Imidazolinone Herbicides Research Articles

Evaluation of ALS-Resistant Yellow Nutsedge (Cyperus esculentus) in Georgia Peanut

Abstract Accounting for 53% of United States peanuts (Arachis hypogaea L.), Georgia is the top peanut-producing state with approximately 1.42 billion kg produced in 2023. Peanut producers often use the ALS imidazolinone herbicide imazapic but reduced yellow nutsedge (Cyperus esculentus L.) control was reported in Georgia peanuts after four-years of continuous imazapic use. This study aimed to determine the level of resistance (LD50, I50, and GR50), potential cross-resistance for the suspected resistant population, and identify the associated genetic mutations conferring resistance. A susceptible biotype was treated with 0, 0.0088, 0.0175, 0.035, 0.07, 0.14, 0.28, and 0.56 kg ai ha-1, and a resistant biotype was sprayed with 0, 0.07, 0.14, 0.28, 0.56, 1.13, 2.26, and 4.5 kg ai ha-1 of imazapic. To determine if the suspected resistant biotype was cross-resistant to halosulfuron-methyl, an ALS herbicide used to control nutsedge spp., both biotypes were treated with 0, 0.0117, 0.0233, 0.0466, 0.0933, 0.187, 0.373, and 0.746 g ai ha-1 of halosulfuron-methyl. Plants were rated for injury 7, 14, and 28 days after treatment (DAT), and above-ground biomass harvested at 28 DAT. For imazapic, LD50 was 0.041 and 1.503 kg ai ha-1 and the GR50 was estimated to be 0.0128 and 1.853 kg ai ha-1 for Sus and Res biotypes, respectively, indicating 36 and 145-fold increase in resistance of the Res biotype for I50 and GR50, respectively. Both biotypes responded similarly to applications of halosulfuron-methyl, with biomass reductionat rates greater than 0.023 kg ai ha-1. Transcriptome profiles revealed a mutation in the target-site gene of the resistant biotype, causing an amino acid substitution from Alanine to Valine at position 205 (Ala205Val). Growers should continue to rotate chemistries and implement integrated weed management approaches for control of C. esculentus as the use of imazapic over consecutive years has led to resistance in C. esculentus.

Combining capillary electrophoresis and chemometric tools for the straightforward determination of imidazolinone herbicides in plant-based milks.

Highly polar herbicides, such as imidazolinones, are used for weed control to increase agricultural productivity and crop quality. However, their misapplication can lead to residues in ready-to-eat food with a potential health risk for consumers. Hence, the fast determination of these herbicides is necessary for timely action. In this work, an eco-friendly method based on capillary zone electrophoresis combined with chemometrics was used for the determination of imazapyr and imazamox in vegetable-based beverages such as soy and quinoa milk. The analytical strategy consisted of only three steps: (i) protein precipitation prior to sample injection (ii) data pre-processing to reduce the background and make corrections on electrophoretic times shift, and (iii) resolution of fully overlapped capillary electrophoresis (CE) peaks by the well-known partial least square (PLS) algorithm, which extracts quantitative information attributed to the analytes. The method was successfully applied in the concentration range between 1.00 and 100 μg L-1 with coefficient of determination of the calibration (R2 cal) and prediction (R2 pred) > 0.90, residual prediction deviation of calibration (RPDcal) and of prediction (RPDpred) > 3, and relative error of prediction (REP) > 11 in the analyzed sample matrices, in the three built methods (quinoa samples, soy samples, and joint quinoa and soy samples). The proposed methodology offers a simple and quick alternative for determining imidazolinones at trace concentrations in vegetable beverages, such as quinoa and soy milk, without complex sample preparation. The results were consistent with those obtained using more complex techniques, confirming the applicability of this method. © 2024 Society of Chemical Industry.

