Herbicides Metolachlor Research Articles

Preparation and characterization of SPE column with smart green molecularly imprinted polymers materials for selective determination of S-metolachlor herbicide

The presence of traces of herbicides in ground and surface waters can have adverse impacts on humans and the environment. Therefore, developing a highly selective and reusable adsorbent for monitoring water quality has become important. This article describes smart green molecularly imprinted polymers (MIPs) as selective sorbents of S-metolachlor herbicide for solid phase extraction (SPE). Combining the MIP-SPE column with HPLC chromatography provided a quick and accurate method for determining the real concentration of S-metolachlor in water samples. The sorption capacity of the MIP-SPE column was almost twice that of the non-imprinted polymer column for SPE extraction. The bed can be regenerated up to three times before it loses its original sorption properties. A method has been developed whereby 6 ml of water can achieve an average recovery rate of 98% for sorbent. During the selectivity study from multicomponent solution, the calculate imprinting factor for MIPs was calculated to be 10, while MIPs sorb S-metolachlor 10 times better than atrazine, 12 times better than fenoxaprop-P-ethyl and 33 times better than glyphosate. The pseudo-second-order kinetic model was in good agreement with the experimental values obtained.

Optimized Metolachlor, Epoxiconazole and Chlorantraniliprole Mixture Analysis for Aquatic Toxicity Testing Using UHPLC-MS/MS.

The co-occurrence of pesticides in aquatic ecosystems highlights the need for studies investigating their potential toxicity as mixtures to the aquatic biota. Well-designed studies are essential to assess the presence and toxicity of relevant pesticide mixtures, particularly those such as the chloroacetamide herbicide metolachlor (MET), the triazole fungicide epoxiconazole (EP) and the diamide anthranilic insecticide chlorantraniliprole (CAP), which have not been previously tested, and whose co-occurrence is possible in waters close to cultivated areas. A solid phase extraction ultra-performance liquid chromatography-tandem quadrupole mass spectrometry method was developed to quantify equivalent toxicity concentrations for CAP, EP, and MET in artificial freshwater during acute toxicity tests. Compounds were separated within 1.30min, showing linearity over the calibration ranges of 2-150 µgL-1 for CAP and 50-3000 µgL-1 for EP and MET. Detection and quantification limits were (µgL-1): 0.001 and 0.0037 MET; 0.000038 and 0.00013 EP; and 0.002 and 0.007 CAP, respectively. Precision and accuracy met intra-assay validation requirements. Recoveries were tested at low and high concentration levels and were between 77% and 120%. Additionally, matrix effect showed different behavior among compounds. In an acute toxicity test proposed, MET and EP remained stable (24h), while CAP decayed 27% ± 4% in the same period. The method proved effective despite different concentrations in toxicity testing design.

Herbicidas pré-emergentes durante a entressafra do arroz irrigado para o controle de arroz-daninho e redução do banco de sementes

ABSTRACT: Weedy rice (Oryza sativa L.) is the most important weed in irrigated rice cultivation, being one of the main factors limiting cereal productivity in Rio Grande do Sul (RS). Thus, this study determined the effect of pre-emergent herbicide use in autumnal management on the control and reduction of the weedy rice seed bank. Field experiments were conducted in a randomized complete block design with four replications in a commercial rice production area in the 2021/22 and 2022/23 growing seasons in Dom Pedrito (RS). The scheme used was factorial, with factor A consisting of different herbicide application times, namely June, July, and August, and corresponding to 100, 78, and 26 days and 42, 26, and 10 days before rice sowing for the agricultural years 2021/22 and 2022/23, respectively. Factor B consisted of the application of the herbicides s-metolachlor (1440 g a.i. ha-1), sulfentrazone + diuron (210 and 420 g a.i. ha-1), piroxasulfone (170 g a.i. ha-1), and flumioxazin (50 g a.i. ha-1), in addition to the control (no application). The evaluated variables were control (%), number of plants (m-2) at crop pre-harvest, number of full, viable, and non-viable wild rice seeds m-2 in the soil, crop injury (%), and grain yield (kg ha-1). The herbicides showed control values below 25% and low reduction of the seed bank in the soil, being considered ineffective in this application modality. The herbicides s-metolachlor, sulfentrazone + diuron, and flumioxazin exhibited the highest injury values; however, they did not significantly affect crop productivity. Thus, when applied before rice sowing, the herbicides s-metolachlor, sulfentrazone + diuron, pyroxasulfone, and flumioxazin did not provided satisfactory control and do not significantly reduce the wild rice seed bank.

