirillum lipoferum) and weed management regime (butachlor application with supplementary hand-weeding, bensulfuron methyl application with supplementary hand-weeding, combination of butachlor and bensulfuron methyl application with supplementary hand-weeding, hand-weeding at 15, 30, and 45 days after transplanting, and no weeding [not weeded during the rice-growing period). The results showed that plants inoculated with A. lipoferum produced 19% higher grain yield compared to plants that were not inoculated. The highest grain yields were recorded for plots treated with butachlor with supplementary hand-weeding (4,512 kg ha-1) and for those treated with a combination of butachlor and bensulfuron methyl with supplementary hand-weeding (4500.5 kg ha-1). The lowest yield (3494.3 kg ha-1) was recorded for weedy plots. No significant interaction was detected between A. lipoferum application and weed management regime for grain yield, indicating that the herbicides had no adverse effect on the efficiency of A. lipoferum in promoting growth and grain yield of rice. There was no significant difference in the dry weights of weed between inoculated and non-inoculated plots. The dry weights of weed in hand-weeded and herbicide-treated plots were significantly lower than that of the weedy plot. In conclusion, the result of this experiment confirms the possibility of chemical weed control in paddy fields inoculated with A. lipoferum.

Developing dual herbicide tolerant transgenic rice plants for sustainable weed management

Herbicides are important constituents of modern integrated weed management system. However, the continuous use of a single herbicide leads to the frequent evolution of resistant weeds which further challenges their management. To overcome this situation, alternating use of multiple herbicides along with conventional weed-management practices is suitable and recommended. The development of multiple herbicide-tolerant crops is still in its infancy, and only a few crops with herbicide tolerance traits have been reported and commercialized. In this study, we developed transgenic rice plants that were tolerant to both bensulfuron methyl (BM) and glufosinate herbicides. The herbicide tolerant mutant variant of rice AHAS (Acetohydroxyacid synthase) was overexpressed along with codon optimized bacterial bar gene. The developed transgenic lines showed significant tolerance to both herbicides at various stages of plant development. The selected transgenic lines displayed an increased tolerance against 100 μM BM and 30 mg/L phosphinothricin during seed germination stage. Foliar applications further confirmed the dual tolerance to 300 μM BM and 2% basta herbicides without any significant growth and yield penalties. The development of dual-herbicide-tolerant transgenic plants adds further information to the knowledge of crop herbicide tolerance for sustainable weed management in modern agricultural system.

Performance of Pre- and Post-emergence herbicides in strip tillage Non-puddled transplanted Aman rice

A study was conducted on transplanted aman rice (cv. BINA dhan-7) in strip-tilled non-puddled field with some commonly used rice herbicides (pre-emergence: pyrazosulfuron-ethyl and butachlor, early post-emergence: orthosulfamuron and late post-emergence: acetochlor + bensulfuron methyl, butachlor + propanil and 2,4-D amine) applied singly or in sequences during 2013 and 2014 at field laboratory, Bangladesh Agricultural University, Mymensingh to evaluate the effect of those herbicides on weeds as well as growth and yield of aman rice in strip-tilled non-puddled condition. The study showed that herbicides significantly reduced weed density by 75-94% in 2013 and 46-98% in 2014 compared to the weedy check. Sole application of pre- or early post-emergence herbicide provided less weed control than sequential application of pre-, early post- and late post-emergence herbicides or application of pre- and late post-emergence herbicides. A wide range of sequential application of herbicide treatments has identified in the study that provided control on weed density and biomass by 49-98% and 56-95%, respectively. Application of pyrazosulfuron-ethyl followed by orthosulfamuron and butachlor + propanil was the most effective combination in this new rice establishment condition that controlled all types of weeds successfully and provided maximum grain yield (5.42 t ha-1 in 2013 and 6.18 t ha-1 in 2014) with highest economic return (Tk. 55930 ha-1 in 2013 and Tk. 69057 ha-1 in 2014). The study suggests economically beneficial some combinations of currently used herbicides for strip-tlled non-puddled transplanted aman rice that may help farmers to choose and rotate in the same land yearwise for obtaining optimum yield.Bangladesh J. Agril. Res. 42(4): 631-646, December 2017