3D structure of acetolactate synthase explains why the Asp-376-Glu point mutation does not give the same resistance level to different imidazolinone herbicides

Resistance to ALS-inhibiting herbicides has dramatically increased worldwide due to the persisting evolution of target site mutations that reduce the affinity between the herbicide and the target. We evaluated the effect of the well-known ALS Asp-376-Glu target site mutation on different imidazolinone herbicides, including imazamox and imazethapyr. Greenhouse dose response experiments indicate that the Amaranthus retroflexus biotype carrying Asp-376-Glu was fully controlled by applying the field recommended dose of imazamox, whereas it displayed high level of resistance to imazethapyr. Likewise, Sorghum halepense, carrying Asp-376-Glu showed resistance to field recommended doses of imazethapyr but not of imazamox. Biochemical inhibition and kinetic characterization of the Asp-376-Glu mutant enzyme heterologously expressed using different plant sequence backbones, indicate that the Asp-376-Glu shows high level of insensitivity to imazethapyr but not to imazamox, corroborating the greenhouse results. Docking simulations revealed that imazamox can still inhibit the Asp-376-Glu mutant enzyme through a chalcogen interaction between the oxygen of the ligand and the sulfur atom of the ALS Met200, while imazethapyr does not create such interaction. These results explain the different sensitivity of the Asp-376-Glu mutation towards imidazolinone herbicides, thus providing novel information that can be exploited for defining stewardship guidelines to manage fields infested by weeds harboring the Asp-376-Glu mutation.

First case of evolved herbicide resistance in the holoparasite sunflower broomrape, Orobanche cumana Wallr.

The development and commercialisation of sunflower varieties tolerant to acetolactate synthase (ALS)-inhibiting herbicides some 20 years ago provided farmers with an alternative method for the cost-effective control of Orobanche cumana. In 2020, however, two independent sunflower broomrape populations from Drama (GR-DRA) and Orestiada (GR-ORE), Greece, were reported to be heavily infested with O. cumana after application of the ALS-inhibiting herbicide imazamox. Here we have investigated the race of GR-DRA and GR-ORE and determined the basis of resistance to imazamox in the two Greek O. cumana samples. Using a set of five diagnostic sunflower varieties characterised by different resistant genes with respect to O. cumana infestation, we have clearly established that the GR-ORE and GR-DRA populations belong to the invasive broomrape races G and G+, respectively. Live underground tubercles and emerged shoots were identified at the recommended field rate of imazamox for GR-DRA and GR-ORE but not for two other standard sensitive populations in a whole plant dose response test using two different herbicide-tolerant sunflower hybrids as hosts. Sequencing of the ALS gene identified an alanine 205 to aspartate mutation in all GR-ORE samples. Most GR-DRA tubercles were characterised by a second serine 653 to asparagine ALS mutation whilst a few GR-DRA individuals contained the A205D mutation. Mutations at ALS codons 205 and 653 are known to impact on the binding and efficacy of imazamox and other imidazolinone herbicides. The knowledge generated here will be important for tracking and managing broomrape resistance to ALS-inhibiting herbicides in sunflower growing regions.

Phenotypic Characteristics and Occurrence Basis of Leaf Necrotic Spots in Response of Weedy Rice to Imazethapyr.

Weedy rice is the most challenging weed species to remove in rice production. We found a novel phenotype of seedling leaves which rapidly generates necrotic spots in response to imidazolinone herbicides in weedy rice, but its influencing factors and formation basis are still unknown. In this study, we used the leaf necrotic spot-producing type of weedy rice as the material. First, leaf necrotic spots were defined as physiological and vacuole-mediated cell necrosis by microscopic examination. The imazethapyr concentration was positively correlated with the degree of necrotic spots occurring, while the action site was in accordance with necrosis using herbicide stability tests combined with fluorescence parameters. Furthermore, transcriptome analysis revealed significant differences in the gene expression of endoplasmic reticulum stress and the lipid metabolism membrane structure damage pathway during necrosis, as confirmed by transmission electron microscopy. The light-temperature test also showed that high temperature and intense light could promote the appearance of necrotic spots. These experimental results are helpful in clarifying the process and basis of imazethapyr in inducing the rapid generation of necrotic spots in rice leaves and providing new insight into understanding the mechanism of response to imidazolinone herbicides and the control of weedy rice.

Investigation of Imidazolinone Herbicide Resistance Gene with KASP Markers for Japonica/Geng Rice Varieties in the Huanghuaihai Region of China.

