High pressure Raman spectra and DFT calculation of glyphosate

Glyphosate, N-(phosphonomethyl)glycine, (C₃H₈NO₅P), was obtained through the method of slow evaporation method from aqueous solution and its structure analyzed through X-ray diffraction and the Rietveld method. The normal modes of the crystal were investigated using Raman spectroscopy and Density Functional Theory to obtain the assignment of most of the normal modes in the spectral range between 3070 and 45 cm^-1. The crystal was compressed to high pressure through a diamond anvil cell, up to 6.2 GPa. From the behavior of the modes corresponding to both internal modes and lattice modes it was possible to discovery two phase transitions undergone by glyphosate, one between 0.97 and 1.5 GPa and other in the pressure interval 4.29-4.63 GPa. The analysis of the Raman spectra also indicates a certain disorder and conformational changes of the molecules in the unit cell at high pressure. Additionally, the phase transitions revealed to be reversible, with no cracking of the sample in the compression - decompression run.

Design, Synthesis, and Molecular Mechanism Studies of N-Phenylisoxazoline-thiadiazolo[3,4-a]pyridazine Hybrids as Protoporphyrinogen IX Oxidase Inhibitors

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) is an important target for green agrochemical discovery. Herein, a novel N-phenylisoxazoline-thiadiazolo[3,4-a]pyridazine herbicidal active scaffold was designed by the scaffold hybridization strategy. Systematic structural optimization enabled the discovery of a series of derivatives with excellent weed control at 9.375-150 g ai/ha by the post-emergent application. Some derivatives exhibited improved Nicotiana tabacum PPO (NtPPO)-inhibitory activity than fluthiacet-methyl. Of these, 2b, with K_i = 21.8 nM, displayed higher weed control than fluthiacet-methyl at the rate of 12-75 g ai/ha, and selective to maize at 75 g ai/ha. In planta, 2b was converted into a bioactive metabolite 5 (K_i = 4.6 nM), which exhibited 4.6-fold more potency than 2b in inhibiting the activity of NtPPO. Molecular dynamics simulation explained that 5 formed stronger π-π interaction with Phe392 than that of 2b. This work not only provides a promising lead compound for weed control in maize fields but is also helpful to understand the molecular mechanism and basis of the designed hybrids.

High Value-Added Use of Citrus Industrial Wastes in Agriculture: Semisynthesis and Anti-Tobacco Mosaic Virus/Insecticidal Activities of Ester Derivatives of Limonin Modified in the B Ring

Globally, the citrus industry produces various wastes, which contain a great deal of limonoids. In order for the sustainable development of the citrus industry, and considering the diverse bioactivities of limonoids, a series of ester derivatives were constructed by structural modification of limonin in the B ring. Furthermore, two seven-membered lactone derivatives of limonin and obacunone with a novel skeleton in the B ring were obtained by the Baeyer-Villiger oxidation rearrangement. The steric structures of six key compounds 3a, 3b, 4m, 4n, 6, and 7 were determined by X-ray crystallography. It demonstrated that the molar ratio of 3a (7α-isomer) and 3b (7β-isomer) depended on the mixed solvents in the reduction system. The anti-tobacco mosaic virus (TMV) activities under three different modes of action for most of the tested compounds were as the following sequence: inactivation effect > protection effect > curative effect. It was noteworthy that compound 4aa displayed the most potent anti-TMV/insect growth inhibitory activities, which indicated that the introduction of the phenylacryloyloxy group at the C-7β position of limonin could significantly improve its agricultural biological activities. This study will pave the way for future value-added application of citrus industrial wastes and provide strong evidence for the discovery of sustainable biopesticides based on limonoids.

Tandem Photoredox Catalysis: Enabling Carbonylative Amidation of Aryl and Alkylhalides

We report a new visible-light-mediated carbonylative amidation of aryl, heteroaryl, and alkyl halides. A tandem catalytic cycle of [Ir(ppy)₂ (dtb-bpy)]⁺ generates a potent iridium photoreductant through a second catalytic cycle in the presence of DIPEA, which productively engages aryl bromides, iodides, and even chlorides as well as primary, secondary, and tertiary alkyl iodides. The versatile in situ generated catalyst is compatible with aliphatic and aromatic amines, shows high functional-group tolerance, and enables the late-stage amidation of complex natural products.

Herbicidal and Antifungal Xanthone Derivatives from the Alga-Derived Fungus Aspergillus versicolor D5

Fungi have been proved as promising and prolific sources of functional secondary metabolites with potent agricultural applications. In this study, 14 xanthone derivatives (1-14), including six new ones, versicones I-N (1-4, 7, 11), and a biogenetically related derivative (15), were isolated from the alga-derived fungus Aspergillus versicolor D5. Their structures were elucidated by comprehensive spectroscopic methods. Versicone L (4) exhibited a broad antifungal spectrum and prominent inhibitory effects on Botrytis cinerea at a minimum inhibitory concentration (MIC) of 152 μM, 7-fold stronger than that of the positive control, carbendazim (MIC = 1.05 × 10³ μM). Dihydrosterigmatocystin (13) showed strong antifungal activity toward B. cinerea at MIC = 38.3 μM, almost 30-fold stronger than that of carbendazim. Meanwhile, 13 exhibited potent herbicidal activity toward Amaranthus retroflexus L. with an MIC of 24.5 μM, approximately 4-fold stronger than that of the positive control, glyphosate (MIC = 94.7 μM). Additionally, 13 also displayed remarkable activity against other weeds belonging to Amaranth sp. Analysis of the structure-herbicidal activity relationship indicated that the bifuranic ring played an important role in xanthone phytotoxicity and the presence of a double bond in the furan ring could decrease phytotoxicity. This study indicated that xanthones can be served as promising candidates for lead compounds of agrochemicals.

Review on Structures of Pesticide Targets

Molecular targets play important roles in agrochemical discovery. Numerous pesticides target the key proteins in pathogens, insect, or plants. Investigating ligand-binding pockets and/or active sites in the proteins' structures is usually the first step in designing new green pesticides. Thus, molecular target structures are extremely important for the discovery and development of such pesticides. In this manuscript, we present a review of the molecular target structures, including those of antiviral, fungicidal, bactericidal, insecticidal, herbicidal, and plant growth-regulator targets, currently used in agrochemical research. The data will be helpful in pesticide design and the discovery of new green pesticides.