Hydrolysis, adsorption, and biodegradation of bensulfuron methyl under methanogenic conditions

Bensulfuron methyl (BSM), one of the most widely used herbicides in paddy soils, is frequently detected in natural and artificial aquatic systems. However, BSM transformation under methanogenic conditions has not been given sufficient attention. In this study, BSM elimination and transformation by anaerobic enrichment cultures were investigated. The results showed that BSM can be mineralized to methane through hydrolysis, adsorption, and biodegradation under a methanogenic environment. The adsorption led to protein static quenching in the extracellular polymeric substances (EPSs) of the enrichment cultures. Specifically, BSM mainly reacted with the amine, amide, amino acid, and amino sugar functional groups in proteins. BSM hydrolysis and biodegradation occurred through the breakage of the sulfonylurea bridge and sulfonyl amide linkage. The cleavage of the sulfonylurea bridge occurred in both hydrolysis and biodegradation, while the cleavage of the sulfonyl amide linkage only occurred in hydrolysis. These results elucidated the complex transformation of BSM under methanogenic conditions, which will advance the studies on sulfonylurea herbicide biotransformation and hazard assessment in the environment.

Nicosulfuron Biodegradation by a Novel Cold-Adapted Strain Oceanisphaera psychrotolerans LAM-WHM-ZC.

Nicosulfuron is a common environmental pollutant, posing a great threat to aquatic systems and causing significant damage to crops. This study reported a cold-adapted strain Oceanisphaera psychrotolerans LAM-WHM-ZC, which efficiently degrades nicosulfuron over a wide range of temperatures (5 to 40 °C). The Box-Behnken design method was used to optimize the degradation conditions. O. psychrotolerans LAM-WHM-ZC can degrade 92.4% and 74.6% of initially supplemented 100 mg/L nicosulfuron under the optimum and low temperature of 18.1 and 5 °C, respectively, within 7 days. O. psychrotolerans LAM-WHM-ZC was found to be highly efficient in degrading cinosulfuron, chlorsulfuron, rimsulfuron, bensulfuron methyl, and ethametsulfuron methyl. Metabolites from nicosulfuron degradation were identified by UPLC-MS, and a possible degradation pathway was proposed. Furthermore, O. psychrotolerans LAM-WHM-ZC can also degrade nicosulfuron in soil; 78.6% and 67.4% of the initial nicosulfuron supplemented at 50 mg/kg were removed at 18.1 and 5 °C, respectively, within 15 days.

COMPARATIVE EFFICACY OF HERBICIDES IN WEED CONTROL AND ENHANCEMENT OF PRODUCTIVITY AND PROFITABILITY OF RICE

SUMMARYWeed management is the major challenge to the success of boro rice (rice grown during Dec–Jan to May–Jun, also known as summer rice) in Southern Asia. Herbicide seems to be a cost effective and strategic tool from an agronomic view point to control weeds; however, herbicide application can potentially interfere with soil enzyme activity and microbial biomass carbon (MBC). A field study was conducted in 2012/13 and 2013/14 to evaluate the performance of sole and combined application of different pre-emergence herbicides in comparison to manual weeding in boro rice. Lowest weed density, biomass and highest weed control efficiency (~83%) were recorded with the pyrazosulfuron ethyl, causing higher grain yield (6.7 Mg ha−1 in 2012/13 and 4.5 Mg ha−1 in 2013/14) than treatments with chlorimuron + metsulfuron-methyl, bensulfuron methyl + pretilachlor, butachlor fb 2,4D, butachlor and cono-weeder. Among, the herbicidal treatments butachlor caused lower grain yield and higher weed density and biomass when compared to the others. Although grain yield was highest in weed-free treatments but net returns and (B:C) benefit cost ratio was highest for pyrazosulfuron ethyl due to high cost of hand weeding. After 15 days of herbicide application, lowest microbial biomass carbon was recorded with bensulfuron methyl + pretilachlor, whereas lower values of dehydrogenase and fluorescein diacetate activities were observed with the application of chlorimuron + metsulfuron-methyl at 15 days after herbicide application. Our results suggest that pyrazosulfuron ethyl is one broad-spectrum and economically effective herbicide for controlling weeds as an alternative to labour consuming hand weeding in boro rice cultivation.