Rice is a staple food for more than half of the global population due to its food security and sustainable development. Weeds compete with crops for sunlight and indispensable nutrients, affecting the yield and quality of crops. Breeding herbicide-tolerant rice varieties paired with herbicide application is expected to help with weed control. In this study, 194 Japonica/Geng rice varieties or lines collected from the Huanghuaihai region of China were screened by Kompetitive Allele-Specific PCR (KASP) markers based on four mutation sites within OsALS1 (LOC_Os02g30630), which is the target of imidazolinone (IMI) herbicides. Only the OsALS1627N haplotype was identified in 18 varieties, including the previously reported Jingeng818 (JG818), and its herbicide resistance was validated by treatment with three IMIs. To investigate the origin of the OsALS1627N haplotype in the identified varieties, six codominant PCR-based markers tightly linked with OsALS1 were developed. PCR analysis revealed that the other 17 IMI-tolerant varieties were derived from JG818. We randomly selected three IMI-tolerant varieties for comparative whole-genome resequencing with known receptor parent varieties. Sequence alignment revealed that more loci from JG818 have been introduced into IMI-tolerant varieties. However, all three IMI-tolerant varieties carried clustered third type single nucleotide polymorphism (SNP) sites from unknown parents, indicating that these varieties were not directly derived from JG818, whereas those from different intermediate improved lines were crossed with JG818. Overall, we found that only OsALS1627N from JG818 has been broadly introduced into the Huanghuaihai region of China. Additionally, the 17 identified IMI-tolerant varieties provide alternative opportunities for improving such varieties along with other good traits.

Transcriptomic and metabolomic analysis provides insight into imazethapyr toxicity to non-target plants.

Imazethapyr is a widely used imidazolinone herbicide worldwide, and its potential adverse effects on non-target plants have raised concerns. Understanding the mechanisms of imazethapyr phytotoxicity is crucial for its agro-ecological risk assessment. Here, the comprehensive molecular responses and metabolic alterations of Arabidopsis in response to imazethapyr were investigated. Our results showed that root exposure to imazethapyr inhibited shoot growth, reduced chlorophyll contents, induced photoinhibition and decreased photosynthetic activity. By non-target metabolomic analysis, we identified 75 metabolites that were significantly changed after imazethapyr exposure, and they are mainly enriched in carbohydrate, lipid and amino acid metabolism. Transcriptomic analysis confirmed that imazethapyr significantly downregulated the genes involved in photosynthetic electron transport and the carbon cycle. In detail, 48 genes in the photosynthetic lightreaction and 11 genes in Calvin cycle were downregulated. Additionally, the downregulation of genes related to electron transport in mitochondria provides strong evidence for imazethapyr inhibiting photosynthetic carbon fixation and cellular energy metabolism as one of mechanisms of toxicity. These results revealed the molecular and metabolic basis of imazethapyr toxicity on non-target plants, contributing to environmental risk assessment and mitigate negative impact of imazethapyr residues in agricultural soils.

Registration of ‘CLL17’ rice

Abstract‘CLL17’ (Reg. no. CV‐160; PI 693941), a high‐yielding long‐grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the H. Rouse Caffey Rice Research Station near Crowley, LA, and approved for release in 2020. CLL17 contains the herbicide‐resistant gene for use in the Clearfield rice production system. The Clearfield rice production system is defined as the brand of rice cultivars that are tolerant to imidazolinone herbicides. CLL17 was derived from the cross ‘CL131’/‘Trenasse’. It showed good yield potential and favorable agronomic characteristics in the 2015 Clearfield Preliminary Yield Trial. In 2016, it was evaluated in the uniform regional rice nursery trial across four southern states. From 2017 to 2022, CLL17 was evaluated in 50 replicated trials across 10 locations in Louisiana. Three high‐yielding commercial cultivars were included as checks: ‘Cheniere’, ‘CL153’, and ‘CL111’. The grain yield of CLL17 was 9.0 t ha−1 compared with 8.9 t ha−1 for CL153, 8.3 t ha−1 for CL111, and 8.2 t ha−1 for Cheniere across 25 commercial advanced trials from 2017 to 2020. CLL17 had a similar plant height to CL111, 2‐cm taller than CL153, and 5‐cm taller than Cheniere. It exhibits typical US long‐grain rice cooking quality with intermediate amylose and gel temperature. CLL17 is susceptible to sheath blight [caused by Rhizoctonia solani Kuhn ], resistant to Cercospora spp., leaf blast [caused by Magnaporthe grisea (T.T. Hebert)], and neck blast, and moderately susceptible to bacterial panicle blight (caused by Burkholderia glumae).

Gene flow and spontaneous mutations are responsible for imidazolinone herbicide-resistant weedy rice (Oryza sativa L.)

