Mechanisms of adsorption and functionalization of biochar for pesticides: A review.

Agricultural production relies heavily on pesticides. However, factors like inefficient application, pesticide resistance, and environmental conditions reduce their effective utilization in agriculture. Subsequently, pesticides transfer into the soil, adversely affecting its physicochemical properties, microbial populations, and enzyme activities. Different pesticides interacting can lead to combined toxicity, posing risks to non-target organisms, biodiversity, and organism-environment interactions. Pesticide exposure may cause both acute and chronic effects on human health. Biochar, with its high specific surface area and porosity, offers numerous adsorption sites. Its stability, eco-friendliness, and superior adsorption capabilities render it an excellent choice. As a versatile material, biochar finds use in agriculture, environmental management, industry, energy, and medicine. Added to soil, biochar helps absorb or degrade pesticides in contaminated areas, enhancing soil microbial activity. Current research primarily focuses on biochar produced via direct pyrolysis for pesticide adsorption. Studies on functionalized biochar for this purpose are relatively scarce. This review examines biochar's pesticide absorption properties, its characteristics, formation mechanisms, environmental impact, and delves into adsorption mechanisms, functionalization methods, and their prospects and limitations.

Effects of wheat varieties, fungicides and application time on Fusarium head blight and deoxynivalenol contamination control in wheat.

BACKGROUND: Yield loss and toxin contamination caused by wheat Fusarium head blight (FHB) have always been a worldwide concern. Cultivating disease-resistant varieties and fungicide application are effective measures to control FHB. The comprehensive control technology system for FHB and toxin contamination of wheat in Anhui Province needs further improvement. This study compared the control efficacy of different wheat varieties, fungicides and application times on wheat FHB and deoxynivalenol (DON) contamination, and the dynamic change of DON accumulation after application. RESULTS: Among the 93 main wheat varieties in Anhui Province, the disease-resistant and low-toxic wheat variety "Ningmai 26" was more suitable for planting in the central part of Anhui Province. At the same time, "Yangmai 22" was used for subsequent experiments. The field efficacy trials of different fungicides showed that 30% prothioconazole oil dispersion (OD) had the highest control efficacy on FHB and DON contamination, reaching 94.33 and 77.49%, respectively. The study on the optimum application time of prothioconazole showed that the 0-20% flowering stage was the key point of DON control. The survey of the dynamic changes of DON accumulation showed that prothioconazole could significantly reduce the level of DON accumulation while inhibiting the accumulation rate of DON. At the same time, the control fungicide carbendazim increased the level of DON contamination. CONCLUSION: This study will provide excellent germplasm resources for cultivating disease-resistant and low-toxic wheat varieties, and provide a theoretical reference for establishing a collaborative prevention and control system of disease control and toxin reduction. © 2023 Society of Chemical Industry.

Degradation, adsorption, and bioaccumulation of novel triketone HPPD herbicide tembotrione.

Tembotrione is a new triketone HPPD herbicide widely used in Europe, USA, and other areas. However, tembotrione is moderately to highly toxic to algae and daphnia in aquatic ecosystems. In this study, hydrolysis, photolysis, soil degradation, soil adsorption, and bioaccumulation of tembotrione were systematically studied. Hydrolysis experiment revealed that tembotrione was stable in acidic, neutral, and alkaline conditions with half-lives of 231-289 days. The photolysis half-lives of tembotrione were 112-158 days and 76-107 days in pH 4, 7, 9 buffer solutions and on three soils surface, respectively, which demonstrated that tembotrione could be persisted in soil and water. Meanwhile, tembotrione Kfoc was 128-196 mL/g, indicating that tembotrione was not easily adsorbed to soil, and the adsorption capacity increased with the decrease in pH. The half-lives of tembotrione in the test soil were 32-48 days, and high organic matter soil is conducive to microbial activity and accelerates the degradation of tembotrione. Moreover, bioaccumulation experiment demonstrated that tembotrione with a BCF of 0.664 to 0.724 had a low risk of exposure to zebrafish. This study is very helpful for the evaluation environmental risk and safe use of tembotrione.

A Specific High Toxicity of Xinjunan (Dioctyldiethylenetriamine) to Xanthomonas by Affecting the Iron Metabolism.

