Glyphosate Selection Research Articles

Determination of glyphosate using electrochemical aptamer-based label-free voltammetric biosensing platform

Glyphosate is currently the most frequently used herbicide in the agricultural industry. Due to its widespread usage, there are concerns about its potential toxicity when it contaminates water, soil, and agricultural products. In this study, a simple aptamer-based biosensor was developed to detect glyphosate. The electrode surfaces were modified by reducing diazonium salts during electrodeposition and forming carboxylic acid groups. The immobilization of aminoated glyphosate aptamers on the electrode surface was then carried out using a carbodiimide reaction between the amino and carboxylic acid groups. The electrochemical cell circuit was completed using an analyte and redox probe solution on the electrode surface. Cyclic voltammetry, differential pulse, and electrochemical impedance spectroscopy techniques were then explored to investigate their potential as biosensors. Upon exposure to glyphosate, the spatial conformation of the specific aptamer used is altered, which generates an electrochemical response that can be quantified. Glyphosate could be quantified using voltammetry in the 1 to 5000 nM range, with a 0.67 nM detection limit. Furthermore, the constructed aptasensor demonstrated significant selectivity for glyphosate in the presence of interfering substances like glycine, dimethoate, and alanine. This biosensor has considerable potential for evaluating glyphosate in actual samples because of its simple design, high sensitivity, and rapid functionality. Moreover, developing a simple, cost-effective, and portable device for field applications may be possible.

Artificial evolution of OsEPSPS through an improved dual cytosine and adenine base editor generated a novel allele conferring rice glyphosate tolerance.

Exploiting novel endogenous glyphosate-tolerant alleles is highly desirable and has promising potential for weed control in rice breeding. Here, through fusions of different effective cytosine and adenine deaminases with nCas9-NG, we engineered an effective surrogate two-component composite base editing system, STCBE-2, with improved C-to-T and A-to-G base editing efficiency and expanded the editing window. Furthermore, we targeted a rice endogenous OsEPSPS gene for artificial evolution through STCBE-2-mediated near-saturated mutagenesis. After hygromycin and glyphosate selection, we identified a novel OsEPSPS allele with an Asp-213-Asn (D213N) mutation (OsEPSPS-D213N) in the predicted glyphosate-binding domain, which conferred rice plants reliable glyphosate tolerance and had not been reported or applied in rice breeding. Collectively, we developed a novel dual base editor which will be valuable for artificial evolution of important genes in crops. And the novel glyphosate-tolerant rice germplasm generated in this study will benefit weeds management in rice paddy fields.

Sensitive fluorescence assay for the detection of glyphosate with NAC[sbnd]Cu2+ complex

Glyphosate is widely used as an herbicide in weed control. However, the excessive use and residue of glyphosate adversely affect the environment. Thus, a rapid and highly sensitive system must be developed for glyphosate detection. Herein, a novel turn-on fluorescent probe was designed and synthesized for glyphosate, that is N-butyl-1,8-naphthalimide-4-hydrazino-6-isopropyl-chromone (NAC). The fluorescence of NAC was quenched by the addition of Cu2+ to form NACCu2+ complex in dimethyl sulfoxide/2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (DMSO/HEPES, 9/1, v/v, pH = 7.0). Upon the addition of glyphosate, the fluorescence of NACCu2+ was recovered through chelation between Cu2+ and glyphosate. The NACCu2+ complex exhibited the desired linearity of glyphosate concentration under optimum conditions in the range of 0–40 μM with a low detection limit of 36 nM. Based on competitive coordination, NACCu2+ exhibited good sensitivity and selectivity for glyphosate. Moreover, NAC was successfully utilized to detect glyphosate in tap water, local water from Songhua River, soil, maize, and soybean with convenient operations, indicating a promising application in pesticide residue detection.