For more than two decades, weedy rice (Oryza sativa L.) has been controlled in rice fields by using imidazolinone (IMI) herbicide-resistant rice technology (Clearfield®). Outcrossing in weedy rice populations and spontaneous mutations are potential problems with herbicide-resistant crop management technologies, such as the IMI-resistant rice. The aim of this study was to characterize the mechanism of IMI herbicide resistance in weedy rice through dose-response bioassay study and evaluating amino acid substitutions in acetolactate synthase (ALS) protein. A total of 118 suspected IMI-resistant weedy rice samples, which survived in the field after an IMI herbicide application, were collected at harvest time from Türkiye in 2020 and 2021. Single-dose imazamox application experiment revealed that 38 plants survived herbicide treatment. The imazamox resistance of the surviving plants was confirmed by dose-response experiment. ALS gene region underwent a sanger DNA partial sequencing. No substitution was found in 10 samples, however, amino acid substitutions were found in 26 samples with S563N, one sample with S653T, and one sample with E630D. The S653N point is the same substitution point that serves as the origin of resistance for the Clearfield® rice varieties that are commonly cultivated in the region. It has been hypothesized that the gene flow from IMI-resistant rice may be the cause of resistance in the IMI resistant weedy rice samples with S653N. The other substitution, S653T, were considered spontaneous mutation to IMI resistance. Interestingly, the S653T mutation was detected for the first time in weedy rice. The mechanism of resistance of 10 resistant weedy rice was not confirmed in this study, however, it may be a non-target resistance or another mutation point in target site, but evidently, they did not acquire resistance by gene flow from IMI-resistant rice. It has been concluded that the effectiveness of IMI-resistant rice technology in controlling weedy rice has drastically decreased due to possible gene flow, spontaneous mutation and non-target resistance. In addition to cultural controls like clean seed, clean machinery and crop rotation, other herbicide-tolerant rice systems such as Provisia® and Roxy-RPS® rice are needed to create a diverse weedy rice management ensemble available for rice production and move towards sustainable rice farming.

Форпост КЛ – первый отечественный сорт ярового рапса, устойчивый к имидазолиноновым гербицидам

A spring rapeseed cultivar Forpost KL has been developed during the period of 2009–2019 by an individual selection method in F2 from ESI-No. 65/2009 × Luch hybrid combination. That was the first Russian spring rapeseed cultivar resistant to imidazolinone herbicides. In 2015–2019, in the competitive crop variety testing conducted in the All-Russian Research Rapeseed Institute, the cultivar Forpost KL exceeded the standard Rif on seed yield by 0.15 t/ha (by 7.6 %), on oil yield – by 0.07 t/ha, and its glucos-inolate content in seeds was lower by 2.6 µmol/g. Forpost KL has been included into the State Register of breeding achievements (Patent No. 12408) and approved for production in the North-West (2), Central (3), Volga-Vyatka (4), Central Black Earth (5), Middle Volga (7), Ural ( 9), West Siberian (10), and East Siberian (11) regions from 2022.

Point mutations including a novel Pro-197-Phe mutation confer cross resistance to acetolactate synthase (ALS) inhibiting herbicides in Lactuca serriola in Australia.

Control of prickly lettuce has become increasingly difficult for lentil growers in southern Australia due to widespread resistance to common herbicides, a lack of alternative herbicide options, and prolific production of highly mobile seed. This study aimed to quantify ALS-inhibiting herbicide resistance in the Mid North (MN) and Yorke Peninsula (YP) of South Australia, characterise the resistance mutations present, and investigate population structure and gene flow in this species. Resistance was identified in all populations tested, with average survival of 92% to chlorsulfuron and 95% to imazamox + imazapyr. Five different amino acid substitutions were identified at Proline-197 of the ALS gene. There was no significant difference in the LD50 between plants with these five different substitutions when treated with metsulfuron-methyl, however, imidazolinone resistance level was higher in plants with a phenylalanine substitution and lower in plants with a serine. Population structure based on 701 SNPs and 271 individuals provided evidence for both the independent evolution of the same mutation in different populations, as well as frequent short to medium distance dispersal accompanied by occasional long-distance dispersal events. The overall inbreeding coefficient (FIS ) was calculated at 0.5174, indicating an intermediate level of outcrossing despite the cross-pollination experiment showing only low outcrossing. In the structure analyses, most individuals from YP were assigned to a single cluster, whereas most individuals from MN were assigned 50% to each of two clusters, indicating some genetic differences between these two regions, but also evidence for dispersal between them. Use of imidazolinone herbicides has selected for mutations conferring higher levels of resistance, such as the Pro-197-Phe mutation, and resulted in further spread of resistance in this species. This article is protected by copyright. All rights reserved.