Xanthomonas spp. encompass a wide range of phytopathogens that brings great economic losses to various crops. Rational use of pesticides is one of the effective means to control the diseases. Xinjunan (Dioctyldiethylenetriamine) is structurally unrelated to traditional bactericides, and is used to control fungal, bacterial, and viral diseases with their unknown mode of actions. Here, we found that Xinjunan had a specific high toxicity toward Xanthomonas spp., especially to the Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial leaf blight. Transmission electron microscope (TEM) confirmed its bactericidal effect by morphological changes, including cytoplasmic vacuolation and cell wall degradation. DNA synthesis was significantly inhibited, and the inhibitory effect enhanced with the increase of the chemical concentration. However, the synthesis of protein and EPS was not affected. RNA-seq revealed differentially expressed genes (DEGs) particularly enriched in iron uptake, which was subsequently confirmed by siderophore detection, intracellular Fe content and iron-uptake related genes transcriptional level. The laser confocal scanning microscopy and growth curve monitoring of the cell viability in response to different Fe condition proved that the Xinjunan activity relied on the addition of iron. Taken together, we speculated that Xinjunan exerted bactericidal effect by affecting cellular iron metabolism as a novel mode of action. IMPORTANCE Sustainable chemical control for rice bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae need to be developed due to limited bactericides with high efficiency, low cost, and low toxicity in China. This present study verified a broad-spectrum fungicide named Xinjunan possessing a specific high toxicity to Xanthomonas pathogens, which were further confirmed by affecting the cellular iron metabolism of Xoo as a novel mode of action. These findings will contribute to the application of the compound in the field control of Xanthomonas spp.-caused diseases, and be directive for future development of novel specific drugs for the control of severe bacterial diseases based on this novel mode of action.

Stereoselective bioactivity, toxicity and degradation of novel fungicide sedaxane with four enantiomers under rice-wheat rotation mode.

Sedaxane was a novel chiral fungicide that contains four enantiomers. Unfortunately, the stereoselective bioactivity, toxicity and degradation of sedaxane have not been clarified. In this study, we identified the absolute configuration of the four sedaxane enantiomers at first time. The stereoselective bioactivity toward three wheat and rice pathogens, stereoselective acute toxicity to aquatic organisms (Selenastrum capricornutum and Daphnia magna), and stereoselective degradation of sedaxane were studied. The 1 S,2S-(+)-sedaxane possessed 5.4-7.3 times greater bioactivity than 1 R,2R-(-)-sedaxane to Rhizoctonia solani and Rhizoctonia cerealis. Contrarily, the 1 R,2S-(+)-sedaxane had 4.2 times greater activity than 1 S,2S-(+)-sedaxane against Fusarium graminearum. The 1 R,2R-(-)-sedaxane had 2.8 times greater toxicity than 1 S,2S-(+)-sedaxane to S. capricornutum. The chiral determination method used ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The recovery of sedaxane stereoisomers ranged from 83.1 % to 98.2 %, with RSDs (Relative standard deviations) of 1.2 %- 8.4 %. The trans-sedaxane existed stereoselective degradation phenomenon in the rice-wheat rotation mode, and 1 S,2S-(+)-sedaxane was preferentially degraded. Our results would provide scientific importance and practical guidance to the safety evaluation of chiral pesticides.

Systemic assessment of the chiral insecticide pyriproxyfen in a citrus nectar source system: Stereoselective degradation, biological effect and exposure risk.

