Targeted and non-targeted analysis for the investigation of pesticides influence on wheat cultivated under field conditions

Study of pesticide transformation processes in different wheat varieties and their effects on plant metabolism

BACKGROUND

This study aims to obtain systematic understanding of the way by which pesticides are metabolized in plants and the influence of this process on plants' metabolism as this process has a key impact on plant-based food safety and quality. The research was conducted under field conditions, which enabled to capture metabolic processes taking place in plants grown under multihectare cultivation conditions.

RESULTS

Research was conducted on three wheat varieties cultivated under field conditions and treated by commercially available preparations (fungicides, herbicides, insecticides, and growth regulator). Plant tissues with distinctions in roots, green parts, and ears were collected periodically during spring-summer vegetation period, harvested grains were also investigated. Sample extracts were examined by chromatographic techniques coupled with tandem mass spectrometry for: dissipation kinetics study, identification of pesticide metabolites, and fingerprint-based assessment of metabolic changes.

CONCLUSION

Tissue type and wheat varieties influenced pesticide dissipation kinetics and resulting metabolites. Metabolic changes of plants were influenced by type of applied pesticide and its concentration in plants tissues. Despite differences in plant metabolic response to pesticide stress during cultivation, grain metabolomes of all investigated wheat varieties were statistically similar. 4-[cyclopropyl(hydroxy)methylidene]-3,5-dioxocyclo-hexanecarboxylic acid and trans-chrysantemic acid - metabolites of crop-applied trinexapac-ethyl and lambda-cyhalothrin, respectively, were identified in cereal grains. These compounds were not considered to be present in cereal grains up to now. The research was conducted under field conditions, enabling the measurement of metabolic processes taking place in plants grown under large-scale management conditions. © 2024 Society of Chemical Industry.

Evaluation of the Morphological, Physiological and Biochemical Effects Induced by Coragen 20 SC in Some Non-Target Species

Coragen 20 SC is an insecticide based on chlorantraniliprole that is applied on many crops. Considered an effective product with an incremental cost-benefit ratio, it has been widely used globally. Residual pesticides affect non-target organisms, so it is necessary to explore the possible effects induced by these xenobiotics on different species. This work aimed to assess some morphological, physiological and biochemical effects induced by Coragen 20 SC on two non-target species: Perca fluviatilis (Linné, 1758) and Triticum aestivum L. The concentrations used were the same for all tested species (0.0125, 0.025 and 0.05 mL L^-1), and the experiments were of the acute, subchronic and chronic type. The toxicological effects of Coragen 20 SC on perch recorded behavioral changes, a decrease in respiratory rate and oxygen consumption, an increase in blood glucose levels and a decrease in the number of erythrocytes and leukocytes. The results obtained from the evaluation of Coragen 20 SC toxicity using the Triticum test indicate a weak to moderate phytotoxicity for the considered parameters at the applied doses. Only the assimilatory pigments were significantly modified at the concentration of 0.025 mL L^-1 for the growth of the axial organs and the wet and dry weight, with the changes obtained not being statistically significant.

The metabolic processes of selected pesticides and their influence on plant metabolism. A case study of two field-cultivated wheat varieties

Pesticides that are absorbed by plants undergo biotransformation and might affect plant metabolic processes. The metabolisms of two cultivated wheat varieties, Fidelius and Tobak, treated with commercially available fungicides (fluodioxonil, fluxapyroxad, and triticonazole) and herbicides (diflufenican, florasulam, and penoxsulam) were studied under field conditions. The results provide novel insights regarding the effects of these pesticides on plant metabolic processes. Plants (roots and shoots) were sampled six times during the six-week experiment. Pesticides and pesticide metabolites were identified using GC-MS/MS, LC-MS/MS, and LC-HRMS, while root and shoot metabolic fingerprints were determined using non-targeted analysis. Fungicide dissipation kinetics were analyzed according to the quadratic mechanism (R²: 0.8522-0.9164) for Fidelius roots, and zero-order for Tobak roots (R²: 0.8455-0.9194); shoot dissipation kinetics were analyzed according to first-order (R²: 0.9593-0.9807) and quadratic (R²: 0.8415-0.9487) mechanisms for Fidelius and Tobak, respectively. The fungicide degradation kinetics were different compared to reported literature values, most likely due to differences in pesticide application methods. The following metabolites were respectively identified in shoot extracts of both wheat varieties for fluxapyroxad, triticonazole, and penoxsulam: 3-(difluoromethyl)-N-(3',4',5'-trifluorobiphenyl-2-yl)-1H pyrazole-4-carboxamide, 2-chloro-5-{(E)-[2-hydroxy-3,3-dimethyl-2-(1H-1,2,4-triazol-1-ylmethyl)-cyclopentylidene]-methyl}phenol, and N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-2,4-dihydroxy-6 (trifluoromethyl)benzene sulfonamide. Metabolite dissipation kinetics varied depending on the wheat variety. These compounds were more persistent than parent compounds. Despite having the same cultivation conditions, the two wheat varieties varied in their metabolic fingerprints. The study revealed that pesticide metabolism has a greater dependence on plant variety and method of administration compared to the physicochemical properties of the active substance. This highlights the necessity of conducting research on pesticide metabolism under field conditions.

Demonstrating the Use of Non-targeted Analysis for Identification of Unknown Chemicals in Rapid Response Scenarios

Several thousand intentional and unintentional chemical releases occur annually in the U.S., with the contents of almost 30% being of unknown composition. When targeted methods are unable to identify the chemicals present, alternative approaches, including non-targeted analysis (NTA) methods, can be used to identify unknown analytes. With new and efficient data processing workflows, it is becoming possible to achieve confident chemical identifications via NTA in a timescale useful for rapid response (typically 24-72 h after sample receipt). To demonstrate the potential usefulness of NTA in rapid response situations, we have designed three mock scenarios that mimic real-world events, including a chemical warfare agent attack, the contamination of a home with illicit drugs, and an accidental industrial spill. Using a novel, focused NTA method that utilizes both existing and new data processing/analysis methods, we have identified the most important chemicals of interest in each of these designed mock scenarios in a rapid manner, correctly assigning structures to more than half of the 17 total features investigated. We have also identified four metrics (speed, confidence, hazard information, and transferability) that successful rapid response analytical methods should address and have discussed our performance for each metric. The results reveal the usefulness of NTA in rapid response scenarios, especially when unknown stressors need timely and confident identification.