Synthesis and Biological Evaluation of Novel Benodanil-Heterocyclic Carboxamide Hybrids as a Potential Succinate Dehydrogenase Inhibitors

In order to discover new antifungal agents, twenty novel benodanil-heterocyclic carboxamide hybrids were designed, synthesized, and characterized by ¹H NMR and HRMS. In vitro, their antifungal activities against four phytopathogenic fungi were evaluated, as well as some of the target compounds at 50 mg/L demonstrated significant antifungal activities against Rhizoctonia solani. Especially, compounds 17 (EC₅₀ = 6.32 mg/L) and 18 (EC₅₀ = 6.06 mg/L) exhibited good antifungal activities against R. solani and were superior to the lead fungicide benodanil (a succinate dehydrogenase inhibitor, SDHI) (EC₅₀ = 6.38 mg/L). Furthermore, scanning electron microscopy images showed that the mycelia on treated media with the addition of compound 17 grew abnormally as compared with the negative control with tenuous, wizened, and overlapping colonies, and compounds 17 (IC₅₀ = 52.58 mg/L) and 18 (IC₅₀ = 56.86 mg/L) showed better inhibition abilities against succinate dehydrogenase (SDH) than benodanil (IC₅₀ = 62.02 mg/L). Molecular docking revealed that compound 17 fit in the gap composed of subunit B, C, and D of SDH. Furthermore, it was shown that the main interaction, one hydrogen bond interaction, was observed between compound 17 and the residue C/Trp-73. These studies suggested that compound 17 could act as a potential fungicide to be used for further optimization.

New reduced-risk agricultural nematicides - rationale and review

The last decade has seen a sharp increase in nematicide research in the agricultural industry. As a result, several new synthetic nematicides have become available to growers, and several more are expected in the near future. This new interest in nematicides is directly related to the growing demand for safer and more selective products, and the increasing regulatory pressure on many of the traditional nematicides. This has led to a ban of several widely used fumigant (e.g. methyl bromide) and non-fumigant (e.g. aldicarb) nematicides. The loss of traditional nematicides, combined with a lack of replacement products and awareness of the damage that nematodes can cause, has not only raised concern among growers, but has also created new opportunities for the crop protection industry. Nematicides have become a priority, and many companies are now allocating significant research dollars to discover new nematicides. The new nematicides are very different from previous products: (i) they are more selective, often only targeting nematodes, and (ii) they are less toxic, and safer to use. This review article describes these new developments by discussing the challenges that are associated with finding new nematicides, reviewing the nature, characteristics, and efficacy of new nematicides, and discussing the impact they could have on future nematode management.

The potential use of the Penicillium chrysogenum antifungal protein PAF, the designed variant PAFopt and its γ-core peptide Pγopt in plant protection

The prevention of enormous crop losses caused by pesticide-resistant fungi is a serious challenge in agriculture. Application of alternative fungicides, such as antifungal proteins and peptides, provides a promising basis to overcome this problem; however, their direct use in fields suffers limitations, such as high cost of production, low stability, narrow antifungal spectrum and toxicity on plant or mammalian cells. Recently, we demonstrated that a Penicillium chrysogenum-based expression system provides a feasible tool for economic production of P. chrysogenum antifungal protein (PAF) and a rational designed variant (PAFopt ), in which the evolutionary conserved γ-core motif was modified to increase antifungal activity. In the present study, we report for the first time that γ-core modulation influences the antifungal spectrum and efficacy of PAF against important plant pathogenic ascomycetes, and the synthetic γ-core peptide Pγopt , a derivative of PAFopt , is antifungal active against these pathogens in vitro. Finally, we proved the protective potential of PAF against Botrytis cinerea infection in tomato plant leaves. The lack of any toxic effects on mammalian cells and plant seedlings, as well as the high tolerance to harsh environmental conditions and proteolytic degradation further strengthen our concept for applicability of these proteins and peptide in agriculture.

Harnessing microbial volatiles to replace pesticides and fertilizers

Global agricultural systems are under increasing pressure to deliver sufficient, healthy food for a growing population. Seasonal inputs, including synthetic pesticides and fertilizers, are applied to crops to reduce losses by pathogens, and enhance crop biomass, although their production and application can also incur several economic and environmental penalties. New solutions are therefore urgently required to enhance crop yield whilst reducing dependence on these seasonal inputs. Volatile Organic Compounds (VOCs) produced by soil microorganisms may provide alternative, sustainable solutions, due to their ability to inhibit plant pathogens, induce plant resistance against pathogens and enhance plant growth promotion. This review will highlight recent advances in our understanding of the biological activities of microbial VOCs (mVOCs), providing perspectives on research required to develop them into viable alternatives to current unsustainable seasonal inputs. This can identify potential new avenues for mVOC research and stimulate discussion across the academic community and agri-business sector.

A knowledge-based approach to designing control strategies for agricultural pests

Chemical control of insect pests remains vital to agricultural productivity, but limited mechanistic understanding of the interactions between crop, pest and chemical control agent have restricted our capacity to respond to challenges such as the emergence of resistance and demands for tighter environmental regulation. Formulating effective control strategies that integrate chemical and non-chemical management for soil-dwelling pests is particularly problematic owing to the complexity of the soil-root-pest system and the variability that occurs between sites and between seasons. Here, we present a new concept, termed COMPASS, that integrates ecological knowledge on pest development and behaviour together with crop physiology and mechanistic understanding of chemical distribution and toxic action within the rhizosphere. The concept is tested using a two-dimensional systems model (COMPASS-Rootworm) that simulates root damage in maize from the corn rootworm Diabrotica spp. We evaluate COMPASS-Rootworm using 119 field trials that investigated the efficacy of insecticidal products and placement strategies at four sites in the USA over a period of ten years. Simulated root damage is consistent with measurements for 109 field trials. Moreover, we disentangle factors influencing root damage and pest control, including pest pressure, weather, insecticide distribution, and temporality between the emergence of crop roots and pests. The model can inform integrated pest management, optimize pest control strategies to reduce environmental burdens from pesticides, and improve the efficiency of insecticide development.