Assessing the Efficacy and Safety of Preemergence Herbicides Applied Alone or in Combination with Superabsorbent Polymer, Soil Binding Agent, and Compost in Tomato (Solanum lycopersicum L.) Plasticulture Production

Preemergence herbicide application under plastic mulch is an effective way to manage weeds in tomato (Solanum lycopersicum L.) production. Nonetheless, applying herbicides beneath plastic mulch in raised beds is associated with the inherent risk of crop phytotoxicity. This highlights the need to explore crop-safe methods for herbicide application in plastic mulch beds. The research aimed to evaluate the effectiveness of preemergence herbicides S-metolachlor and flumioxazin at the labeled rate (X) and reduced rate (0.5X, half of the labeled rate) either alone or in combination with a super absorbent polymer, soil binding agent, or compost to determine their ability to control weeds effectively in plastic mulched beds without causing negative effects on tomato crops. Two different experimental trials, trial 1 (Mar–Jun 2021) and trial 2 (Oct 2021–Jan 2022) were performed in the fields in Immokalee, FL, USA. The experimental design was a randomized complete block with five replications. S-metolachlor (X) plus soil binding agent and S-metolachlor (X) plus compost mix suppressed purple nutsedge density by >85% and approximately 68%, respectively, during trial II. Similarly, S-metolachlor (X), S-metolachlor (0.5X) plus super absorbent polymer, S-metolachlor (X) plus super absorbent polymer, S-metolachlor (X) plus soil binding agent, and S-metolachlor (X) plus compost caused reductions in purple nutsedge biomass by >50% compared with that of the nontreated control during trial II. Treatments did not significantly impact tomato crop vigor and chlorophyll contents during trials I and II. Moreover, treatments did not significantly affect tomato crop biomass and yield during both trials. In summary, using preemergence S-metolachlor (X) combined with soil binding agent or compost could be a viable option for suppressing purple nutsedge in plastic mulched tomato beds.

Field-evolved cross-resistance to ALS-inhibiting herbicides in redroot pigweed (Amaranthus retroflexus) populations and alternative chemical options for effective control

Abstract Twelve putative-resistant (R) redroot pigweed populations were collected in sunflower and soybean fields located in northeastern Greece, after repeated exposure to the acetolactate synthase (ALS)–inhibiting herbicides imazamox and tribenuron-methyl. Studies were conducted to determine the resistance status to these two ALS-inhibiting herbicides and evaluate alternative postemergence and preemergence herbicides for effective control. Two susceptible (S) populations were also included for comparison. Among the 12 putative-R populations studied in the whole-plant dose–response pot experiments, 11 were characterized as cross-resistant (R) to the imidazolinone imazamox and the sulfonylurea tribenuron-methyl. In contrast, the putative R5 and the two reference populations (S1, S2) populations were found to be susceptible. Sequencing of the ALS gene revealed that a point mutation (TGG to TTG at position 574) was selected in domain B, where in combination with domain A the majority of point mutations conferring resistance have been detected, resulting in an amino acid substitution from tryptophan (Trp) to leucine (Leu) in the 11 R populations. By contrast, all sequenced plants of the three susceptible populations were found with the wild-type allele encoding Trp574. The labeled rate of the postemergence herbicides tembotrione and dicamba provided fair to excellent control of the populations with ALS cross-resistance. In contrast, at this rate the preemergence herbicides S-metolachlor + terbuthylazine, isoxaflutole, aclonifen, metribuzin, and pendimethalin provided excellent control. These findings strongly suggest that 11 redroot pigweed populations have evolved cross-resistance to ALS-inhibiting herbicides, but viable options for chemical control of this weed still exist.