Imazethapyr disrupts plant phosphorus homeostasis and acquisition strategies

The deficiency of essential mineral nutrients caused by xenobiotics often results in plant mortality or an inability to complete its life cycle. Imazethapyr, a widely utilized imidazolinone herbicide, has a long-lasting presence in the soil-plant system and can induce toxicity in non-target plants. However, the effects of imazethapyr on mineral nutrient homeostasis remain poorly comprehended. In this study, Arabidopsis seedlings exposed to concentrations of 4 and 10 μg/L imazethapyr showed noticeable reductions in shoot development and displayed a distinct dark purple color, which is commonly associated with phosphorus (P) deficiency in crops. Additionally, the total P content in both the shoots and roots of Arabidopsis significantly decreased following imazethapyr treatment when compared to the control groups. Through the complementary use of physiological and molecular analyses, we discovered that imazethapyr hinders the abundance and functionality of inorganic phosphorus (Pi) transporters and acid phosphatase. Furthermore, imazethapyr impairs the plant's Pi-deficiency adaptation strategies, such as inhibiting Pi transporter activities and impeding root hair development, which ultimately exacerbate P starvation. These results provide compelling evidence that residues of imazethapyr have the potential to disrupt plant P homeostasis and acquisition strategies. These findings offer valuable insights for risk assessment and highlight the need to reconsider the indiscriminate use of imazethapyr, particularly under specific scenarios such as nutrient deficiency.

Registration of ‘Successor’ barley: A two‐row, spring‐habit, feed cultivar with tolerance to imidazolinone herbicides and adaptation to dryland production

Abstract‘Successor’ (Reg. no. CV‐377, PI 702593), experimental designation DH190481, is a two‐row spring barley (Hordeum vulgare L.) released by Oregon Agricultural Experiment Station in 2023. It is notable for tolerance to imidazolinone herbicides and can be planted in a rotation with crops that are treated with these chemicals. Successor is well adapted to dryland production in the Pacific Northwest and is being released as a feed cultivar. This assessment evaluated the cultivar in a multi‐environment cultivar trial in eastern Oregon and Washington and in an on‐farm trial at a commercial partner. It showed strong performance and matched or exceeded expectations set by the only other currently available imidazolinone‐tolerant cultivar adapted to the target growing region, Survivor.

A nonsynonymous mutation in an acetolactate synthase gene (Gh_D10G1253) is required for tolerance to imidazolinone herbicides in cotton

BackgroundHerbicide tolerance in crops enables them to survive when lethal doses of herbicides are applied to surrounding weeds. Herbicide-tolerant crops can be developed through transgenic approaches or traditional mutagenesis approaches. At present, no transgenic herbicide tolerant cotton have been commercialized in China due to the genetically-modified organism (GMO) regulation law. We aim to develop a non-transgenic herbicide-tolerant cotton through ethyl methanesulfonate (EMS) mutagenesis, offering an alternative choice for weed management.ResultsSeeds of an elite cotton cultivar Lumianyan 37 (Lu37) were treated with EMS, and a mutant Lu37-1 showed strong tolerance to imidazolinone (IMI) herbicides was identified. A novel nonsynonymous substitution mutation Ser642Asn at acetolactate synthase (ALS) (Gh_D10G1253) in Lu37-1 mutant line was found to be the potential cause to the IMI herbicides tolerance in cotton. The Ser642Asn mutation in ALS did not present among the genomes of natural Gossypium species. Cleaved amplified polymorphic sequence (CAPS) markers were developed to identify the ALS mutant allele. The Arabidopsis overexpressing the mutanted ALS also showed high tolerance to IMI herbicides.ConclusionThe nonsynonymous substitution mutation Ser642Asn of the ALS gene Gh_D10G1253 is a novel identified mutation in cotton. This substitution mutation has also been identified in the orthologous ALS genes in other crops. This mutant ALS allele can be used to develop IMI herbicide-tolerant crops via a non-transgenic or transgenic approach.Graphical abstract