Herbicide selectivity on teak seedlings (Tectona grandis L.f)

The experiment was installed at the IFAL campus Maceió, in Maceió, Alagoas, with the objective of evaluating the selectivity of saflufenacil and glyphosate in teak seedlings from seeds, through morphological, physiological and visual analysis. With Entirely Random Blocks (DBC) with five repetitions; the treatments were: Saflufenacil (100 gha-1 of active ingredient), Glyphosate (1000 gha-1 ia), association of Saflufenacil and Glyphosate (100 gha-1 ia + 1000 gha-1 ia) and the control (the control without application of herbicides). The results obtained allow us to conclude that there is selectivity between the treatments observed in the evaluation period.

Agronomic Performance of RR® Soybean Submitted to Glyphosate Application Associated with a Product Based on Bacillus subtilis

Despite the great benefits arising from the adoption of Roundup Ready® (RR®) soybean, there are reports about the lack of selectivity of glyphosate for this crop. The use of growth-promoting microorganisms can help attenuate the injuries caused by herbicides. The objective of this work was to evaluate the agronomic performance of RR® soybean submitted to the post-emergence application of glyphosate both isolated and in association with Bacillus subtilis. The experiment was carried out in a completely randomized block design, with four replications. The treatments consisted of the post-emergence applications of glyphosate (1296 g a.i. ha−1), glyphosate (2592 g a.i. ha−1), glyphosate/glyphosate (1296/1296 g a.i. ha−1), glyphosate + B. subtilis BV02 (1296 + 42 g a.i. ha−1), glyphosate + B. subtilis BV02 (2592 + 42 g a.i. ha−1), and glyphosate + B. subtilis BV02/glyphosate + B. subtilis BV02 (1296 + 42/1296 + 42 g a.i. ha−1). The application of glyphosate (2592 g a.i. ha−1) and the sequential application of glyphosate provides higher levels of intoxication. The association of B. subtilis BV02 with glyphosate (2592 g a.i. ha−1) prevented losses in the values of relative chlorophyll a and b and the total chlorophyll index. The soybean yield was reduced when the plants were submitted to a sequential application of glyphosate.

Two novel enzyme-free colorimetric sensors for the detection of glyphosate in real samples

The intensive use and accumulation of glyphosate cause many environmental and ecological problems. There is an urgent need for an effective detection method for glyphosate. Many studies in the literature determine glyphosate by an enzyme-based method, requiring appropriate temperature, pH, substrate and ionic strength. In this study, we presented a simple enzyme-free reaction system. Two new simple Schiff base derivatives, 4-(((3-chloropyridin-4-yl)imino)methyl)-N,N-dimethylaniline (BNP-Cl) and 4-((3-((3-chloropyridin-4-yl)imino)propenyl)-N,N-dimethylaniline (CNP-Cl), were prepared by combining a pyridine moiety with a cinnamaldehyde or a benzaldehyde moiety. The pyridine moiety contains a chlorine atom, and this chlorine atom is replaced by the nitrogen or oxygen of glyphosate (Glyp) in ACN/Tris buffer (pH=8.14, 10 mM, v/v 2:1). This binding caused color changes ranging from colorless to yellow for BNP-Cl and yellow to orange for CNP-Cl. The sensors BNP-Cl and CNP-Cl have a rapid and excellent selectivity for glyphosate with low detection limits (1.78 µM for BNP-Cl and 1.60 µM for CNP-Cl). The sensors were also successfully applied to detect Glyp in real samples such as soil, tap water, and potatoes.

The Naturally Evolved EPSPS From Goosegrass Confers High Glyphosate Resistance to Rice.