Management of resistant biotypes of Eleusine indica and glyphosate-tolerant Spermacocea latifolia with pre-emergent herbicides associated with sequential application of desiccants

It has been difficult to control Eleusine indica (L.) Gaertn and Spermacocea latifolia Aubl. in cotton and soybean crops due to their herbicide resistance or tolerance to glyphosate. Thus, this study's objective was to evaluate the herbicide efficacy applied in pre-emergence, associated with desiccant herbicide in sequential application, in these species. The experiments for S. latifolia and E. indica were conducted separately in a greenhouse. The experimental design was completely randomized, with 4 replications, in a 6 x 3 factorial. The first factor consisted of pre-emerging herbicides applied two days after the sowing of each species, diclosulam (35 g a.i./ha), s-metolachlor (600 g a.i./ha), pyroxasulfone (200 g a.i./ha) + flumioxazin (200 g a.i./ha), diuron (2000 g a.i./ha), trifluralin (600 g a.i./ha), and the treatment without herbicide. The second factor consisted of the application of diquat (200 g a.i./ha), ammonium glufosinate (400 g a.i./ha), or the absence of sequential application. The results revealed that only for the diclosulam herbicide a sequential application with desiccants was necessary for an effective control of E. indica. The other herbicide applied in pre-emergence showed high efficacy (> 90%) in E. indica control when applied individually. Regarding S. latifolia chemical control, the herbicides s-metolachlor (80.04%), pyroxasulfone + flumioxazin (100%), diclosulam (82.08%) and diuron (89.58%), applied in pre-emergence, presented a satisfactory control at 42 days after emergence. The sequential applications promoted better control of S. latifolia to trifluralin and diuron. In conclusion, there are pre-emergence options for the effective control of E. indica and S. latifolia. However, sequential application can be an important tool for improving the control of some weed species, such as those studied in this work, by certain herbicides.

Cultivo de soja em área de arroz irrigado para reduzir a infestação de plantas daninhas

ABSTRACT Lowland rice in Santa Catarina (SC), Brazil, is grown as a sole crop, which has aggravated problems with weeds. In this context, the objective of this study was to evaluate the efficacy of weed management systems in soybean crops to decrease weed infestation in lowland rice production areas, using pre- and post-emergence herbicides. The experiment was conducted in Turvo, SC, from August 2021 to April 2022. A randomized block design with four replications was used, in a 6 × 5 factorial arrangement. The factors consisted of six pre-emergence herbicides treatments (S-metolachlor, diclosulam, sulfentrazone, sulfentrazone + diuron, pyroxasulfone + flumioxazin, and a control without herbicide), and five post-emergence herbicide treatments: control without herbicide, glyphosate at two rates (930 and 1,550 g a.e. ha-1), applied alone or in combination with clethodim. The herbicide sulfentrazone caused persistent phytotoxicity and resulted in the lowest soybean grain yield. The herbicide S-metolachlor was ineffective in controlling weed species, except barnyard grass, even when combined with post-emergence application. The poor control of these weed species does not result in significant interference, causing no significant decreases in grain yield of soybean crops grown in floodplain soils. The use of S-metolachlor, diclosulam, and pyroxasulfone + flumioxazin, combined with post-emergence application of glyphosate (930 g a.e. ha-1), resulted in highly effective control of barnyard grass, inhibiting weed seed production. Only the combination of glyphosate (1,550 g a.e. ha-1) with clethodim can suppress barnyard grass seed production without using pre-emergence herbicides.

Compatibility Analysis of Metolachlor and Pendimethalin for Weed Control in Arabica Coffee Plants

Losses caused by the presence of weeds in an agricultural business are often associated with the ability of weeds as strong competitors for plants to obtain water, nutrients, sunlight, and growing space. A mixture of metolachlor and pendimethalin herbicides is expected to control important weeds of various classes in coffee plants. The purpose of the research was to determine the effect of two herbicide mixtures at different doses on weeds in coffee plantations. This research used a 4 X 4 factorial randomized block design with 2 repetitions, resulting in 32 experimental plots. The first factor was metolachlor herbicide and the second was pendimethalin herbicide, each factor consisting of 4 levels with 0.00, 0.75, 1.75 and 2.25 kg ha-1 doses. The observed parameters consisted of (1) dominance count value, (2) percentage of controlled weeds, (3) weed coverage, (4) weed population, and (5) weed dry weight. The results showed that there was a very significant effect on the combined interaction of metolachlor and pendimethalin herbicide mixtures on the percentage of controlled weeds, percentage of weed closure at 21 and 28 DAA, and weed dry weight at 28 and 42 DAA with the best dose combination at b.a. 1.50 kg ha-1 which could increase the efficiency of weed control. Meanwhile, the percentage of controlled weeds, percentage of weed cover at 14 DAA, and weed population at 28 and 42 DAA showed very significant results independently with a dose of b.a. 2.25 kg ha-1

Elucidating Factors Contributing to Dicamba Volatilization by Characterizing Chemical Speciation in Dried Dicamba-Amine Residues.