Insecticides, biologics and nematicides: Updates to IRAC's mode of action classification - a tool for resistance management

Insecticide resistance has been and continues to be a significant problem for invertebrate pest control. As such, effective insecticide resistance management (IRM) is critical to maintain the efficacy of current and future insecticides. A technical group within CropLife International, the Insecticide Resistance Action Committee (IRAC) was established 35 years ago (1984) as an international association of crop protection companies that today spans the globe. IRAC's focus is on preserving the long-term utility of insect, mite, and most recently nematode control products through effective resistance management to promote sustainable agriculture and improved public health. A central task of IRAC has been the continual development and documentation of the Mode of Action (MoA) Classification scheme, which serves as an important tool for implementing IRM strategies focused on compound rotation / alternations. Updates to the IRAC MoA Classification scheme provide the latest information on the MoA of current and new insecticides and acaricides, and now includes information on biologics and nematicides. Details for these new changes and additions are reviewed herein.

A simple and effective strategy to enhance the stability and solid-liquid interfacial interaction of an emulsion by the interfacial dilational rheological properties

The development of an emulsion is an important challenge in many fields, such as agrochemicals, pharmaceutics, paints, cosmetics, inkjet printing, and food science. However, the traditional strategies that refer to the empirical value and complex secondary additives cannot reflect the influence of the structure, content, compound, and adsorption of emulsifiers. Here, we propose a simple and effective strategy to develop the emulsion, wherein the emulsifiers are chosen based on the dilational rheological properties of the interfacial films at the molecular level. The dilational rheological properties of polyoxyethylene (80) castor oil (EL-80), sorbitan monostearate (Span 60), and their emulsions were explored by the oscillating drop method. Based on the dilational rheological properties, the emulsions were prepared by the phase inversion emulsification technique. The results showed that the emulsion was stable and realized effective solid-liquid interfacial interaction, which was attributed to the large dilational modulus (intermolecular interaction) at the oil/water interface and loss modulus (molecular diffusion exchange) at the air/water interface. These factors reduced the Ostwald ripening and coalescence, and finally increased the spreading diameter. Additionally, the prochloraz 25% emulsion in water (EW) and difenoconazole 20% EW were developed to verify the feasibility of the strategy. Therefore, this research advances the understanding of an emulsion by interfacial dilational rheological properties, which can provide a simple and effective strategy to develop a stable emulsion and achieve an effective solid-liquid interfacial interaction of the emulsion.

Unprecedented Quassinoids from Eurycoma longifolia: Biogenetic Evidence and Antifeedant Effects

Six new quassinoids (1-6) were isolated from the roots of Eurycoma longifolia, and their structures with absolute configurations were determined unambiguously by spectroscopic analyses and single-crystal X-ray crystallographic experiments. Compounds 1 and 2 are the first members of a new class of quassinoids with an unusual C₂₆ carbon skeleton. Compound 6 features a C₂₀ cage-like scaffold with an unprecedented densely functionalized 2,5-dioxatricyclo[5.2.2.0^4,8]undecane core. The discovery of the two C₂₆ quassinoids 1 and 2 has provided firm evidence for the better understanding the biogenetic process from C₃₀ triterpenoid precursors to quassinoids. Compound 5 exhibited significant antifeedant activity on the diamondback moth (DBM) larvae and excellent systemic absorption and accumulated properties in Brassica chinensis.

Carbonic Anhydrase Sensitivity to Pesticides: Perspectives for Biomarker Development

Carbonic anhydrase (CA) is a widespread metalloenzyme playing a pivotal role in several physiological processes. Many studies have demonstrated the in vitro and in vivo sensitivity of CA to the exposure to several classes of pesticides in both humans and wildlife. This review aims to analyze and to discuss the literature available in this field, providing a comprehensive view useful to foresee perspectives for the development of novel CA-based pesticide biomarkers. The analysis of the available data highlighted the ability of several pesticide molecules to interact directly with the enzyme in humans and wildlife and to inhibit CA activity in vitro and in vivo, with possible alterations of key physiological functions. The analysis disclosed key areas of further research and, at the same time, identified some perspectives for the development of novel CA-based sensitive biomarkers to pesticide exposure, suitable to be used in several fields from human biomonitoring in occupational and environmental medicine to environmental monitoring on non-target species.

Novel insecticidal chitinase from the insect pathogen Xenorhabdus nematophila

Xenorhabdus nematophila strain ATCC 19061 is an insect pathogen that produces various protein toxins which intoxicate and kill its larval host. In the present study, we have described the cloning, expression and characterization of a 76-kDa chitinase protein of X. nematophila. A 1.9 kb DNA sequence encoding the chitinase gene was PCR amplified and cloned. Further, the chitinase protein was expressed in Escherichia coli and purified by using affinity chromatography. Two highly conserved domains were identified GH18 and ChiA. The purified chitinase protein showed chitobiosidase activity, β-N-acetylglucosaminidase and endochitinase activity, when enzyme activity was measured using respective substrates. The purified chitinase protein was found to be orally toxic to the larvae of a major crop pest, Helicoverpa armigera when fed to the larvae mixed with artificial diet. It also had adverse effect on the growth and development of the surviving larvae. Surviving larvae showed 9-fold reduction in weight, as a result the transformation of larvae into pupae was adversely affected. Our results demonstrated that the chitinase protein of X. nematophila has insecticidal property and can prove to be a potent candidate for pest control in plants.

Intellectual property in entomology: Analysis and perspective on recent trends in global patent publications

Intellectual property (IP) is an important consideration for entomological research and provides a means to capture value from new discoveries. Herein, we describe an analysis of more than 26 000 patent publications from 2007-2017 related to the field of entomology. These patents were divided among 8000 patent assignees; however, only 5% of the assignees had ≥10 patents. Corporations accounted for the largest share of patents (59%), with individuals (20%), academic institutions (17%) and government organizations (4%) making up the remaining segments. From 2007-2017 the number of entomological patents increased by 400%, with the largest number being from China. However, unlike patents from Europe, Japan or the US, which target a range of countries, the Chinese patents almost exclusively focus on China. Among the array of subjects covered are transgenic insects and plants, repellents, recombinant insect cells, with the highest proportion of patents focused on insecticides (39%), followed by insecticide mixtures (27%) and formulations (21%). The top 30 patent assignees included companies/institutions from China (18), Europe (3), Japan (6) and the US (3). Among the top 12 entities, IP from the US assignees was distributed across insecticides, mixtures and insecticidal traits while those from China were more focused on mixtures. However, given expanding IP numbers from China it is expected that in the future there will be a greater impact on new insecticides and related technologies. © 2020 Society of Chemical Industry.