BACKGROUND: Balancing the safety and efficiency of chiral pesticides can help protect pollinators. We evaluated the stereoselective behavior, bioactivity, toxicity and exposure risk of the chiral insecticide pyriproxyfen in a citrus nectar system. RESULTS: Density functional theory (DFT) and ultra-performance liquid chromatography tandem mass spectroscopy (UPLC-MS/MS) were applied for absolute configuration appraisal and chiral analysis validation, respectively. The recoveries ranged from 72.3% to 100.5% with an relative standard deviation (RSD) ranging from 1.2% to 9.7%. In a field trial, we determined insecticide half-lives in citrus leaves and flowers, which were 7.0 and 8.6 days for R-(+)-pyriproxyfen, and 11.7 and 14.7 days for S-(-)-pyriproxyfen, respectively. We found that the bioactivity of R-(+)-pyriproxyfen was 3.39 and 2.37 times higher than S-(-)-pyriproxyfen against Unaspis yanonensis and Diaphorina citri nymphs, respectively. S-(-)-pyriproxyfen had 3.8 times higher acute toxicity than R-(+)-pyriproxyfen on Apis mellifera L., and its exposure risk was moderate based on the hazard quotient. CONCLUSION: The phenomenon of stereoselective degradation and biological effect demonstrated that the high-risk stereoisomer of S-(-)-pyriproxyfen degraded more slowly than R-(+)-pyriproxyfen, but R-(+)-pyriproxyfen with better efficiency for target. Therefore, an increased duration of R-(+)-pyriproxyfen activity on citrus was beneficial for efficacy. Our results could guide the scientific application and evaluation of chiral pesticides on nectar plants. © 2022 Society of Chemical Industry.

A Defect in the Twin-Arginine Translocation Pathway Decreases the Tolerance of Xanthomonas campestris pv. campestris to Phenazines.

Phenazine-1-carboxylic acid (PCA), a member of phenazines secreted by microorganisms, inhibits the growth of many bacteria and fungi. Xanthomonas campestris pv. campestris is the causal agent of black rot, the most important disease of cruciferous crops worldwide, and is more tolerant to PCA than other Xanthomonas species. Previous studies reported that reactive oxygen species (ROS) scavenging ability is involved in regulating the PCA tolerance of Xanthomonas species. Additionally, the cytochrome c maturation (CCM) system has been found to play a more important role in tolerance to phenazines than the ROS scavenging system. In this study, a highly PCA-sensitive insertion mutant of X. campestris pv. campestris, X-5, was identified and studied. The insertion site of X-5 was found to be in tatB gene (XC_4183), which encodes a subunit of the twin-arginine translocation (TAT) complex. Disruption of the three genes of TAT pathway resulted in decreased biological fitness and reduced tolerance to phenazines in comparison with the wild-type strain 8004. These results imply that the tolerance mechanism of the TAT pathway to phenazines is related to the CCM system, but not due to the ROS scavenging system. Furthermore, respiration-related characteristic tests and peptide analysis suggested that disruption of the TAT complex causes a defect in the cytochrome bc1 complex, which may be involved in the tolerance to phenazines. In summary, this study sheds new light on the critical role of the TAT pathway in influencing the fitness and phenazines tolerance of Xanthomonas species.

Rapid Detection of Alternaria Species Involved in Pear Black Spot Using Loop-Mediated Isothermal Amplification.

Alternaria species are the most important fungal pathogens that attack various crops as well as fruit trees such as pear and cause black spot disease. Here, a loop-mediated isothermal amplification (LAMP) assay is developed for the detection of Alternaria species. A. alternata cytochrome b (cyt-b) gene was used to design two pairs of primers and amplified a 229-bp segment of Aacyt-b gene. The results showed that LAMP assay is faster and simpler than polymerase chain reaction (PCR). LAMP assay is highly sensitive method for the detection of about 1 pg of genomic DNA of A. alternata by using optimized concentration of MgCl2 (4 mM) in final LAMP reaction. In contrast, the limit of detection was 1 ng of target DNA via conventional PCR. Among the genomic DNA of 46 fungal species, only the tubes containing DNA of Alternaria spp. except A. porri, A. solani, and A. infectoria changed color from orange to yellowish green with SYBR Green I including the main pathogens of pear black spot. The yellowish green color was indicative of DNA amplification. Moreover, LAMP assay was used for testing infected tissues among 22 healthy and diseased pear tissues; the orange color changed to yellowish green for infected tissues only. Altogether, we conclude that cyt-b gene can be used for the detection of Alternaria spp. via LAMP assay, which is involved in pear black spot disease.

Determination of phenamacril residues in flour and rice based on Z-Sep+ using ultra-high-performance liquid chromatography-tandem mass spectrometry.