Dicamba is a semivolatile herbicide that has caused widespread unintentional damage to vegetation due to its volatilization from genetically engineered dicamba-tolerant crops. Strategies to reduce dicamba volatilization rely on the use of formulations containing amines, which deprotonate dicamba to generate a nonvolatile anion in aqueous solution. Dicamba volatilization in the field is also expected to occur after aqueous spray droplets dry to produce a residue; however, dicamba speciation in this phase is poorly understood. We applied Fourier transform infrared (FTIR) spectroscopy to evaluate dicamba protonation state in dried dicamba-amine residues. We first demonstrated that commercially relevant amines such as diglycolamine (DGA) and n,n-bis(3-aminopropyl)methylamine (BAPMA) fully deprotonated dicamba when applied at an equimolar molar ratio, while dimethylamine (DMA) allowed neutral dicamba to remain detectable, which corresponded to greater dicamba volatilization. Expanding the amines tested, we determined that dicamba speciation in the residues was unrelated to solution-phase amine pKa, but instead was affected by other amine characteristics (i.e., number of hydrogen bonding sites) that also correlated with greater dicamba volatilization. Finally, we characterized dicamba-amine residues containing an additional component (i.e., the herbicide S-metolachlor registered for use alongside dicamba) to investigate dicamba speciation in a more complex chemical environment encountered in field applications.

Enantioselectivity regulation of antibody against chiral herbicide metolachlor based on interaction at chiral center

Enantioselective antibodies have emerged as great potential biomaterials in the fields of immunoassays and chiral separation. However, cross-reactivity of antibodies to the distomer may severely restrict the application. Comprehending the interaction mechanism between antibodies and enantiomers could be beneficial to produce superior enantioselective antibodies. In this study, a pair of recombinant antibodies (RAbs) against metolachlor enantiomers at chiral carbon (αSS-MET and αSR-MET) were generated and characterized. The αSS-MET-RAb and αSR-MET-RAb showed comparable sensitivity and specificity to the parental monoclonal antibodies by icELISA, with IC50 values of 3.45 and 223.77 ng/mL, respectively. Moreover, the complex structures of RAbs and corresponding eutomer were constructed and analyzed, and site-specific mutagenesis was utilized to verify the reliability of the enantioselective mechanism elucidated. It demonstrated that the strength of the interaction between the chiral center region of eutomer and the antibody was the key factor for the enantioselectivity of antibody. Increasing this interaction could limit the conformational adjustment of the distomer in a specific chiral recognition cavity, thus decreasing the affinity of the antibody to the distomer. This work provided the in-depth analysis of enantioselective mechanism for two RAbs and paved the way to regulate antibody enantioselective performance for immunoassays of chiral compounds.

Changes in Soil Microbial Parameters after Herbicide Application in Soils under Conventional Tillage and Non-Tillage

This study evaluated the changes in microbial activity in the course of time following the joint application of the herbicides S-metolachlor, foramsulfuron, and thiencarbazone-methyl to two soils (S1 and S2) under conventional tillage (CT) and non-tillage (NT) management in field conditions. The biochemical parameters of soil respiration (RES), dehydrogenase activity (DHA), microbial biomass (BIO), and the phospholipid fatty acid (PLFA) profile were determined at 1, 34, and 153 days during herbicide dissipation. In the absence of herbicides, all microbial activity was higher under NT than CT conditions, with higher or similar mean values for S1 compared to S2. A continuous decrease was detected for RES, while DHA and BIO recovered over time. In the presence of herbicides, a greater decrease in all microbial activity was detected, although the changes followed a similar trend to the one recorded without herbicides. In general, a greater decrease was observed in S1 than in S2, possibly due to the higher adsorption and/or lower bioavailability of herbicides in this soil with a higher organic carbon content. The decrease was also greater under CT conditions than under NT conditions because the herbicides can be intercepted by the mulch, with less reaching the soil. These changes involved evolution of the structure of the microbial community.

Central Chirality and Axial Chirality Recognition of the Enantioselective Antibodies to Herbicide Metolachlor.