Cellulose Nanocrystals Loaded with Thiamethoxam: Fabrication, Characterization, and Evaluation of Insecticidal Activity against Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

Using smart nanopesticide formulations based on nanomaterials can offer promising potential applications for decreasing pesticide residues and their effects on human health and the environment. In this study, a novel nanoformulation (NF) of thiamethoxam (TMX) was fabricated using the solvent evaporation method through loading TMX on cellulose nanocrystals (CNCs) as the carrier. The synthesized TMX-CNCs was investigated through different techniques, such as Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and thermogravimetric analysis (TGA). The results revealed that the loading efficiency and entrapment efficiency were 18.7% and 83.7 ± 1.8% for TMX, respectively. The prepared nanoformulation (TMX-CNCs) had a width of 7-14 nm and a length of 85-214 nm with a zeta potential of -23.6 ± 0.3 mV. The drug release behavior study exhibited that the release of TMX from TMX-loaded CNCs was good and sustained. Furthermore, bioassay results showed that the insecticidal activity of TMX-CNCs against Phenacoccus solenopsis was significantly superior to that of the technical and commercial formulation, as indicated by the lower LC₅₀ value. The results indicate that the TMX nanoformulation has great potential for application in agriculture for pest control.

Nanocarriers for the Delivery of Medical, Veterinary, and Agricultural Active Ingredients

Nanocarrier-based delivery systems can be used to increase the safety and efficacy of active ingredients in medical, veterinary, or agricultural applications, particularly when such ingredients are unstable, sparingly soluble, or cause off-target effects. In this review, we highlight the diversity of nanocarrier materials and their key advantages compared to free active ingredients. We discuss current trends based on peer-reviewed research articles, patent applications, clinical trials, and the nanocarrier formulations already approved by regulatory bodies. Although most nanocarriers have been engineered to combat cancer, the number of formulations developed for other purposes is growing rapidly, especially those for the treatment of infectious diseases and parasites affecting humans, livestock, and companion animals. The regulation and prohibition of many pesticides have also fueled research to develop targeted pesticide delivery systems based on nanocarriers, which maximize efficacy while minimizing the environmental impact of agrochemicals.

Thermodynamics and Kinetics of Pretilachlor Adsorption on Organobentonites for Controlled Release

Thermodynamics and kinetics of pretilachlor adsorption on organobentonites modified with hexadecyltrimethyl ammonium chloride were investigated to reveal the structural effects of organobentonites on the interaction with pretilachlor and the diffusion of the herbicide and were related to the controlled release from organobentonites. The adsorption of pretilachlor was entropically driven by hydrophobic interaction. The entropy change dropped with increasing surfactant loading from 0.4 to 1.50 times the cation exchange capacity (CEC) of the bentonite used, corresponding to a decrease in the degree of freedom of pretilachlor molecules due to the enhanced order of surfactant in the interlayer. The kinetics of pretilachlor adsorption was well fitted to the pseudo-second-order model and related to the structural features of organobentonites. The enhanced packing density of the surfactant in the interlayer generally resulted in a reduction of the rate constant of the pretilachlor adsorption onto organobentonites. However, the stepwise increase in the basal spacing due to the surfactant arrangement transition, from lateral-monolayer to lateral-bilayer at a loading level of more than 0.8 × CEC, benefited the diffusion of pretilachlor and diminished the influence of the increase in surfactant packing density. The release of pretilachlor from organobentonites was predominated by Fickian diffusion, which could be understood from the adsorption thermodynamics and kinetics. The time taken for the release of 50% of active ingredient was 16-23 times that for the control formulation and exhibited a linear increase with the relative value of the equilibrium constant to the rate constant of pretilachlor adsorption.

Synthesis of Sulfamate-Fused 2-Aminopyrroles via an Isocyanide-Based Three Component [1+2+2] Annulation

An efficient preparation of sulfamate-fused 2-aminopyrroles was achieved through an isocyanide-based three-component [1+2+2] annulation of isocyanides, dialkyl acetylenedicarboxylates, and sulfamate-derived cyclic imines in good to excellent yields (up to 99 %). This reaction proceeds smoothly without any activation or modification of substances under neutral and metal-free conditions. The reaction could also be conveniently performed on a gram scale.

Discovery of novel insecticidal 3-aminopyridyl ureas

BACKGROUND

Commercial compound databases represent rich sources of potential starting points for pharmaceutical and agrochemical product development. Routine insecticidal screening of compounds ordered from these sources led to the identification of a 3-aminopyridyl urea with activity against Myzus persicae (Sulzer) (green peach aphid). Based on this activity and its structural novelty, further exploration of the chemical space around this hit was initiated.

RESULTS

A series of ureas based on the structure of the initial hit were synthesized and screened for insecticidal activity. A broad range of tail groups derived from cyclic secondary amines were explored, and many of these compounds were found to be insecticidally active. However, only compounds featuring a 3-aminopyridine or 4-aminopyridazine head group exhibited significant insecticidal potency. Although activity against M. persicae was consistently observed, these ureas were largely inactive against another key sap-feeding insect pest, Bemisia tabaci (Glennadius) (sweetpotato whitefly).

CONCLUSIONS

Follow-up of an insecticide hit identified from commercial compound acquisition led to the discovery of a novel class of ureas with activity against M. persicae. Despite considerable effort to identify related compounds with additional insecticidal spectrum, however, activity on other important pests remains limited. © 2019 Society of Chemical Industry.