Glyphosate-resistant crops developed by the CP4-EPSPS gene from Agrobacterium have been planted on a massive scale globally, which benefits from the high efficiency and broad spectrum of glyphosate in weed control. Some glyphosate-resistant (GR) genes from microbes have been reported, which might raise biosafety concerns. Most of them were obtained through a hygromycin-HPT transformation system. Here we reported the plant source with 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene from goosegrass endowed rice with high resistance to glyphosate. The integrations and inheritability of the transgenes in the rice genome were investigated within two generations. The EiEPSPS transgenic plants displayed similar growth and development to wild type under no glyphosate selection pressure but better reproductive performance under lower glyphosate selection pressure. Furthermore, we reconstructed a binary vector pCEiEPSPS and established the whole stage glyphosate selection using the vector. The Glyphosate-pCEiEPSPS selection system showed a significantly higher transformation efficiency compared with the hygromycin-HPT transformation system. Our results provided a promising alternative gene resource to the development of GR plants and also extended the plant transformation toolbox.

New Fluorescent Probes for the Sensitive Determination of Glyphosate in Food and Environmental Samples.

In this paper, a dual-functional probe, 2-(benzothiazol)-4-(3-hydroxy-4-methylphenyl) imino phenol (BHMH), was synthesized and characterized for the simultaneous detection of Cu2+ and Fe3+ in dimethyl sulfoxide/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (DMSO/HEPES) (1:4, v/v, pH = 6.0). The limits of detections (LODs) for Cu2+ and Fe3+ were 9.05 and 48 nM, respectively. Based on the competitive coordination, the complex BHMH-Cu2+/Fe3+ exhibited good sensitivity and selectivity for glyphosate. The LODs of BHMH-Cu2+ and BHMH-Fe3+ for glyphosate were 0.41 and 0.63 μM, respectively. The probe quantitatively detected glyphosate in tap water, Songhua River water, local water and soil, and food samples. The colorimetric on-site glyphosate sensing through the probe BHMH-Cu2+ was also studied based on smartphones. BHMH and BHMH-Cu2+/Fe3+ exhibited outstanding imaging capabilities for Cu2+, Fe3+, and glyphosate in living cells with low cytotoxicity, especially the first time for glyphosate.

A reaction-based system for the colorimetric detection of glyphosate in real samples

Glyphosate is widely used herbicides and causes several diseases in humans. Therefore, the detection of glyphosate is curial and urgent. Studies on the detection of glyphosate in literature are often based on inhibition of the enzyme acetylcholinesterase. In this study, we developed two simple colorimetric sensors, BP-Cl and CP-Cl, by linking 3-chloro-4-methylpyridine with 4-(dimethylamino)cinnamaldehyde or 4-(dimethylamino)benzaldehyde in a one-step reaction. The colorimetric and optical sensing properties of these compounds were investigated by the naked-eye and UV–Vis spectrophotometer in ACN/HEPES buffer (5 mM pH 8.0, 1:1 v/v). The sensors displayed high sensitivity and selectivity for glyphosate by color changes, which ranged from colorless to yellow for BP-Cl and yellow to orange for CP-Cl. The detection limits of BP-Cl and CP-Cl by the naked-eye detection were found as 15 µM and 10 µM. On the other hand, the detection limits of BP-Cl and CP-Cl via UV–Vis measurements were calculated as 0.847 µM and 1.23 µM, respectively. Moreover, the sensors were able to monitor glyphosate in water samples using the naked-eye, UV–Vis spectroscopy, and filter paper strips.

Effect of EPSPS gene copy number and glyphosate selection on fitness of glyphosate-resistant Bassia scoparia in the field