Enantioselective antibodies have emerged as efficient tools in the field of chiral chemical detection and separation. However, it is complicated to obtain a highly stereoselective antibody due to the unclear recognition mechanism. In this study, the hapten of metolachlor was synthesized and enantio-separated. The absolute configuration of the four haptens obtained was identified by the computed and experimental electronic circular dichroism comparison. Five polyclonal antibodies against the Rac-metolachlor and its enantiomers were generated by immunization. The cross-activity of all the 5 antibodies with 44 structural analogues, including metolachlor enantiomers, was tested. It demonstrated that antibodies have higher specificity to recognize central chirality than axial chirality. Especially, αRR-MET-Ab exhibited excellent specificity and stereoselectivity. Accordingly, 3D-QSAR models were constructed and revealed that paired stereoisomers exhibited opposite interactions with the antibodies. It is the first time that the antibodies against four stereoisomers were prepared and analyzed, which will be conducive to the rational design of the stereoselective antibodies.

Adsorption characteristics of S-Metolachlor onto the sawdust biochar derived from Acacia auriculiformis

The adsorption mechanism of S-Metolachlor in an aqueous solution by sawdust biochar derived from Acacia auriculiformis (SAB) was studied. SAB was manufactured at 500 °C for 4 h under oxygen-limited conditions and characterized for SEM, EDS, pHpzc, BET, and FTIR. The adsorption kinetics, isotherm, and diffusion studies of S-Metolachlor and SAB were further explored. Moreover, the effects of the solution pH were examined on the adsorption of S-Metolachlor by SAB. The BET analysis of SAB was achieved at 106.74 m2.g − 1 and the solution pH did not significantly influence the S-Metolachlor adsorption. The adsorption data were fitted into a Langmuir isotherm and the PSO model. The film diffusion coefficient Df (4.93 × 10 − 11 to 8.17 × 10 − 11 m2.s − 1) and the particle diffusion coefficient Dp (1.68 × 10 − 11 to 2.65 × 10 − 11 m2.s − 1) were determined and the rate-limiting step of S-Metolachlor adsorption and SAB was governed by liquid film diffusion. The S-Metolachlor adsorption process onto SAB was controlled by multiple mechanisms, including pore filling, H-bonding, hydrophobic interaction, and π-π EDA interactions. H-bonding is the main interaction for the adsorption of S-Metolachlor and SAB. Conclusively, the study illustrates that biochar produced from Acacia auriculiformis sawdust possessed effective adsorption properties for S-Metolachlor herbicide.

Widely used herbicide metolachlor can promote harmful bloom formation by stimulating cyanobacterial growth and driving detrimental effects on their chytrid parasites

Metolachlor (MET) is a widely used herbicide that can adversely affect phytoplanktonic non-target organisms, such as cyanobacteria. Chytrids are zoosporic fungi ubiquitous in aquatic environments that parasitize cyanobacteria and can keep their proliferation in check. However, the influence of organic pollutants on the interaction between species, including parasitism, and the associated ecological processes remain poorly understood. Using the host-parasite system consisting of the toxigenic cyanobacterium Planktothrix agardhii and its chytrid parasite Rhizophydium megarrhizum, we investigated the effects of environmentally relevant concentrations of MET on host-parasite interactions under i) continuous exposure of chytrids and cyanobacteria, and ii) pre-exposure of chytrids. During a continuous exposure, the infection prevalence and intensity were not affected, but chytrid reproductive structures were smaller at the highest tested MET concentration. In the parasite's absence, MET promoted cyanobacteria growth possibly due to a hormesis effect. In the pre-exposure assay, MET caused multi- and transgenerational detrimental effects on parasite fitness. Chytrids pre-exposed to MET showed reduced infectivity, intensity, and prevalence of the infection, and their sporangia size was reduced. Thus, pre-exposure of the parasite to MET resulted in a delayed decline of the cyanobacterial cultures upon infection. After several parasite generations without MET exposure, the parasite recovered its initial fitness, indicating that detrimental effects are transient. This study demonstrates that widely used herbicides, such as MET, could favor cyanobacterial bloom formation both directly, by promoting cyanobacteria growth, and indirectly, by inhibiting their chytrid parasites, which are known to play a key role as top-down regulators of cyanobacteria. In addition, we evidence the relevance of addressing multi-organism systems, such as host-parasite interactions, in toxicity assays. This approach offers a more comprehensive understanding of the effects of pollutants on aquatic ecosystems.