Difunctional Fluorescence Nanoparticles for Accurate Tracing of Nanopesticide Fate and Crop Protection Prepared by Flash Nanoprecipitation

Facile fabrication of difunctional nanoparticles (NPs) for pesticide delivery and imaging is still a fascinating challenge. Here, water-dispersible difunctional NPs were developed using flash nanoprecipitation (FNP) where self-assembling amphiphilic block copolymers were used to encapsulate a highly hydrophobic model pesticide, Lambda-cyhalothrin, and the fluorescent dye Nile red. The particle size (ranging from 158 to 280 nm) and fluorescence property of NPs could be controlled by varying the flow rate or Nile red feed concentration. The aggregation state and rearrangement of the dye molecules in the NPs were also investigated. IVIS imaging and confocal laser scanning microscopy analysis demonstrated that the resulting difunctional nanopesticide particles could allow accurate in situ tracking of the pesticide on the leaf surface, while effectively avoiding interference from chlorophyll autofluorescence. The difunctional NP suspension maintained high insecticidal activity and stability. This work demonstrates the feasibility and great potential of the FNP method in universal fabrication of multifunctional NPs with in situ pesticide tracing and crop protection capabilities.

An innovative automated active compound screening system allows high-throughput optimization of somatic embryogenesis in Coffea arabica

Somatic embryogenesis (SE) faces many challenges in fulfilling the growing demand for elite materials. A high-throughput approach is required to accelerate the optimization of SE protocols by multiplying experimental conditions within a limited time period. For the first time in plant micropropagation, we have developed a miniaturized and automated screening system to meet high-throughput standards. Coffea arabica embryo regeneration, classically achieved in 250-ml Erlenmeyer flasks, was successfully miniaturized in 24-well plates, allowing a volume downscaling factor of 100 and a space saving of 53 cm²/well. Cell clusters were ground and filtered to fit the automated pipetting platform, leading to fast, reproducible and uniform cluster distribution (23.0 ± 5.5 cell clusters/well) and successful regeneration (6.5 ± 2.2 embryos/well). Pilot screening of active compounds on SE was carried out. Compounds belonging to the histone deacetylase inhibitor family were tested for embryo regeneration efficiency. Cells treated with 1 µM Trichostatin A showed a marked 3-fold increase in the number of regenerated embryos. When re-tested in 250-ml flasks, the same enhancement was obtained, thereby validating the miniaturized and automated screening method. These results showed that our screening system is reliable and well suited to screening hundreds of compounds, offering unprecedented perspectives in plant micropropagation.

Nanotechnology as a new sustainable approach for controlling crop diseases and increasing agricultural production

Climate change will negatively affect crop production by exacerbating the incidence of disease and decreasing the efficacy of conventional approaches to disease control. Nanotechnology is a promising new strategy for plant disease management that has many advantages over conventional products and approaches, such as better efficacy, reduced input requirements, and lower eco-toxicity. Studies on crop plants using various nanomaterials (NMs) as protective agents have produced promising results. This review focuses on the use of NMs in disease management through three different mechanisms: (i) as antimicrobial agents; (ii) as biostimulants that induce plant innate immunity; and (iii) as carriers for active ingredients such as pesticides, micronutrients, and elicitors. The potential benefits of nanotechnology are considered, together with the role that NMs might play in future disease management and crop adaptation measures.

A dispensable paralog of succinate dehydrogenase subunit C mediates standing resistance towards a subclass of SDHI fungicides in Zymoseptoria tritici

Succinate dehydrogenase inhibitor (SDHI) fungicides are widely used for the control of a broad range of fungal diseases. This has been the most rapidly expanding fungicide group in terms of new molecules discovered and introduced for agricultural use over the past fifteen years. A particular pattern of differential sensitivity (resistance) to the stretched heterocycle amide SDHIs (SHA-SDHIs), a subclass of chemically-related SDHIs, was observed in naïve Zymoseptoria tritici populations not previously exposed to these chemicals. Subclass-specific resistance was confirmed at the enzyme level but did not correlate with the genotypes of the succinate dehydrogenase (SDH) encoding genes. Mapping and characterization of the molecular mechanisms responsible for standing SHA-SDHI resistance in natural field isolates identified a gene paralog of SDHC, termed ZtSDHC3, which encodes for an alternative C subunit of succinate dehydrogenase, named alt-SDHC. Using reverse genetics, we showed that alt-SDHC associates with the three other SDH subunits, leading to a fully functional enzyme and that a unique Qp-site residue within the alt-SDHC protein confers SHA-SDHI resistance. Enzymatic assays, computational modelling and docking simulations for the two SQR enzymes (altC-SQR, WT_SQR) enabled us to describe enzyme-inhibitor interactions at an atomistic level and to propose rational explanations for differential potency and resistance across SHA-SDHIs. European Z. tritici populations displayed a presence (20–30%) / absence polymorphism of ZtSDHC3, as well as differences in ZtSDHC3 expression levels and splicing efficiency. These polymorphisms have a strong impact on SHA-SDHI resistance phenotypes. Characterization of the ZtSDHC3 promoter in European Z. tritici populations suggests that transposon insertions are associated with the strongest resistance phenotypes. These results establish that a dispensable paralogous gene determines SHA-SDHIs fungicide resistance in natural populations of Z. tritici. This study paves the way to an increased awareness of the role of fungicidal target paralogs in resistance to fungicides and demonstrates the paramount importance of population genomics in fungicide discovery.

Zymoseptoria tritici is the causal agent of Septoria tritici leaf blotch (STB) of wheat, the most devastating disease for cereal production in Europe. Multiple succinate dehydrogenase inhibitor (SDHI) fungicides have been developed and introduced for the control of STB. We report the discovery and detailed characterization of a paralog of the C subunit of the SDH enzyme conferring standing resistance towards the SHA-SDHIs, a particular chemical subclass of the SDHIs. The SDHC paralog is characterized by its presence/absence, expression and alternative splicing polymorphisms, which in turn influence resistance levels. The identified mechanisms exemplify the importance of population genomics for the discovery and rational design of the most adapted solutions.