Phenamacril is a new broad-spectrum fungicide that is commonly used for the control of fungal diseases in wheat and rice. In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry was used to establish a method for analyzing the residual phenamacril in flour and rice based on the improved QuEChERS (quick, easy, cheap, effective, rugged and safe) method using Z-Sep+ as the adsorbent in the pre-treatment process. The average recovery of phenamacril in flour and rice was 82.2-96.0%, the relative standard deviation was 2.1-5.6% and the limit of quantification was 0.5 µg/kg. The accuracy and sensitivity of this method meet the requirements for residue analysis. The method was applied to commercially available flour and rice samples, and the detected concentrations of phenamacril were 0.005-0.033 mg/kg. This method provides technical support for the safety evaluation of phenamacril.

Dissipation of Prothioconazole and Its Metabolite Prothioconazole-Desthio in Rice Fields and Risk Assessment of Its Dietary Intake.

Rice is an important food crop, with a long history of cultivation in China, and is one of the important staple foods for Chinese today. However, the occurrence of rice diseases has had a substantial impact on its yield. At present, chemical control is the main means of prevention and control of rice diseases. As a high-efficacy and broad-spectrum fungicide, prothioconazole shows an ideal effect on the prevention and control of common rice diseases, but the residuals that remain after its use may have an impact on human health. In this paper, ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to develop a residue analysis method and explore the dissipation of prothioconazole and its metabolite prothioconazole-desthio in rice grain, rice husk, and rice plants, and the risks of chronic and acute dietary intake of prothioconazole in different Chinese populations were evaluated. The results showed that at a concentration range of 0.005-5.0 µg/mL, prothioconazole and its metabolites showed good linear correlations, and the correlation coefficients were all above 0.9992. The average recoveries of prothioconazole in three matrixes ranged from 80.0% to 99.7%, the RSD was between 1.54% and 11.0%, and the limit of quantitation was less than 0.01 µg/g. The sensitivity, accuracy, and precision of the established method all met the measurement requirements. The dissipation experimental results showed that the parent compound prothioconazole was rapidly metabolized to prothioconazole-desthio in the rice field environment, and the dissipation half-life in rice plants after application was 2.5-10.1 d. According to the results of dietary risk assessment, under the standardized residue test conditions, the residual level of rice at the sampling interval of 7 days was within the acceptable range for the chronic and acute dietary risks of different populations in China. Our research is important for directing the scientific application of pesticides in China.

Mannan oligosaccharides trigger multiple defence responses in rice and tobacco as a novel danger-associated molecular pattern.

Oligosaccharide, a typical danger-associated molecular pattern (DAMP), has been studied and applied as plant defence elicitor for several years. Here, we report a novel oligosaccharide, mannan oligosaccharide (MOS) with a degree of polymerization of 2-6, which was hydrolysed from locust bean gum by a newly reported enzyme, BpMan5. The MOS treatment can significantly enhance the generation of signalling molecules such as intracellular Ca2+ and reactive oxygen species. Subsequent defence events like stomata closure and cell death were also caused by MOS, eventually leading to the prevention of pathogen invasion or expansion. Transcriptional expression assay indicated that MOS activated mitogen-activated protein kinase cascades in tobacco and rice via different cascading pathways. The expression levels of the defence-related genes PR-1a and LOX were both up-regulated after MOS treatment, suggesting that MOS may simultaneously activate salicylic acid and jasmonic acid-dependent signalling pathways. Furthermore, liquid chromatography-mass spectrometry analysis showed that MOS led to the accumulation of four phytoalexins (momilactone A, phytocassane A, phytocassane D, and phytocassane E) in rice seedling leaves within 12-24 h. Finally, MOS conferred resistance in rice and tobacco against Xanthomonas oryzae and Phytophthora nicotianae, respectively. Taken together, our results indicated that MOS, a novel DAMP, could trigger multiple defence responses to prime plant resistance and has a great potential as plant defence elicitor for the management of plant disease.

Determination of the Residue Behavior and Risk Assessment of Chlorfluazuron in Chinese Cabbage, Kale, Lettuce and Cauliflower by UPLC-MS/MS.