Effects of metolachlor and fish cues on tadpole antipredator behaviors

Antipredator behaviors are often crucial for animal survival. In environments impacted by humans, animals may be exposed to a wide array of chemical contaminants due to agriculture, industry, and other activities. Among other effects, these chemical contaminants may influence behaviors prey animals use to cope with predation risk, likely reducing survival by suppressing or even maladaptively reversing normal behavioral responses. Changes in behavioral responses could be the result of impaired detection of cues that indicate predator presence or altered behavioral plasticity in response to predator cues. In a laboratory experiment, we tested the effects of the commonly used herbicide metolachlor on the behavior of tadpoles of the American bullfrog (Lithobates catesbeianus) in both the absence and presence of water conditioned with cues (odor) of fish. We observed several behaviors in the tadpoles reflective of predator avoidance when exposed to combinations of metolachlor (0 or 80 ppb) and the presence or absence of fish cues. We found that metolachlor had size-dependent effects on tadpole activity levels, with larger tadpoles being much less active in the absence of metolachlor but similar in activity to small tadpoles when metolachlor was present. Fish cues similarly had size-dependent effects on multiple tadpole behaviors. Finally, hiding behavior and zone change (movement) behavior of tadpoles in response to fish cues varied depending on the presence of metolachlor and, in the case of zone changes, tadpole size. Our findings indicate that the presence of chemical contaminants has the potential to alter important antipredator behaviors. However, these effects are complex, and size may mediate the nature of the response to both chemical contaminants and predators.

Impact of soil-residual herbicides on industrial hemp (Cannabis sativa) phytotoxicity and biomass yield in west Texas

Abstract Industrial hemp is a multipurpose crop cultivated for fiber, seed, human food, and animal feed. Hemp legalization in Texas creates a considerable potential to increase its acreage in semi-arid conditions; however, knowledge is limited on growing hemp optimally in Texas. Best management practices, including weed control, require evaluation for profitable hemp production. As little is known about the herbicide tolerance of hemp, field studies were conducted to test several soil-residual herbicides with different modes of action for phytotoxicity to two hemp cultivars, ‘Yuma’ and ‘Jinma’. The experimental units were randomized three times in a blocked split-plot design with hemp cultivars in the main plots and soil-residual herbicides in the subplots. Ethalfluralin, the mixture of sulfentrazone and S-metolachlor, prometryn, and S-metolachlor, resulted in 60% to 90% and 73% to 100% weed control as compared to the nontreated control in 2021 and 2022, respectively. The highest hemp germination, stand count, and plant height were observed with ethalfluralin and S-metolachlor herbicides; however, no significant differences were observed for hemp germination and plant height compared to the nontreated control. S-metolachlor, ethalfluralin, fomesafen, and prometryn resulted in similar hemp biomass compared to the nontreated control. Overall, the results indicate that hemp is tolerant to ethalfluralin, prometryn, and S-metolachlor, and these soil-residual herbicides were effective for weed control in hemp. The mixture of bicyclopyrone plus S-metolachlor, metribuzin plus S-metolachlor, and mesotrione should be avoided, as they caused significant injury to hemp plants. Future research is needed to test the efficacy of different preemergence and postemergence herbicides that can be used in industrial hemp grown under different environments, making sure the delta-9-tetrahydrocannabinol content of the hemp is below the legal content restrictions.

γ-Glutamylation of Isopropylamine by Fermentation.

Glutamylation yields N-functionalized amino acids in several natural pathways. γ-Glutamylated amino acids may exhibit improved properties for their industrial application, e. g., as taste enhancers or in peptide drugs. γ-Glutamyl-isopropylamide (GIPA) can be synthesized from isopropylamine (IPA) and l-glutamate. In Pseudomonas sp. strain KIE171, GIPA is an intermediate in the biosynthesis of l-alaninol (2-amino-1-propanol), a precursor of the fluorochinolone antibiotic levofloxacin and of the chloroacetanilide herbicide metolachlor. In this study, fermentative production of GIPA with metabolically engineered Pseudomonas putida KT2440 using γ-glutamylmethylamide synthetase (GMAS) from Methylorubrum extorquens was established. Upon addition of IPA during growth with glycerol as carbon source in shake flasks, the recombinant strain produced up to 21.8 mM GIPA. In fed-batch bioreactor cultivations, GIPA accumulated to a titer of 11 g L-1 with a product yield of 0.11 g g-1 glycerol and a volumetric productivity of 0.24 g L-1 h-1 . To the best of our knowledge, this is the first fermentative production of GIPA.