Residual Effect of Herbicides Applied in Unpuddled Transplanted Aman Rice on The Succeeding Crops Assessed by Bioassay Technique

The residual effect of eight herbicides (pendimethalin, pyrazosulfuron-ethyl, butachlor, pretilachlor, orthosulfamuron, acetochlor + bensulfuron methyl, butachlor + propanil and 2,4-D amine) was applied in unpuddled transplanted aman rice in aa weedy and a hand weeded controls, was evaluated for succeeding crops viz. wheat, lentil and sunflower by following bioassay technique. A study was conducted at Bangladesh Agricultural University, Mymensingh from November 2013 to January 2014 after harvest of unpuddled transplanted aman rice. All herbicides were imposed as weed management practice of unpuddled transplanted aman rice during July to August 2013. The experiment was laid out in a randomized complete block design (RCBD) with three replications. As a consequence, the residual effect of those herbicides on the succeeding wheat, lentil and sunflower crops was evaluated in term of germination, leaf chlorophyll content, seedling shoot length and dry matter. The results showed that seedling germination of all these succeeding crops in the herbicide treated plots did not differ significantly from those of weedy and hand weeded control plots. Moreover, leaf chlorophyll content, seedling shoot length and dry matter of wheat, lentil and sunflower were not adversely affected by any of the herbicide treatments imposed in aman rice. It was concluded that herbicides used in unpuddled transplanted aman rice had no residual effect on the germination and leaf chlorophyll content, seedling shoot length and dry matter of the succeeding wheat, lentil and sunflower crops.Bangladesh Agron. J. 2016 19(2): 95-103

Impact of different herbicides on transplanted basmati rice in a Typic Haplustept soil of Punjab, India

A field experiment was conducted to evaluate the impact off different herbicides on transplanted basmati rice in Typic Haplustept soils of Punjab during kharif season of 2015–16. The predominant weed species observed in experimental farm were Echinochloa crusgalli, Cynodon dactylon, Cyperus rotundus, Cyperus difformis and Eclipta alba. The results showed that the grasses were the predominant weed species followed by broadleaf weeds and sedges. Significantly lower weed density (7.3/m2) and weed dry weight/m2 (5.4 g) were recorded in hand weeded plot which remained at par with pre-emergence herbicide bensulfuron methyl @ 55 g a. i./ha. The highest weed control efficiency (97%) was obtained with hand weeding followed by bispyribac sodium 10 SC @ 30 g a. i./ha (93.8%). The maximum plant height (143.9cm), number of tillers per plant (34.6), number of panicles per plant (48.3), number of filled grains per panicle (114.3), 1000-grain weight (32 g), grain yield (5964 kg/ha), straw yield (6327 kg/ha) and harvest index (20.4%) were recorded in HW plots followed by bensulfuron methyl @ 55 g a. i./ha with plant height (114.9 cm), number of tillers/plant (32.6), number of panicles/plant (46), number of filled grains per panicle (103.6), 1000-grain weight (29.2 g), grain yield (5714 kg/ha), straw yield (6280 kg/ha) and harvest index (18.4%).

Bensulfuron-Methyl Treatment of Soil Affects the Infestation of Whitefly, Aphid, and Tobacco Mosaic Virus on Nicotiana tabacum.