OIL CONTENT OF SUNFLOWER GENOTYPES IN YEARS 2020 AND 2021 IN FUNDULEA LOCATION

At NARDI Fundulea, sunflower breeding program is focused for developing sunflower hybrids with high seed oil content, with resistance at main pathogens such as Plasmoparahalstedii, Sclerotiniasclerotiorum, Phomopsishelianthi and with resistance at sulfonylurea herbicides (SU) and to imidazolinone (CL Plus) herbicides.
 Temperature and precipitation influence seed oil content of sunflower genotypes in booth years 2020 and 2021, in Fundulea location. The amount of precipitation during the sunflower vegetation period from April to September, in both years 2020 (248.6 mm) and 2021 (273.2 mm), was lower than the 60-year average amount (351.8mm). 
 Average seed oil content, in year 2020, was included in the values of 48.63% at sunflower experimental hybrid H54CLP in Clearfield Plus system and 51.79% at sunflower experimental hybrid H87SU in Express Sun system and in year 2021, was included in the values of 41.69% at H54CLP and 50.56% at H87SU. Agricultural year (2020, 2021), sunflower hybrid and their interaction, influence significant positive the oil content of seed. 
 In year 2020 in Fundulea location, pathogen Plasmoparahalstedii has an attack degree between 3% at H76SU, H50CLP and 17% at H54CLP and in year 2021, between 6% at H76SU, H50CLP and 23% at H54CLP.

Efficient removal of Spartina alterniflora with low negative environmental impacts using imazapyr

Invasion by smooth cordgrass (Spartina alterniflora Loisel) has greatly impacted the intertidal ecosystems of China. Worldwide, chemical control is the most widely used method to control Spartina species, but it has not been widely implemented along the Chinese coast due to concerns about the potential impacts of herbicide residues on the environment and organisms. Macrobenthos, both natural and cultured on intertidal mudflats, is an important seafood resource, so human food safety is a particular concern. Here we tested the effectiveness of imazapyr (an imidazolinone herbicide inhibiting the synthesis of branched-chain amino acids) in controlling S. alterniflora from August 2020 to June 2021 on the Jiangsu Coast, an area severely impacted by S. alterniflora. We used two different concentrations of the herbicide and monitored the density of S. alterniflora seedlings and flower spikelets, the effects of herbicide use on macrobenthos, and residues in organisms and the environment at different times post-application. Ten months after application, imazapyr had killed all plants and within 30 days it inhibited the two reproductive processes of germination and flowering; there were no significant differences between the two concentrations used. Imazapyr residues were detected in the environment for up to 14 days post-application, but at very low concentrations and exponentially decreased with time. No residues were found in any macrobenthos. Imazapyr use did not result in a reduction of macrobenthos density. We conclude that the herbicide imazapyr effectively removes S. alterniflora with little collateral damage to other organisms and the environment. However, in view of the relatively small scale of our trials and the great extent of S. alterniflora in many sites in China, we recommend that larger scale field trails be conducted to assess any potential adverse effects when imazapyr is used at a landscape level.

Toxicity and selective mechanism of imazamox by weedy rice and imidazolinone‐resistant rice in China

AbstractWeedy rice (Oryza spp.) is a notorious weed in direct‐seeding paddy fields. Because it has anatomical and physiological traits similar to those of cultivated rice, no selective herbicide is effective in controlling weedy rice growing among conventional rice cultivars. Imidazolinone (IMI)‐resistant rice lines JD372 and JJ818 have been planted with imazamox to control weedy rice in Jiangsu and Shanghai, China. Whole‐plant dose–response analysis showed that imazamox exhibited high efficacy against three populations of weedy rice. The ED90 of weedy rice populations FN‐5, GY‐8, and HY‐3 were 46.87, 61.43, and 52.17 g a.i. ha−1, respectively, close to the recommended field dose (50 g a.i. ha−1) of imazamox. Conversely, the ED10 values of JD372 and JJ818 were slightly lower than 50 g a.i. ha−1. These findings indicate that imazamox can control weedy rice production in JD372 and JJ818 fields. The acetolactate synthase (ALS) sensitivity of JD372 in vitro was 1714.89‐fold lower to imazamox than was that of FN‐5. ALS gene sequencing revealed a Ser653Asn point mutation—a common mutation that confers resistance to IMI herbicides in JD372. In addition, higher ALS expression levels in JD372 were found at 24 and 72 h after imazamox treatment. ALS overexpression might partially compensate for the ALS activity of JD372 that was suppressed by imazamox.