Tolerance of Brazilian Bean Cultivars to S-Metolachlor and Poaceae Weed Control in Two Agricultural Soils

Brazil stands out in the world for being one of the largest producers and consumers of common beans and cowpeas. However, the cultivation of this agricultural species is exposed to competition with weeds for water, light and nutrients. One of the management methods for weed control is the use of pre-emergent herbicides. Although pre-emergence herbicides are beneficial in controlling weeds, it is important to know the dynamics of these products in the soil, especially their residual effect. Two experiments were carried out to assess the tolerance of bean genotypes to the pre-emergent herbicide S-metolachlor in two Brazilian soils. Bean genotypes have differential tolerance to S-metolachlor when grown in soils with different characteristics. The Vigna spp. were the most affected by S-metolachlor, especially the red Adzuki. Plant growth was more sensitive when grown in sandy soil for most species. Total chlorophyll content was not affected for most genotypes in the two soils evaluated. The differential tolerance of the genotypes in both soils confirms the potential of S-metolachlor to cause damage to the bean crop, especially in sandy soil. The S-metolachlor was efficient in controlling sourgrass and selective to the bean cultivars (Pérola and Talismã) in both soils evaluated. Alexandergrass behaved differently in the soils evaluated, showing tolerance to the application of S-metolachlor when in Oxisol and sensitivity in Ultisol.

Integrating transcriptome and physiological analyses to elucidate the molecular responses of sorghum to fluxofenim and metolachlor herbicide

The extensive use of herbicides has raised concerns about crop damage, necessitating the development of effective herbicide safeners. Fluxofenim has emerged as a promising herbicide safener; however, it's underlying mechanism remains unclear. Here, we screened two inbred lines 407B and HYZ to investigate the detoxication of fluxofenim in mitigating metolachlor damage in sorghum. Metolachlor inhibited seedling growth in both 407B and HYZ, while, fluxofenim could significantly restore the growth of 407B, but not effectively complement the growth of HYZ. Fluxofenim significantly increased the activities of glutathione-S-transferase (GST) to decrease metolachlor residue in 407B, but not in HYZ. This implys that fluxofenim may reduce metolachlor toxicity by regulating its metabolism. Furthermore, metolachlor suppressed AUX-related and JA-related genes expression, while up-regulated the expression of SA-related genes. Fluxofenim also restored the expression of AUX-related and JA-related genes inhibited by metolachlor and further increased expression of SA-related genes. Moreover, we noted a significant increase in the content of trans-zeatin O-glucoside (tZOG) and Gibberellin1 (GA1) after the fluxofenim treatment. In conclusion, fluxofenim may reduce the injury of herbicide by affecting herbicide metabolism and regulating hormone signaling pathway.

Palmelloid-like phenotype in the alga Raphidocelis subcapitata exposed to pollutants: A generalized adaptive strategy to stress or a specific cellular response?

This work focuses on the formation of palmelloid-like phenotype in the freshwater alga Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata and Selenastrum capricornutum), when exposed to adverse conditions generated by the presence of organic [the antibiotic erythromycin (ERY) and the herbicide metolachlor (MET)] or inorganic [the heavy metals, cadmium (Cd) and zinc (Zn)] pollutants, at environmentally relevant concentrations. This alga in absence of stress or when exposed to ERY or Zn, up to 200 µg/L, essentially showed a single-nucleus state, although algal growth was reduced or stopped. R. subcapitata “switched” to a multinucleated state (palmelloid-like morphology) and accumulated energy-reserve compounds (neutral lipids) when stressed by 100–200 µg/L MET or 200 µg/L Cd; at these concentrations of pollutants, growth was arrested, however, the majority of the algal population (≥83 %) was alive. The formation of palmelloid-like phenotype, at sub-lethal concentrations of pollutants, was dependent on the pollutant, its concentration and exposure time. The multinucleated structure is a transitory phenotype since R. subcapitata population was able to revert to a single-nucleus state, with normal cell size, within 24–96 h (depending on the impact of the toxic in the alga), after being transferred to fresh OECD medium, without pollutants. The obtained results indicate that the formation of a palmelloid-like phenotype in R. subcapitata is dependent on the mode of action of toxics and their concentration, not constituting a generalized defense mechanism against stress. The observations here shown contribute to understanding the different strategies used by the unicellular alga R. subcapitata to cope with severe stress imposed by organic and inorganic pollutants.