Bensulfuron-methyl (BSM) is widely used in paddy soil for weed control. BSM residue in the soil has been known to inhibit the growth of sensitive crop plants. However, it is unknown whether BSM residue can affect the agrosystem in general. In this study, we have found significant effects of BSM on the infestation of Bemisia tabaci, Myzus persicae, and Tobacco mosaic virus (TMV) in Nicotiana tabacum. The soil was treated with BSM before the pest inoculation. The herbicide-treated tobaccos showed resistance to B. tabaci, but this resistance could not be detected until 15-day post-infestation when smaller number of adults B. tabaci appeared. In M. persicae assay, the longevity of all development stages of insects, and the fecundity of insects were not significantly affected when feeding on BSM-treated plants. In TMV assay, the BSM treatment also reduced virus-induced lesions in early infection time. However, the titer of TMV in BSM treated plants increased greatly over time and was over 40-fold higher than the mock-infected control plants after 20 days. Further studies showed that BSM treatment increased both jasmonic acid (JA) and salicylic acid (SA) levels in tobacco, as well as the expression of target genes in the JA and SA signaling pathways, such as NtWIPK, NtPR1a, and NtPAL. NtPR1a and NtPAL were initially suppressed after virus-inoculation, while NtRDR1 and NtRDR6, which play a key role in fighting virus infection, only showed up- or were down-regulated 20 days post virus-inoculation. Taken together, our results suggested that BSM residue in the soil may affect the metabolism of important phytohormones such as JA and SA in sensitive plants and consequently affect the plant immune response against infections such as whitefly, aphids, and viruses.

Residue of bensulfuron methyl in soil and rice following its pre- and post-emergence application

Bensulfuron methyl (BSM) is applied in rice to control a wide range of weeds due to low application rate and high efficiency. A study was conducted to evaluate residues of BSM in soil and rice plant at different doses as pre- and post-emergence application in transplanted rice. The quick easy cheap effective rugged safe (QuEChERS) method was evaluated for BSM residue extraction from different matrices. The limit of detection and limit of quantification was 0.005 and 0.01 µg/g, respectively in soil and rice plant. The average BSM recovery of 91.1, 82.8, 84.5 and 88.7% was obtained from soil, rice straw, grain and husk, respectively. Though, BSM residue was detected (0.011 to 0.017 μg/g) in soil at high dose, it was below maximum residue limit (0.01 μg/g) in rice grain at both the doses of BSM. Hence, the study revealed that the BSM can be safely applied to rice at recommended doses for weed control.

Optimization of derivatization procedure and gas chromatography-mass spectrometry method for determination of bensulfuron-methyl herbicide residues in water.

A simple and efficient technique based on liquid phase extraction with CH2Cl2 solvent followed by derivatization with (C2H5)2O·BF3 solution and confirmation analysis with GC-MS analytical method was developed for detecting the bensulfuron-methyl (BSM) residues in water. Box-Behnken response surface methodology was employed for optimization of the derivatization efficiency. According to the optimization model, the derivatization time of 45min, derivatization temperature at 55°C and 0.2mL (C2H5)2O·BF3 solvent were selected as the optimal derivatization condition for obtaining the maximum desirability of response. Method validation was performed at 6 working standard levels (0.05, 0.1, 0.2, 0.5, 1.0, 5.0μg/mL) and the linearity of the calibration curve was linear well over the 6 fortification levels with the squared correlation coefficient of determination r(2)=0.998 and the LOD was found to be 0.1μg/L for BSM herbicide. The mean value of BSM was detected from 0.0414 to 4.7542μg/mL at levels from 0.05 to 5μg/mL with the recoveries remained at the acceptable level (42.8-95.0%) with the RSD values from 3.5% to 6.2%, which is more accptable and desirable than the results obtained by LC methods. Moreover, the method allowed the determination of BSM residue in real paddy field water samples at concentrations between 0.0902 and 3.4605μg/L. Average recovery rates of the BSM spiked at levels 0.1, 0.2, 0.5, 1.0μg/mL into thirty water samples ranged from 74.1% and 94.1% with the relative standard derivation (RSD) values from 1.9% to 6.7%.

Cytochrome P450 CYP81A12 and CYP81A21 Are Associated with Resistance to Two Acetolactate Synthase Inhibitors in Echinochloa phyllopogon.