The widespread evolution of glyphosate-resistant (GR) Bassia scoparia in the U.S. Great Plains poses a serious threat to the long-term sustainability of GR sugar beet. Glyphosate resistance in B. scoparia is due to an increase in the EPSPS (5-enolpyruvyl-shikimate-3-phosphate) gene copy number. The variation in EPSPS gene copies among individuals from within a single GR B. scoparia population indicated a differential response to glyphosate selection. With the continued use of glyphosate in GR sugar beet, the effect of increasing glyphosate rates (applied as single or sequential applications) on the fitness of GR B. scoparia individuals with variable EPSPS gene copies was tested under field conditions. The variation in EPSPS gene copy number and total glyphosate rate (single or sequential applications) did not influence any of the reproductive traits of GR B. scoparia, except seed production. Sequential applications of glyphosate with a total rate of 2214 g ae ha−1 or higher prevented seed production in B. scoparia plants with 2–4 (low levels of resistance) and 5–6 (moderate levels of resistance) EPSPS gene copies. Timely sequential applications of glyphosate (full recommended rates) can potentially slow down the evolution of GR B. scoparia with low to moderate levels of resistance (2–6 EPSPS gene copies), but any survivors (highly-resistant individuals with ≥ 8 EPSPS gene copies) need to be mechanically removed before flowering from GR sugar beet fields. This research warrants the need to adopt ecologically based, multi-tactic strategies to reduce exposure of B. scoparia to glyphosate in GR sugar beet.

A basic scheme of soybean transformation for glyphosate tolerance using Agrobacterium tumefaciens through an approximation of patents: a review

Concern has been expressed on the control of agricultural biotechnology through patents that may adversely affect the development of competing crops. Soybean is one of the most important crops around the world (~287 million t per year), above potatoes (45 million t per year), tomatoes (23 million t per year), or wheat (116 million t per year), with prices for American producers ranging between USD 278.8 and USD 650.3 t-1. Soybean belongs to the Fabaceae family and has been genetically modified (GM) to improve its tolerance to herbicides, including glyphosate, its resistance to insect pests, and the quality of soy oil. Glyphosate-tolerant soybean has received a gene coding for the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). There are a number of variables that contribute to the development of a GM soybean event. Such variables include tissue culture, selection methods, cloning vectors, and Agrobacterium strains that affect transformation efficiency and can be associated with patents. Chlorine gas disinfection is the most appropriate technique for plant material. Production of explants with shoots and molecular and phenotypic features (e.g., antibiotic susceptibility) of bacterial strain must be assessed. A long-term glyphosate selection arrangement is the most suitable and a consistent approach for the selection of events of GM soybean with tolerance to glyphosate. Freedom-to-operate evaluation must be carried out to find the specific elements neccesary for GM plant development that do not infringe the rights of third parties. These rights come into effect from the patent application date for a definite geographical region involving construct design and its synthesis, transformation vector, bacterial strain, methods, or reporter gene. In this review, the protocols relating to experiments for the development of GM soybean using an epsps gene are included, and considerations relating to intellectual property rights are involved. The major elements associated with each stage of the development of patents are described including the following: the soybean genotype, seed disinfection, genetic construct design and its synthesis, tissue culture protocols, selection strategy without gene reporter, and Agrobacterium strain. This review is a guide for carrying out technical procedures when the desired product is the off-patent GM soybean with tolerance to glyphosate.

An ABCC-type transporter endowing glyphosate resistance in plants

Glyphosate is the most widely used herbicide in world agriculture and for general vegetation control in a wide range of situations. Global and often intensive glyphosate selection of very large weedy plant populations has resulted in widespread glyphosate resistance evolution in populations of many weed species. Here, working with a glyphosate-resistant (GR) Echinochloa colona population that evolved in a Western Australia agricultural field, we identified an ATP-binding cassette (ABC) transporter (EcABCC8) that is consistently up-regulated in GR plants. When expressed in transgenic rice, this EcABCC8 transporter endowed glyphosate resistance. Equally, rice, maize, and soybean overexpressing the EcABCC8 ortholog genes were made resistant to glyphosate. Conversely, CRISPR/Cas9-mediated knockout of the EcABCC8 ortholog gene OsABCC8 increased rice susceptibility to glyphosate. Subcellular localization analysis and quantification of glyphosate cellular levels in treated ABCC8 transgenic rice plants and isolated leaf protoplasts as well as structural modeling support that EcABCC8 is likely a plasma membrane-localized transporter extruding cytoplasmic glyphosate to the apoplast, lowering the cellular glyphosate level. This is a report of a membrane transporter effluxing glyphosate in a GR plant species, and its function is likely conserved in crop plant species.