Chlorfluazuron is used as a highly effective insect growth regulator to control a variety of crop pests. However, residues of this pesticide have been shown to be harmful to human health. To evaluate the residual dissipation pattern and risk for dietary intake of chlorfluazuron in various vegetables, a solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry method was established to analyze chlorfluazuron residues in Chinese cabbage, Chinese kale, Chinese lettuce, and cauliflower. The sample was extracted with acetonitrile and purified using an SPE amino column. The average recovery of the target sample in the analyzed four vegetables was between 75.0% and 104.1%, and the relative standard deviation was between 2.5% and 9.6%. The precision and accuracy of the analysis met the requirements of residue analysis standards. Dissipation kinetic testing of chlorfluazuron in different vegetables showed a half-life of 2.4-12.6 days, with a rapid dissipation rate. The estimated daily intake of the chlorfluazuron was 0.753-1.661 µg/(kg bw·d), and the risk quotient was 0.15-0.35. It showed that chlorfluazuron had a low risk of chronic dietary intake from vegetables in different populations in China. The results of this study has described the degradation rate of chlorfluazuron in four vegetables, evaluated the risk of dietary exposure to Chinese residents. Therefore, it provides supporting data and empirical basis for guiding the reasonable use of chlorfluazuron in vegetable production and in evaluating its dietary intake risk in vegetables.

Dissipation Dynamics and Dietary Risk Assessment of Kresoxim-Methyl Residue in Rice.

Kresoxim-methyl is a high-efficiency and broad-spectrum fungicide used for the control of rice fungal diseases; however, its residues after application potentially threaten human health. Investigations on the dissipation of kresoxim-methyl residue in rice field systems and dietary risk assessment of kresoxim-methyl in humans are limited. The present study employed the QuEChERS-GC-MS/MS method for residue analysis of kresoxim-methyl in rice plants, brown rice, and rice husks. The samples were extracted with acetonitrile and purified by PSA, C18 column, and GCB. The average recovery of the spiked target compounds in the three matrices was between 80.5% and 99.3%, and the RSD was between 2.1% and 7.1%. The accuracy and precision of the method is in accordance with the requirements of residue analysis methods. Dissipation dynamic testing of kresoxim-methyl in rice plants indicated a half-life within the range of 1.8⁻6.0 days, and a rapid dissipation rate was detected. Dietary intake risk assessment showed that the national estimated daily intake (NEDI) of kresoxim-methyl in various Chinese subpopulations was 0.022⁻0.054 µg/(kg bw·days), and the risk quotient (RQ) was 0.0000055⁻0.00014%. These findings indicate that the risk for chronic dietary intake of kresoxim-methyl in brown rice is relatively low. The present study provides information and theoretical basis for guiding the scientific use of kresoxim-methyl in rice fields and evaluating its dietary risk in brown rice.

Enantioselective effects of the chiral fungicide tetraconazole in wheat: Fungicidal activity and degradation behavior.

Tetraconazole, a chiral triazole fungicide, is widely used for the prevention of plant disease in wheat fields. However, the chirality of pesticides like tetraconazole can cause diverse biological responses. Therefore, it is important that research is conducted to investigate the enantioselective effects of chiral enantiomers in this regard. The absolute configurations of two tetraconazole enantiomers were initially confirmed by ECD (Electrostatic circular dichroism). The bioassay test showed that the fungicidal activity of (R)-(+)-tetraconazole against two pathogens (R. cerealis and F. graminearum) was approximately 1.49-1.98 times greater than that for (S)-(-)- tetraconazole. Following recovery experiments, a modified QuEchERS (Quick, easy, cheap, effective, rugged, safe) method was established using UPLC-MS/MS (ultra-performance liquid chromatography tandem mass spectrometry). The mean recoveries from plant and soil sample ranged from 78.9% to 100.5% with intraday relative standard (RSDr) values of 0.8%-6.9% and interday relative standard (RSDR) values of 3.0%-5.2% respectively. The stereoselective degradation of tetraconazole in wheat meant that (S)-(-)-tetraconazole was more rapidly degraded than (R)-(+)-tetraconazole. Conversely, (R)-(+)-tetraconazole was preferentially degraded in wheat soil. These results will provide us with a greater understanding when assessing future environmental risk assessments and strategies that invoke pesticide reduction.