Bio-efficacy of imidazolinones in weed control in a tropical paddy soil amended with optimized agrowaste-derived biochars.

Biochar is a black carbon sorbent that has the ability to stabilize organic substances in soil and, therefore, the potential to reduce their bio-availability. This sustainable material can be produced from locally-available agro wastes. The present study, for the first time, investigated the effects of biochars produced from oil palm empty fruit bunches (EFB) and rice husk (RH) on the efficiency of imazapic and imazapyr (two polar members of imidazolinone herbicides) as well as Onduty®, a mixture of them. It was executed in a Malaysian paddy field soil during a 30-day greenhouse experiment. The presence of optimized EFB and RH biochars in the heavy soil generally increases weed seeds germination and plants growth due to stabilization of the herbicides. The effect of EFB biochar was found higher than RH biochar having a higher affinity to the herbicides. An increase in the biochars application rates enhanced their effects as a soil modifier. Differences were more significant in the higher herbicides doses. Efficacies of all the herbicides were generally decreased in the biochar-amended soils. In the presence of 0.5% biochar in soil, the GR50 values for all herbicides were almost similar to biochar-free soil. In a 1.0% biochar-soil mixture, GR50 values of the herbicides increased by about 1.5 times. Bio-efficacies of the herbicides decreased by around 2.0 times as the biochar application rate enhanced to 2.0%. The greatest GR50 values were obtained in the presence of 4.0% biochar in the soils and were about 7.0-8.5 folds, indicating the high capability of amended soil in the stabilization of the herbicides. The findings of this study can help to reduce imidazolinones' pollution and, in this way, prevent the threats of their residues to the environment.

Structure characterization of Imidazolinone–Fe(II) complex by using multiple analytical and spectroscopic methods

Imazamox, one of imidazolinone herbicides, was found can chelate with Fe(II) in surface water enviroment to form imazamox-Fe(II) complex. By using EDS elemental analysis, HR-ESI-MS and JOB's curves, the complex was characterized as two molecule imazamox coordinated with one ferrous iron, besides, multiple analytical and spectroscopic methods, such as UV-vis, FT-IR, Raman and control experiments were conducted, the function group involved in coordination was determined, and the structure detail of imazamox-Fe(II) complex was proposed as four N atoms from two different imazamox ions (two N atoms from two pyridyl rings and the other two N atoms from two oxo-imidazole rings) and two O atoms from two different carboxylate groups to complete a 6-coordinate mode of Fe(II). Based on the finding, the influence of imidazolinone herbicides on available ferrous iron in soil was also discussed.

Development of Simultaneous Analytical Method for Imidazolinone Herbicides from Livestock Products by UHPLC-MSMS.

A simultaneous analytical method, which used LC/MSMS for imidazolinone herbicides from livestock products (egg, milk, beef, pork, and chicken) for monitoring, was developed with a QuEChERS preparation. A weighed sample (5 g) in a 50 mL conical tube was added to 0.1 M potassium phosphate dibasic solution (5 mL) and shaken for 10 min. After shaking, 0.5 mL of 6 N HCl and 5 mL of acetonitrile were added, and this solution was shaken for 10 min. Additionally, QuEChERS extraction salts (original method, 4 g MgSO4, 1 g NaCl) were added to the sample in a 50 mL conical tube. The mixture was strongly shaken for 1 min and centrifuged at 3000× g for 10 min. The acetonitrile layer was purified with dSPE (150 mg MgSO4, 25 mg C18) and was centrifuged at 13,000× g for 5 min. The supernatant was filtered with a membrane filter (pore size: 0.2 μm) before analysis. The ME (%, matrix effect) range for almost all analytes was −6.56 to 7.11%. MLOD (method limit of detection) and MLOQ (method limit of quantitative) values were calculated by the S/N ratio. MLOQs were 0.01 mg/kg. The linear correlation coefficients (R2) were >0.99 with the range of 0.5~25 μg/kg for all of the imidazolinone herbicides. The recoveries (of imidazolinone herbicides) were in the range of 76.1~110.6% (0.01 mg/kg level), 89.2~97.1% (0.1 mg/kg level), and 94.4~104.4% (0.5 mg/kg level). These are within the validation criteria (to recover 70–120% with RSD <20%). The method demonstrated the simple, rapid, high throughput screening and quantitative analysis of imidazolinone herbicide residues for monitoring in livestock products.