Stability of EPSPS gene copy number in Hordeum glaucum Steud (barley grass) in the presence and absence of glyphosate selection.

Gene amplification has been shown to provide resistance to glyphosate in several weed species, including Hordeum glaucum populations in South Australia. The stability of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copies in resistant populations in the presence or absence of glyphosate selection has not been determined. Applying glyphosate to a cloned plant resulted in an increase in resistance and EPSPS copy number in the progeny of that plant compared to the untreated clone. The LD50 (herbicide concentration required for 50% mortality) increased by 75% to 79% in the progeny of the treated clones compared to the untreated in both populations (YP-17 and YP-16). EPSPS copy number estimates were higher in treated individuals compared to untreated individuals with an average of seven copies compared to six in YP-16 and 11 compared to six in YP-17. There was a positive correlation (R2 =0.78) between EPSPS copy number and LD50 of all populations. EPSPS gene copy number and resistance to glyphosate increased in H. glaucum populations under glyphosate selection, suggesting the number of EPSPS gene copies present is dependent on glyphosate selection. © 2021 Society of Chemical Industry.

Contrasting plant ecological benefits endowed by naturally occurring EPSPS resistance mutations under glyphosate selection.

Concurrent natural evolution of glyphosate resistance single‐ and double‐point EPSPS mutations in weed species provides an opportunity for the estimation of resistance fitness benefits and prediction of equilibrium resistance frequencies in environments under glyphosate selection. Assessment of glyphosate resistance benefit was conducted for the most commonly identified single Pro‐106‐Ser and less‐frequent double TIPS mutations in the EPSPS gene evolved in the global damaging weed Eleusine indica. Under glyphosate selection at the field dose, plants with the single Pro‐106‐Ser mutation at homozygous state (P106S‐rr) showed reduced survival and compromised vegetative growth and fecundity compared with TIPS plants. Whereas both homozygous (TIPS‐RR) and compound heterozygous (TIPS‐Rr) plants with the double TIPS resistance mutation displayed similar survival rates when exposed to glyphosate, a significantly higher fecundity in the currency of seed number was observed in TIPS‐Rr than TIPS‐RR plants. The highest plant fitness benefit was associated with the heterozygous TIPS‐Rr mutation, whereas plants with the homozygous Pro‐106‐Ser and TIPS mutations exhibited, respectively, 31% and 39% of the fitness benefit revealed by the TIPS‐Rr plants. Populations are predicted to reach stable allelic and genotypic frequencies after 20 years of glyphosate selection at which the WT allele is lost and the stable genotypic polymorphism is comprised by 2% of heterozygous TIPS‐Rr, 52% of homozygous TIPS‐RR and 46% of homozygous P106S‐rr. The high inbreeding nature of E. indica is responsible for the expected frequency decrease in the fittest TIPS‐Rr in favour of the homozygous TIPS‐RR and P106S‐rr. Mutated alleles associated with the glyphosate resistance EPSPS single EPSPS Pro‐106‐Ser and double TIPS mutations confer contrasting fitness benefits to E. indica under glyphosate treatment and therefore are expected to exhibit contrasting evolution rates in cropping systems under recurrent glyphosate selection.

Herbicides in agronomic performance and chlorophyll indices of Enlist E3 and Roundup Ready soybean