Previous studies have demonstrated multiple herbicide resistance in California populations of Echinochloa phyllopogon, a noxious weed in rice (Oryza sativa) fields. It was suggested that the resistance to two classes of acetolactate synthase-inhibiting herbicides, bensulfuron-methyl (BSM) and penoxsulam (PX), may be caused by enhanced activities of herbicide-metabolizing cytochrome P450. We investigated BSM metabolism in the resistant (R) and susceptible (S) lines of E. phyllopogon, which were originally collected from different areas in California. R plants metabolized BSM through O-demethylation more rapidly than S plants. Based on available information about BSM tolerance in rice, we isolated and analyzed P450 genes of the CYP81A subfamily in E. phyllopogon. Two genes, CYP81A12 and CYP81A21, were more actively transcribed in R plants compared with S plants. Transgenic Arabidopsis (Arabidopsis thaliana) expressing either of the two genes survived in media containing BSM or PX at levels at which the wild type stopped growing. Segregation of resistances in the F2 generation from crosses of R and S plants suggested that the resistance to BSM and PX were each under the control of a single regulatory element. In F6 recombinant inbred lines, BSM and PX resistances cosegregated with increased transcript levels of CYP81A12 and CYP81A21. Heterologously produced CYP81A12 and CYP81A21 proteins in yeast (Saccharomyces cerevisiae) metabolized BSM through O-demethylation. Our results suggest that overexpression of the two P450 genes confers resistance to two classes of acetolactate synthase inhibitors to E. phyllopogon. The overexpression of the two genes could be regulated simultaneously by a single trans-acting element in the R line of E. phyllopogon.

Expression of sulfur uptake assimilation-related genes in response to cadmium, bensulfuron-methyl and their co-contamination in rice roots

The responses of sulfur (S) uptake assimilation-related genes' expression in roots of two rice cultivars to cadmium (Cd), bensulfuron-methyl (BSM) and their co-contamination (Cd+BSM) were investigated by gene-chip microarray analysis and quantitative real-time PCR (QRT-PCR) technology. Treatments of Cd and Cd+BSM induced expression of sulfate transporter and permease genes, and promoted sulfate uptake in rice roots. Cd+BSM could alleviate Cd toxicity to cv. Fengmeizhan seedlings, probably due to Cd+BSM promoting greater S absorption by seedlings. Cd and Cd+BSM induced expression of sulfate assimilation-related genes, and thus activated the sulfur assimilation pathway. Cd and Cd+BSM induced expression of phytochelatin synthase and metallothionein genes, and induced expression of glutathione S-transferases (GSTs), glutathione synthase (GS) and S-containing antioxidation enzyme genes, which detoxified Cd2+. It is suggested that (to cope with the toxicity of Cd, BSM and their co-contamination) the S uptake and assimilation pathway was activated in rice roots by increased expression of related genes, thus enhancing the supply of organic S for synthesis of Cd or BSM resistance-related substances.

A Novel Rice Cytochrome P450 Gene, CYP72A31, Confers Tolerance to Acetolactate Synthase-Inhibiting Herbicides in Rice and Arabidopsis

Target-site and non-target-site herbicide tolerance are caused by the prevention of herbicide binding to the target enzyme and the reduction to a nonlethal dose of herbicide reaching the target enzyme, respectively. There is little information on the molecular mechanisms involved in non-target-site herbicide tolerance, although it poses the greater threat in the evolution of herbicide-resistant weeds and could potentially be useful for the production of herbicide-tolerant crops because it is often involved in tolerance to multiherbicides. Bispyribac sodium (BS) is an herbicide that inhibits the activity of acetolactate synthase. Rice (Oryza sativa) of the indica variety show BS tolerance, while japonica rice varieties are BS sensitive. Map-based cloning and complementation tests revealed that a novel cytochrome P450 monooxygenase, CYP72A31, is involved in BS tolerance. Interestingly, BS tolerance was correlated with CYP72A31 messenger RNA levels in transgenic plants of rice and Arabidopsis (Arabidopsis thaliana). Moreover, Arabidopsis overexpressing CYP72A31 showed tolerance to bensulfuron-methyl (BSM), which belongs to a different class of acetolactate synthase-inhibiting herbicides, suggesting that CYP72A31 can metabolize BS and BSM to a compound with reduced phytotoxicity. On the other hand, we showed that the cytochrome P450 monooxygenase CYP81A6, which has been reported to confer BSM tolerance, is barely involved, if at all, in BS tolerance, suggesting that the CYP72A31 enzyme has different herbicide specificities compared with CYP81A6. Thus, the CYP72A31 gene is a potentially useful genetic resource in the fields of weed control, herbicide development, and molecular breeding in a broad range of crop species.