Semisynthesis and biological evaluation of some novel Mannich base derivatives derived from a natural lignan obovatol as potential antifungal agents

Obovatol, a novel lignan isolated from the leaf and stem bark of Magnolia obovata Thunb exhibits many important biological activities. To discover natural-product-based potential fungicides with novel structural skeletons, a series of Mannich base derivatives were prepared by the C-4-aminomethylated modification of obovatol and all synthesized compounds were evaluated for antifungal activities in vitro against several phytopathogenic fungi using the spore germination method and the mycelium growth rate method. Furthermore, their structures were also characterized by ¹H NMR, ¹³C NMR, and HR-MS, and compound 2k was further analyzed by single-crystal X-ray diffraction. Among all of the derivatives, compounds 2b (IC₅₀ = 28.68 µg/mL) and 2g (IC₅₀ = 16.90 µg/mL) demonstrated greater inhibition of Botrytis cinerea spore germination than two positive controls, hymexazol and difenoconazole. Compounds 2c, 2f, and 2g displayed potent mycelial growth inhibition of B. cinerea with an average inhibition rate (AIR) of >90% at a concentration of 100 µg/mL. Additionally, the structure-activity relationships (SARs) suggested that the introduction of a diethylamino, pyrrolyl, 1-methyl-piperazinyl or 1-ethyl-piperazinyl groups on the C-4 position of obovatol may be more likely to yield potential antifungal compounds than the introduction of 4-phenyl-piperazinyl or 4-phenyl-piperidinyl groups.

The larvicidal activity of natural inspired piperine-based dienehydrazides against Culex pipiens

A series of piperine-based dienehydrazide derivatives were designed and synthesized to be used as insecticides against Culex pipiens. The chemical structure of compound 5n was confirmed by single-crystal x-ray diffraction. Their insecticidal activities of synthesized compounds were tested against third-instar larval of Cx. pipiens at concentrations ranging from 0.1 to 1.2 mg/mL. Among all derivatives, compounds 5a, 5b, 5f, 5g, 5m, 5n, 5o, 5p, and 5u displayed good activities. The final mortality rates at the concentration of 0.75 mg/mL after 48 h treatment, were found to be in the range from 80.00 to 83.33% and with LC₅₀ values ranging from 0.221 to 0.094 mg/mL. These compounds demonstrated higher insecticidal activities than piperine and Deltamethrin (a commercial positive control). Molecular modelling reveals several molecular interactions between synthesized compounds and the substrate binding sits of acetylcholinesterase (AChE) that are predicted to be responsible for its binding and inhibition activity. .

Perspectives on new strategies for the identification and development of insecticide targets

The discovery and development of new active ingredients to control arthropod populations and circumvent the inevitable evolution of insecticide resistance has been of consistent interest to the field of insecticide science. This interest has resulted in a slow, but steady increase in the diversity of chemical scaffolds and biochemical target sites within the insecticide arsenal over the past 70 years with growth from three biochemical target sites in the 1950s to 22 distinct biochemical targets in 2018. Despite this growth, the number of biochemical target sites for insecticides remains relatively limited when compared to human pharmaceuticals, which has approximately 700 distinct biochemical targets that are targeted by FDA approved drugs. Potential reasons for this large discrepancy between two closely related fields and putative mechanisms to enhance the identification of tractable biochemical targets for insecticides are discussed. Next, this perspective discusses the movement of insecticide science into the "genomic era" and for comparative purposes, I provide a retrospective analysis of the impact the release of the human genome had to human pharmaceutical development. Based on this analysis and because the fields of insecticide science and human pharmaceuticals mirror each other, researchers in the field of insecticide science would do well to heed the lessons learned by the human pharmaceutical industry and to carefully consider the challenges that arise from genomic approaches for chemical development. Lastly, I pose the question if the field of insecticide science would benefit from adapting an industry-academia model through the generation of industry-sponsored centers of excellence. The goal of this article is not to definitively describe strategies to enhance insecticide development, but rather present different thoughts on agrochemical development that will foster discussions among academic, government, and industry scientists to address current and future problems in the field of insecticide science.

The Challenge of Feeding the World

The aim of the present research is to provide a comprehensive review about the current challenges related to food security and hidden hunger. Issues are presented according to major factors, such as growing population, changing dietary habits, water efficiency, climate change and volatile food prices. These factors were compiled from reports of major international organizations and from relevant scientific articles on the subject. Collecting the results and presenting them in an accessible manner may provide new insight for interested parties. Accessibility of data is extremely important, since food security and its drivers form a closely interconnected but extremely complex network, which requires coordinated problem solving to resolve issues. According to the results, the demand for growing agricultural products has been partly met by increasing cultivated land in recent decades. At the same time, there is serious competition for existing agricultural areas, which further limits the extension of agricultural land in addition to the natural constraints of land availability. Agricultural production needs to expand faster than population growth without further damage to the environment. The driving force behind development is sustainable intensive farming, which means the more effective utilization of agricultural land and water resources. Current global trends in food consumption are unsustainable, analyzed in terms of either public health, environmental impacts or socio-economic costs. The growing population should strive for sustainable food consumption, as social, environmental and health impacts are very important in this respect as well. To this end, the benefits of consuming foods that are less harmful to the environment during production are also to be emphasized in the scope of consumption policy and education related to nutrition as opposed to other food types, the production of which causes a major demand for raw materials.

Dehydrozingerone Inspired Discovery of Potential Broad-Spectrum Fungicidal Agents as Ergosterol Biosynthesis Inhibitors

A series of dehydrozingerone derivatives were synthesized, and their fungicidal activities and action mechanism against Colletotrichum musae were evaluated. The bioassay result showed that most compounds exhibited excellent fungicidal activity in vitro at 50 μg mL^-1. Compounds 13, 16, 18, 19, and 27 exhibited broad-spectrum fungicidal activity; especially, compounds 19 and 27 were found to have more potent fungicidal activity than azoxystrobin. The EC₅₀ values of compounds 19 and 27 against Rhizoctonia solani were 0.943 and 0.161 μg mL^-1 respectively. Moreover, compound 27 exhibited significant in vitro bactericidal activity against Xanthomonas oryzae pv. oryzae, with an EC₅₀ value of 11.386 μg mL^-1, and its curative effect (49.64%) and protection effect (51.74%) on rice bacterial blight disease was equivalent to that of zhongshengmycin (42.90%, 40.80% respectively). Compound 27 could also effectively control gray mold (87.10%, 200 μg mL^-1) and rice sheath blight (100%, 200 μg mL^-1; 82.89%, 100 μg mL^-1) in vivo. Preliminary action mechanism study showed that compound 27 mainly acted on the cell membrane and significantly inhibited ergosterol biosynthesis in Colletotrichum musae.