Soybean DAS-44406-6 (Enlist E3) is tolerant to glyphosate, 2,4-D and glufosinate. However, more information is needed on selectivity of 2,4-D choline on Enlist E3 soybean, alone or in mixtures. The aim of this study was to evaluate herbicide effects on agronomic performance and chlorophyll indices of soybean. Glyphosate was applied at different stages of development of Enlist E3 and RR soybean. Furthermore, 2,4-D choline alone and in mixture with glyphosate or glufosinate were also applied on Enlist E3 soybean. Studies were conducted in 2016/17 and 2017/18 seasons. Experiment 1 consisted of application of glyphosate. The treatments were arranged in a 2x4 factorial (genotpes x growth stage). For genotypes, Enlist E3 and RR were used. For growth stage, control (without application), V4, V6 and R2 were used. Experiment 2 consisted of application of 2,4-D choline, glyphosate, glufosinate and associations, at V4 of Enlist E3 soybean. Crop injury, chlorophyll indices and agronomic performance were evaluated. The equivalent selectivity of glyphosate for Enlist E3 and RR soybean was verified, regardless of the stage. 2,4-D choline, alone or in mixtures, did not reduce chlorophyll indices and yield of Enlist E3 soybean after application at V4. Enlist E3 soybean was found to be tolerant to 2,4-D choline, glyphosate and glufosinate. The results showed that, in addition to glyphosate, Enlist E3 soybean may be an alternative for glyphosate resistant weeds

Chitosan-Based Nanocomposites for Glyphosate Detection Using Surface Plasmon Resonance Sensor.

This article describes an optical method based on the association of surface plasmon resonance (SPR) with chitosan (CS) film and its nanocomposites, including zinc oxide (ZnO) or graphene oxide (GO) for glyphosate detection. CS and CS/ZnO or CS/GO thin films were deposited on an Au chip using the spin coating technique. The characterization, morphology, and composition of these films were performed by Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle technique. Sensor preparation conditions including the cross-linking and mobile phase (pH and salinity) were investigated and thoroughly optimized. Results showed that the CS/ZnO thin-film composite provides the highest sensitivity for glyphosate sensing with a low detection limit of 8 nM and with high reproducibility. From the Langmuir-type adsorption model and the effect of ionic strength, the adsorption mechanisms of glyphosate could be controlled by electrostatic and steric interaction with possible formation of 1:1 outer-sphere surface complexes. The selectivity of the optical method was investigated with respect to the sorption of glyphosate metabolite (aminomethylphosphonic acid) (AMPA), glufosinate, and one of the glufonisate metabolites (3-methyl-phosphinico-propionic acid) (MPPA). Results showed that the SPR sensor offers a very good selectivity for glyphosate, but the competition of other molecules could still occur in aqueous systems.

Glyphosate selection of maize transformants containing CP4epsps gene

Aim. To study the selection conditions of maize transformants containing the CP4epsps gene using glyphosate as a selective agent. Methods. Tissue culture in vitro, Agrobacterium-mediated transformation, selection of transgenic plants, isolation of total plant DNA, analysis of plant DNA by polymerase chain reaction (PCR). Results. The morphogenic maize callus of immature embryos of the hybrid (PLS61)R2×PLS61 was produced, which had a high regeneration rate (up to 95%), that persisted over long cultivation. Agrobacterium mediated transformation of the morphogenic callus and selection of the transgenic material using glyphosate yielded maize transformants containing the CP4epsps gene at a frequency of 1%. Conclusions. Maize genotype (PLS61)R2×PLS61 is promising for studies on the maize genetic transformation, in particular for the production of transgenic maize resistant to glyphosate herbicide. The use of morphogenic maize callus (PLS61)R2×PLS61 and glyphosate as a selective agent at a concentration of 0.1 mM and 0.25 mM in media for callusogenesis and 0.01 mM in the medium for regeneration was effective for the selection of transgenic plants with the gene CP4epsps.
 Keywords: Zea mays L., morphogenic callus, Agrobacterium-mediated transformation, PCR, genetic engineering.