Anion Exchange Solid-Phase Extraction Combined with High Performance Liquid Chromatography to Determine Bensulfuron Methyl in Wheat and Soil

Anion Exchange Solid-Phase Extraction Combined with High Performance Liquid Chromatography to Determine Bensulfuron Methyl in Wheat and Soil

Harmful effects and chemical control study of Mikania micrantha H.B.K in Yunnan, Southwest China

Invasive alien species Mikania micrantha, which originated from Central and South America, has spread quickly and become one of the most seriously invasive weedy species in Yunnan Province, Southwest of China. The harmful effects of this plant on major cash crops and local plant communities have been surveyed in 50 townships of 6 counties of Yunnan Province since 2006. Moreover, bioactivity and selectivity of 20 types of herbicides on M. micrantha and farming crops have been tested and analyzed since 2007. The results showed that M. micrantha is mostly distributed in subtropical and tropical areas of Yunnan, such as Lincang District, Baoshan District and Dehong Prefecture. The species has resulted in a series of negative impacts on farming cash crops and local plant communities. Compared with the control effects of 20 soil and foliar-applied herbicides, soil-applied herbicides Atrazine, Bensulfuron methyl and Prometryne have higher bioactivity and selectivity to M. micrantha germination and seedling. Foliar-applied herbicides Sulfometuron methyl, Starane and Glyphosate have better control efficiency on M. micrantha growth, but the security is low. As a result, it recommends that Atrazine should be used for sugarcane, orchard and rubber land, Glyphosate for non farming land and rubber land, Sulfometuron methyl for forest land, and 2, 4-D for maize land, respectively. Key words: Mikania micrantha, crop yield loss, plant community, chemical control, Yunnan Province.

Characterization of sulfonylurea-resistant Schoenoplectus juncoides having a target-site Asp376Glu mutation in the acetolactate synthase

Schoenoplectus juncoides, a noxious weed for paddy rice, is known to become resistant to sulfonylurea (SU) herbicides by a target-site mutation in either of the two acetolactate synthase (ALS) genes (ALS1 and ALS2). SU-resistant S. juncoides plants having an Asp376Glu mutation in ALS2 were found from a paddy rice field in Japan, but their resistance profile has not been quantitatively investigated. In this study, dose–response of the SU-resistant accession was compared with that of a SU-susceptible accession at in vivo whole-plant level as well as at in vitro enzymatic level.In whole-plant tests, resistance factors (RFs) based on 50% growth reduction (GR50) for imazosulfuron (ISF), bensulfuron-methyl (BSM), metsulfuron-methyl (MSM), bispyribac-sodium (BPS), and imazaquin (IMQ) were 176, 40, 14, 5.2 and 1.5, respectively. Thus, the accession having an Asp376Glu mutation in ALS2 was highly resistant to the three SU herbicides and moderately resistant to BPS, but was not substantially resistant to IMQ. This is slightly different from the earlier results reported from other weeds with an Asp376Glu mutation, in which the mutation confers resistance to broadly all the chemical classes of ALS-inhibiting herbicides.In enzymatic tests, ALS2 of S. juncoides was expressed in E. coli; the resultant ALS2 was subjected to an in vitro assay. RFs of the mutated ALS2 based on 50% enzymatic inhibition (I50) for ISF, BSM, MSM, BPS, and IMQ were 3699, 2438, 322, 80, and 4.8, respectively. The RFs of ALS2 were highly correlated with those of the whole-plant; this suggests that the Asp376Glu mutation in ALS2 is a molecular basis for the whole-plant resistance. The presence of two ALS genes in S. juncoides can at least partially explain why the whole-plant RFs were less than those of the expressed ALS2 enzymes.