Stereoselective analysis of the chiral fungicide penflufen in wheat plants, spinach, and Chinese cabbage.

Penflufen is a highly efficient, broad-spectrum succinate dehydrogenase inhibitor. Owing to the increasing pesticide resistance in recent years, the use of a new fungicide, penflufen, has become increasingly widespread. However, residues that remain in the environment after the use of penflufen have an impact on human health. It is worth noting that penflufen is a chiral pesticide. The differences of residue behaviors between two enantiomers in living organisms need to be systematically studied. In this paper, reversed-phase liquid chromatography-mass spectrometry (LC-MS) was used to separate the enantiomers of penflufen, and the absolute configuration of the enantiomer was analyzed. The LC-MS/MS methods for the analysis of penflufen enantiomers on wheat plants, spinach, and Chinese cabbage were established. The results of the recovery experiments showed that the average recovery of the two enantiomers was 78.5-99.8% and RSD was 0.4-7.3%, suggesting that the accuracy and precision of the method meet the requirements of pesticide residue analysis. The results of stereoselective degradation of penflufen in the three matrices showed that there was little difference in the degradation of the two enantiomers in wheat and cabbage, while R-(+)-penflufen was degraded preferentially in spinach. This study provides data supporting the scientific use and safety evaluation of penflufen.

Enantioselective Acute Toxicity and Bioactivity of Carfentrazone-ethyl enantiomers.

The stereoselective herbicidal bioactivity and toxicity toward aquatic organisms of carfentrazone-ethyl enantiomers were investigated. The results showed that there was significant enantioselective acute toxicity toward Selenastrum bibraianum. In addition, S-(-)-carfentrazone-ethyl was 4.8 times more potent than R-(+)-isomer. However, a slight enantioselectivity was observed for Daphnia magna and Danio rerio. The stereoselective herbicidal bioactivity of carfentrazone-ethyl enantiomers was observed by assessing maize root-length inhibition. The results clarified that S-(-)-carfentrazone-ethyl (EC50 1.94 mg/L) > Rac-carfentrazone-ethyl (EC50 2.18 mg/L) > R-(+)-carfentrazone-ethyl (EC50 3.96 mg/L). The herbicidal bioactivity of S-(-)-carfentrazone-ethyl was 2 times higher more than R-(+)-isomer. The mechanism of enantioselective bioactivity was illustrated using molecular simulation software. The GlideScore energies of S-(-)-carfentrazone-ethyl and R-(+)-carfentrazone-ethyl were - 6.15 kcal/mol and - 5.59 kcal/mol, indicating that the S-form has a greater affinity to the active site of protoporphyrinogen oxidase, which is consistent with the results of the bioactive assay. This study can rise the significance of risk assessments for carfentrazone-ethyl herbicide.

Rapid Detection of Ustilaginoidea virens from Rice using Loop-Mediated Isothermal Amplification Assay.

Ustilaginoidea virens is an important fungus that causes rice false smut disease. This disease significantly reduces both grain yield and quality. Various methods have been developed for the detection of U. virens but most of these methods need sophisticated equipment such as a thermal cycler. Here, we present a loop-mediated isothermal amplification (LAMP) assay for the specific detection of U. virens. This assay used a specific region of the UvG-ß1 gene (212-bp region) to design six LAMP primers. The LAMP assay was optimized by the combination of rapidity, simplicity, and high sensitivity for the detection of about 1 pg of target genomic DNA in the reaction whereas, with polymerase chain reaction (PCR), there was no amplification of DNA with concentrations less than 1 ng. Among the genomic DNA of 22 fungus species and two strains of U. virens, only the tube containing the DNA of U. virens changed to yellowish green with SYBR Green I. The color change was indicative of DNA amplification. No DNA was amplified from either the other 22 fungus species or the negative control. Moreover, 20 spikelets and 22 rice seed samples were used for the detection of rice false smut via LAMP. The results were comparable with conventional PCR. We conclude that gene UvG-ß1 coupled with LAMP assay, can be used for the detection and identification of U. virens gene via LAMP.