Synthesis, Biological Evaluation and In Silico Computational Studies of 7-Chloro-4-(1H-1,2,3-triazol-1-yl)quinoline Derivatives: Search for New Controlling Agents against Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae

The insecticidal and antifeedant activities of five 7-chloro-4-(1H-1,2,3-triazol-1-yl)quinoline derivatives were evaluated against the maize armyworm, Spodoptera frugiperda (J.E. Smith). These hybrids were prepared through a copper-catalyzed azide alkyne cycloaddition (CuAAC, known as a click reaction) and displayed larvicidal properties with LD₅₀ values below 3 mg/g insect, and triazolyl-quinoline hybrid 6 showed an LD₅₀ of 0.65 mg/g insect, making it 2-fold less potent than methomyl, which was used as a reference insecticide (LD₅₀ = 0.34 mg/g insect). Compound 4 was the most active antifeedant derivative (CE₅₀ = 162.1 μg/mL) with a good antifeedant index (56-79%) at concentrations of 250-1000 μg/mL. Additionally, triazolyl-quinoline hybrids 4-8 exhibited weak inhibitory activity against commercial acetylcholinesterase from Electrophorus electricus (electric-eel AChE) (IC₅₀ = 27.7 μg/mL) as well as low anti-ChE activity on S. frugiperda larvae homogenate (IC₅₀ = 68.4 μg/mL). Finally, molecular docking simulations suggested that hybrid 7 binds to the catalytic active site (CAS) of this enzyme and around the rim of the enzyme cavity, acting as a mixed (competitive and noncompetitive) inhibitor like methomyl. Triazolyl-quinolines 4-6 and 8 inhibit AChE by binding over the perimeter of the enzyme cavity, functioning as noncompetitive inhibitors. The results described in this work can help to identify lead triazole structures from click chemistry for the development of insecticide and deterrent products against S. frugiperda and related insect pests.

Enzyme and pH dual-responsive avermectin nano-microcapsules for improving its efficacy

The overdosage use of pesticide was harmful to the environment and human health, which was mainly caused by the low utilization rate of the pesticide. However, the pesticide microcapsule with sustained-release and stimulating response properties could effectively solve this problem. Preparation of carboxymethyl cellulose grafting dimethyldiallylammonium chloride (CMC-g-PDMDAAC) through grafting polymerization and trapping as well as encapsulation of avermectin (AVM) via electrostatic interactions resulted in the formation of AVM/CMC-g-PDMDAAC microcapsules. The results showed that the particle size was 200~300 nm. The encapsulation efficiency was as high as 72.06%. Furthermore, the remaining rate of encapsulated AVM increased from 50.0 to 81.60% after UV irradiation for 359 min. The microcapsules exhibited significant enzyme and pH stimuli responsiveness. Finally, CMC-g-PDMDAAC had no significant difference effect on the toxicity of AVM, AVM could be found, and DMDAAC featured a synergistic effect on the toxicological effects of AVM. Graphical abstract.

Discovery of a Novel Series of Tricyclic Oxadiazine 4a-Methyl Esters Based on Indoxacarb as Potential Sodium Channel Blocker/Modulator Insecticides

Indoxacarb, a commercialized oxadiazine insecticide, nearly irreversibly blocks open/inactivated, but not resting sodium channels. The structure-activity relationships showed that the substituents at the position of the chiral atom in the oxadiazine ring are very important to the biological activity of oxadiazine insecticide. Here we synthesized a series of tricyclic oxadiazine 4a-methyl ester derivatives. The chiral atom in the oxadiazine ring has been epimerized and substituted with either pyrethric acid or cinnamic acid derivatives. Benzene ring in the tricyclic moiety was substituted with a chlorine, fluorine, or bromine atom, and nitrogen-linked benzene ring was substituted with a trifluoromethyl or trifluoromethoxy group. Toxicity of these compounds against Spodoptera litura F. was evaluated. Diastereoisomers of most toxic compounds J7 and J9 with pyrethric acid moiety were separated by flash column chromatography. The more polar diastereoisomers, J7-L-Rf and J9-L-Rf, and compounds J24 and J26 with cinnamic acid moiety exhibited highest insecticidal activities. We further used Monte Carlo energy minimizations to dock compound J7 and J24 in the NavMs-based homology model of the open cockroach sodium channel. In the low-energy binding modes, the compound interacted with residues in the inner pore and domain interfaces, which previously were proposed to contribute to receptors of pyrethroids and sodium channel blocker insecticides. Our results define compound J7 and J24 as a potentially useful optimized hit for the development of multiple sites sodium channel blocker or modulator.

Soil mobility of synthetic and virus-based model nanopesticides

Large doses of chemical pesticides are required to achieve effective concentrations in the rhizosphere, which results in the accumulation of harmful residues. Precision farming is needed to improve the efficacy of pesticides, but also to avoid environmental pollution, and slow-release formulations based on nanoparticles offer one solution. Here, we tested the mobility of synthetic and virus-based model nanopesticides by combining soil column experiments with computational modelling. We found that the tobacco mild green mosaic virus and cowpea mosaic virus penetrate soil to a depth of at least 30 cm, and could therefore deliver nematicides to the rhizosphere, whereas the Physalis mosaic virus remains in the first 4 cm of soil and would be more useful for the delivery of herbicides. Our experiments confirm that plant viruses are superior to synthetic mesoporous silica nanoparticles and poly(lactic-co-glycolic acid) for the delivery and controlled release of pesticides, and could be developed as the next generation of pesticide delivery systems.

Sulfone-Based Probes Unraveled Dihydrolipoamide S-Succinyltransferase as an Unprecedented Target in Phytopathogens

Target validation of current drugs remains the major challenge for target-based drug discovery, especially for agrochemical discovery. The bactericide 0 represents a novel lead structure and has shown potent efficacy against those diseases that are extremely difficult to control, such as rice bacterial leaf blight. However, no detailed target analysis of this bactericide has been reported. Here, we developed a panel of 0-derived probes 1-6, in which a conservative modification (alkyne tag) was introduced to keep the antibacterial activity of 0 and provide functionality for target identification via click chemistry. With these cell-permeable probes, we were able to discover dihydrolipoamide S-succinyltransferase (DLST) as an unprecedented target in living cells. The probes showed good preference for DLST, especially probe 1, which demonstrated distinct selectivity and reactivity. Also, we reported 0 as the first covalent DLST inhibitor, which has been used to confirm the involvement of DLST in the regulation of energy production.