Glyphosate resistance in Eleusine indica: EPSPS overexpression and P106A mutation evolved in the same individuals

Goosegrass is one of the most widespread weeds in orchards and tea plantations in China, and glyphosate is a popular herbicide used to control it. However, high glyphosate selection pressure has led to some populations becoming resistant. The objectives of this research were to determine resistance levels and possible resistance mechanisms of goosegrass populations from several tea plantations in Zhejiang Province in China. The resistance indexes in four goosegrass populations (SH, SY, CA and CX) ranged from 4.9 to 13.4, and lower shikimate accumulation in these populations compared with a glyphosate-susceptible (GS) population confirmed their resistance to glyphosate. No mutations in the target gene EPSPS were found in populations SH and SY, however, the expression of EPSPS in these two populations was 9.3 and 29.7 times higher than that in the GS population, respectively. In the CX population, a P106S mutation in EPSPS was found in 6.7% of the individuals and another 80.0% of individuals had EPSPS amplification. In population CA, all the individuals had a P106A mutation and 86.7% of them had amplification in EPSPS. The EPSPS copy numbers ranged from 5.2 to 62.3 in these four resistant populations. There was a positive correlation between signal intensities of primary anti-EPSPS antibody and the copy number of the EPSPS protein, as indicated by immunoblot analysis. In population CA, with high-level resistance to glyphosate, both P106A mutation and amplification in EPSPS evolved in the same individuals in this population.

Performance of RR soybean submitted to postemergence application of glyphosate with a foliar elicitor product

ABSTRACT With the advent of glyphosate-resistant soybean, postemergence applications of the herbicide have become routine. In this way, problems related to the selectivity of glyphosate have been shown to be increasingly intense, due to the use of increased dosages and applications of the herbicide at unrecommended moments. In order to evaluate the agronomic performance of soybean plants subjected to the postemergence application of glyphosate – both in isolation and together with Crop+ – at different stages and dosage levels, a randomized block design experiment was carried out with two adjacent checks and four repetitions. The treatments consisted of: glyphosate (1296 g·ha-1); glyphosate + Crop+ (1296 + 0.25 g or L·ha-1); glyphosate + Crop+ (1296 + 0.5 g or L·ha-1); glyphosate (2592 g·ha-1); glyphosate + Crop+ (2592 + 0.25 g or L·ha-1); glyphosate + Crop+ (2592 + 0.5 g or L·ha-1); 2 × glyphosate (2 × 1296 g·ha-1); 2 × glyphosate + Crop+ (2 × 1296 + 0.25 g or L·ha-1); 2 × glyphosate + Crop+ (2 × 1296 + 0.5 g or L·ha-1) and Crop+ (0.5 g·ha-1). The phytotoxicity, soil plant analysis development (SPAD) index, height, stand, mass of 100 grains, and yield of the soybean plants were evaluated. The use of Crop+ on soybean plants led to an increase in the SPAD index; the use of Crop+ in association with glyphosate made possible the attenuation of visible symptoms of damage, preventing reductions in crop yield.

Evolutionary epidemiology predicts the emergence of glyphosate resistance in a major agricultural weed.

The evolution of resistance to herbicides is a striking example of rapid, human-directed adaptation with major consequences for food production. Most studies of herbicide resistance are performed reactively and focus on post hoc determination of resistance mechanisms following the evolution of field resistance. If the evolution of resistance can be anticipated, however, pro-active management to slow or prevent resistance traits evolving can be advocated. We report a national-scale study that combines population monitoring, glyphosate sensitivity assays, quantitative genetics and epidemiological analyses to pro-actively identify the prerequisites for adaptive evolution (directional selection and heritable genetic variation) to the world's most widely used herbicide (glyphosate) in a major, economically damaging weed species, Alopecurus myosuroides. Results highlighted pronounced, heritable variability in glyphosate sensitivity amongst UK A.myosuroides populations. We demonstrated a direct epidemiological link between historical glyphosate selection and current population-level sensitivity, and show that current field populations respond to further glyphosate selection. This study provides a novel, pro-active assessment of adaptive potential for herbicide resistance, and provides compelling evidence of directional selection for glyphosate insensitivity in advance of reports of field resistance. The epidemiological approach developed can provide a basis for further pro-active study of resistance evolution across pesticide resistance disciplines.