Simultaneous determination of enantiomers of carfentrazone-ethyl and its metabolite in eight matrices using high-performance liquid chromatography with tandem mass spectrometry.

A reversed-phase simultaneous determination method for the enantiomers of carfentrazone-ethyl and its metabolite carfentrazone in agricultural and environmental samples was established using high-performance liquid chromatography-tandem mass spectrometry. A complete enantioseparation of carfentrazone-ethyl and its chiral metabolite carfentrazone enantiomers was obtained using a chiral column. The absolute configuration and specific optical rotation of carfentrazone-ethyl and carfentrazone enantiomers were first confirmed as peaks 1, 2, 3, and 4: S-(+)-carfentrazone, R-(-)-carfentrazone, S-(-)-carfentrazone-ethyl, and R-(+)-carfentrazone-ethyl, respectively. The specificity, matrix effect, linearity, precision, accuracy, and stability were surveyed to evaluate the feasibility of the method. The mean recovery was in the range of 77.5-102.8% with relative standard deviations of 0.4-9.8% for the samples. The limits of detection of the enantiomers were evaluated as 0.7 to 6.0 µg/kg, and the limits of quantification were 2.5 to 20 µg/kg. The stereoselective degradation of carfentrazone-ethyl and carfentrazone in rice plant was investigated, and there was no clear enantioselectivity for carfentrazone-ethyl. As for carfentrazone, the enantiomer fractions value reached 0.85 at 7 days after spraying. The developed method was simple and reliable enough for the corresponding risk assessment of carfentrazone-ethyl and its metabolite enantiomers in crop plants, cereal grains, and soil samples.

Stereoselective degradation behaviour of carfentrazone-ethyl and its metabolite carfentrazone in soils.

The stereoselective environmental behaviour of carfentrazone-ethyl and its metabolite carfentrazone enantiomer in three types of soil were studied under aerobic conditions. Under aerobic conditions, significant stereoselective difference in the degradation behaviour of carfentrazone-ethyl and its metabolite carfentrazone enantiomer was observed in Jiangxi red soil, Jilin black soil and Anhui paddy soil. The EF values of the carfentrazone-ethyl enantiomers in Anhui paddy soil, Jilin black soil, and Jiangxi red soil were 0.67, 0.65 and 0.57, respectively. The EF values of the carfentrazone enantiomer in the three types of soil were 0.75, 0.80 and 0.76. No bidirectional chiral inversion of enantiopure carfentrazone-ethyl and carfentrazone enantiomers was observed in Jilin soil. As a result, R-(+)-carfentrazone-ethyl and S-(+)-carfentrazone in soil would be preferentially degraded, while S-(-)-carfentrazone-ethyl and R-(-)-carfentrazone were enriched. The results found in this paper could provide more scientific guidance for the risk assessments of carfentrazone-ethyl from a chiral perspective.

Transcriptomics analysis of the flowering regulatory genes involved in the herbicide resistance of Asia minor bluegrass (Polypogon fugax).

BACKGROUND: Asia minor bluegrass (Polypogon fugax, P. fugax), a weed that is both distributed across China and associated with winter crops, has evolved resistance to acetyl-CoA carboxylase (ACCase) herbicides, but the resistance mechanism remains unclear. The goal of this study was to analyze the transcriptome between resistant and sensitive populations of P. fugax at the flowering stage. RESULTS: Populations resistant and susceptible to clodinafop-propargyl showed distinct transcriptome profiles. A total of 206,041 unigenes were identified; 165,901 unique sequences were annotated using BLASTX alignment databases. Among them, 5904 unigenes were classified into 58 transcription factor families. Nine families were related to the regulation of plant growth and development and to stress responses. Twelve unigenes were differentially expressed between the clodinafop-propargyl-sensitive and clodinafop-propargyl-resistant populations at the early flowering stage; among those unigenes, three belonged to the ABI3VP1, BHLH, and GRAS families, while the remaining nine belonged to the MADS family. Compared with the clodinafop-propargyl-sensitive plants, the resistant plants exhibited different expression pattern of these 12 unigenes. CONCLUSION: This study identified differentially expressed unigenes related to ACCase-resistant P. fugax and thus provides a genomic resource for understanding the molecular basis of early flowering.