Modeling of the Binding of Octopamine and Dopamine in Insect Monoamine Transporters Reveals Structural and Electrostatic Differences

Octopamine, a trace amine in mammals, is a major neurotransmitter linked to important biological processes in insects. Interestingly, one of the molecular entities responsible for octopamine availability, the octopamine transporter (OAT), has not been identified in certain insect species. For instance, no OAT has been reported in the fly Drosophila melanogaster (Dm), and the molecule involved in octopamine reuptake in Drosophila is not known. Here, we used molecular modeling methodologies to obtain three-dimensional insights for the dopamine transporter (DAT) and OAT in a common agricultural pest insect, Trichoplusia ni (Tni). Our results show several similarities but also significant differences in the general structures of the proteins of Dm and Tni. One important difference is observed in the ligand binding cavity, where a negatively charged amino acid present in both dopamine transporters is replaced by a polar neutral residue in the Trichoplusia OAT. This modification could influence both the binding mode and the driving force involved in the transport mechanism of these amines into neurons of these species. We also obtained data that support the idea that octopamine could bind and possibly be transported by DmDAT. The structural characterization of macromolecules from different insect species is fundamental in the agricultural field to gain insights into the design of new compounds for controlling pests.

Chemical Modulation of Alternative Splicing for Molecular-Target Identification by Potential Genetic Control in Agrochemical Research

Alternative splicing (AS), the process of removing introns from pre-mRNA and the rearrangement of exons to produce several types of mature transcripts, is a remarkable step preceding protein synthesis. In particular, it has now been conclusively shown that up to ∼95% of genes are alternatively spliced to generate a complex and diverse proteome in eukaryotic organisms. Consequently, AS is one of the determinants of the functional repertoire of cells. Many studies have revealed that AS in plants can be regulated by cell type, developmental stage, environmental stress, and the circadian clock. Moreover, increasing amounts of evidence reveal that chemical compounds can affect various steps during splicing to induce major effects on plant physiology. Hence, the chemical modulation of AS can serve as a good strategy for molecular-target identification in attempts to potentially control plant genetics. However, the kind of mechanisms involved in the chemical modulation of AS that can be used in agrochemical research remain largely unknown. This review introduces recent studies describing the specific roles AS plays in plant adaptation to environmental stressors and in the regulation of development. We also discuss recent advances in small molecules that induce alterations of AS and the possibility of using this strategy in agrochemical-target identification, giving a new direction for potential genetic control in agrochemical research.

Local applications but global implications: Can pesticides drive microorganisms to develop antimicrobial resistance?

Pesticides are an important agricultural input, and the introduction of new active ingredients with increased efficiencies drives their higher production and consumption worldwide. Inappropriate application and storage of these chemicals often contaminate plant tissues, air, water, or soil environments. The presence of pesticides can lead to developing tolerance, resistance or persistence and even the capabilities to degrade them by the microbiomes of theses environments. The pesticide-degrading microorganisms gain and employ several mechanisms for attraction (chemotaxis), membrane transport systems, efflux pumps, enzymes and genetical make-up with plasmid and chromosome encoded catabolic genes for degradation. Even the evolution and the mechanisms of inheritance for pesticide-degradation as a functional trait in several microorganisms are beginning to be understood. Because of the commonalities in the microbial responses of sensing and uptake, and adaptation due to the selection pressures of pesticides and antimicrobial substances including antibiotics, the pesticide-degraders have higher chances of possessing antimicrobial resistance as a surplus functional trait. This review critically examines the probabilities of pesticide contamination of soil and foliage, the knowledge gaps in the regulation and storage of pesticide chemicals, and the human implications of pesticide-degrading microorganisms with antimicrobial resistance in the global strategy of 'One Health'.

FungiPAD: A Free Web Tool for Compound Property Evaluation and Fungicide-Likeness Analysis

The increasing prevalence of fungal diseases, continual development of resistance, and stringent environmental regulations have revealed an urgent need to develop more selective, safer, resistance-breaking, and cost-effective fungicides. However, most new fungicidal lead compounds fail in their late stages of development as a result of poor solubility or permeability, meaning that they have suboptimal physicochemical properties. Hence, the exploration of advanced technologies for compound "fungicide-likeness" assessment might overcome these obstacles and bring more chemical entities to market. FungiPAD ( http://chemyang.ccnu.edu.cn/ccb/database/FungiPAD/ ) is a free platform employed to predict physicochemical properties, bioavailability, and fungicide-likeness swiftly and powerfully using comprehensive approaches, such as physicochemical radars and qualitative and quantitative analyses. This platform contains data for over 16 000 physicochemical descriptors and the results of 2200 qualitative and 1100 quantitative analyses of marketed fungicides and provides comprehensive fungicide-likeness analysis for different compounds. The user-friendly interface facilitates interpretation and manipulation by non-computational scientists in support of fungicide discovery.

Nano-based smart pesticide formulations: Emerging opportunities for agriculture

The incorporation of nanotechnology as a means for nanopesticides is in the early stage of development. The main idea behind this incorporation is to lower the indiscriminate use of conventional pesticides to be in line with safe environmental applications. Nanoencapsulated pesticides can provide controlled release kinetics, while efficiently enhancing permeability, stability, and solubility. Nanoencapsulation can enhance the pest-control efficiency over extended durations by preventing the premature degradation of active ingredients (AIs) under harsh environmental conditions. This review is thus organized to critically assess the significant role of nanotechnology for encapsulation of AIs for pesticides. The smart delivery of pesticides is essential to reduce the dosage of AIs with enhanced efficacy and to overcome pesticide loss (e.g., due to leaching and evaporation). The future trends of pesticide nanoformulations including nanomaterials as AIs and nanoemulsions of biopesticides are also explored. This review should thus offer a valuable guide for establishing regulatory frameworks related to field applications of these nano-based pesticides in the near future.