Bidirectional Uptake, Transfer, and Transport of Dextran-Based Nanoparticles in Plants for Multidimensional Enhancement of Pesticide Utilization.

The development of effective multifunctional nano-delivery approaches for pesticide absorption remains a challenge. Here, a dextran-based pesticide delivery system (MBD) is constructed to deliver tebuconazole for multidimensionally enhancing its effective utilization on tomato plants. Spherical MBD nanoparticles are obtained through two-step esterification of dextran, followed by tebuconazole loading using the Michael addition reaction. Confocal laser scanning microscopy shows that fluorescein isothiocyanate-labeled MBD nanoparticles can be bidirectionally transported in tomato plants and a modified quick, easy, cheap, effective, rugged, and safe-HPLC approach demonstrates the capacity to carry tebuconazole to plant tissues after 24 h of root uptake and foliar spray, respectively. Additionally, MBD nanoparticles could increase the retention of tebuconazole on tomato leaves by up to nearly 2.1 times compared with the tebuconazole technical material by measuring the tebuconazole content retained on the leaves. In vitro antifungal and pot experiments show that MBD nanoparticles improve the inhibitory effect of tebuconazole against botrytis cinerea by 58.4% and the protection against tomato gray molds by 74.9% compared with commercial suspensions. Furthermore, the MBD nanoparticles do not affect the healthy growth of tomato plants. These results underline the potential for the delivery system to provide a strategy for multidimensional enhancement of pesticide efficacy.

Dietborne Toxicity of Tebuconazole to a Benthic Crustacean, Heterocypris incongruens and Its Relative Contribution to the Overall Effects under Food-Water Equilibrium Partitioning.

Tebuconazole (TEB), a widely used and persistent pesticide, has garnered attention due to its frequent detection in sediments worldwide. This widespread occurrence has raised concerns about potential dietborne toxicity to benthic crustaceans, as they may ingest contaminated particles in their habitat. While bioaccumulation studies indicate the importance of TEB ingestion for benthic crustaceans, limited data exist on direct dietborne toxicity testing. This study investigated the diet-related toxicity of TEB by subjecting a benthic ostracod, Heterocypris incongruens, to a 6 day toxicity test under dietary and combined exposures. Subsequently, the importance of dietary exposure for TEB toxicity was uncovered, followed by quantification of relative dietborne toxicity contributions using a modified concentration-additive model. Results revealed that the dietary route was more toxicologically significant than the aqueous route in equilibrium. The dietborne lethal concentration (LC50) for TEB on H. incongruens was 200 (170-250) mg/kg, with an 80% relative dietborne toxicity contribution. To gain comprehensive insights into dietborne significance, toxicity data were collected from previous studies involving different pollutants to calculate relative contributions. Finally, the correlation between dietborne toxicity and the partitioning coefficient was analyzed to understand the pollutant behavior and its toxic impact when ingested through the diet.

Comparison of in vitro toxicity in HepG2 cells: Toxicological role of Tebuconazole-tert-butyl-hydroxy in exposure to the fungicide Tebuconazole.

Fungicides are often used prophylactically, to control fungal diseases. Although fungicides have been designed to control pests/fungi, they frequently share molecular targets with non-target species, including humans. Tebuconazole, a fungicide belonging to the class of triazoles, is widely employed, has moderate to high persistence in soil, and can be found in different environmental levels. This fungicide is metabolized to the main hydroxy-derived metabolite, Tebuconazole-tert-butyl-hydroxy (or hydroxytebuconazole). This study aims to unveil the action mechanism of Tebuconazole and the role played by its metabolite, Tebuconazole-tert-butyl-hydroxy (5-(4-Chlorophenyl)-2,2-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-1,3-pentanediol), within the expected spectrum of toxicity. In silico and in vitro analyses (MTT assay, cell cycle evaluation, annexin/PI assay, ROS accumulation assay, and mitochondrial membrane potential determination) were performed in HepG2 cells for 24 h and 48 h. Although in silico analysis suggested that both Tebuconazole and Tebuconazole-tert-butyl-hydroxy are potentially hepatotoxic, only Tebuconazole affected the tested cell line. Reduced MTT metabolism, and decreased mitochondrial membrane potential were the main findings. In conclusion, the action mechanism of Tebuconazole may be related to mitochondrial dysfunction. However, the findings of this study pointed out that Tebuconazole-tert-butyl-hydroxy does not play an important role in Tebuconazol toxicity. The study has generated new data that will help to understand how fungicides behave in the environment.

Toxicity assessment of a tebuconazole-based fungicide on the embryo-larval development of the common south American toad Rhinella arenarum.

Agrochemicals cause diverse effects on aquatic communities, and amphibian species are particularly threatened due the high susceptibility to contamination. Present study evaluates the toxicity of a widely used fungicide tebuconazole (Trigal®) by the assessment of mortality and developmental alterations at acute, subchronic, and chronic exposure during the embryo-larval development of the South American toad Rhinella arenarum. Also, the sensitivity of the different embryonic stages was evaluated with 24-h pulse exposure treatments. The results demonstrated that larvae were more sensitive than embryos at acute exposure (LC50-24 and 96 h = 74.62, 31.92 mg/L and 24.27, 16.81 mg/L for embryos and larvae, respectively). Nevertheless, embryos toxicity increased significantly achieving a sensitivity very similar to larvae at chronic exposure (LC50-168 and 504 h = 13.31, 4.35 mg/L and 14.47, 6.83 mg/L for embryos and larvae, respectively). Embryos exhibited several sublethal effects from 5 mg/L at 96 h onwards, such as delayed development, reduce body size, edemas, tail/axial flexures, weakness, and absence of movements. The teratogenic index at 96 h was 10.13, indicating the severe teratogenic potential of the fungicide. 24-h pulse exposure treatments showed an increased sensitivity in intermediate stages as S.11, S.18, S20, and S.23 (NOEC-96 h = 100, 200, 75, and 20 mg/L, respectively), while stage S.25 was the most sensitive to the fungicide (NOEC-96 h = 5 mg/L). About metamorphic process, tebuconazole caused an acceleration of metamorphosis at the lowest concentration (0.001 mg/L), but also an increase in mortality and in addition, significant differences in the weight in all treatments. The results obtained throughout this work indicate that tebuconazole cause several adverse effects in Rhinella arenarum embryo-larval development.

Comparative fitness of Monilinia fructicola isolates with multiple fungicide-resistant phenotypes.

This study characterized 52 isolates of Monilinia fructicola from peach and nectarine orchards for their multi-resistance patterns to thiophanate-methyl (TF), tebuconazole (TEB), and azoxystrobin (AZO) using in vitro sensitivity assays and molecular analysis. The radial growth of M. fructicola isolates was measured on media amended with a single discriminatory dose of 1 µg/ml for TF and AZO and 0.3 µg/ml for TEB. Cyt b, CYP51, and ß-tubulin were tested for point mutations that confer resistance to quinone outside inhibitors (QoIs), demethylation inhibitors (DMIs), and methyl benzimidazole carbamates (MBCs), respectively. Eight phenotypes were identified including isolates with single, double, and triple in vitro resistance to QoI, MBC, and DMI fungicides. All resistant phenotypes to TF and TEB presented the H6Y mutation in ß-tubulin and the G641S mutation in CYP51. None of the point mutations typically linked to QoI resistance were present in the Monilinia isolates examined. Moreover, fitness of the M. fructicola phenotypes was examined in vitro and detached fruit assays. Phenotypes with single-resistance displayed equal fitness in in vitro and fruit assays compared to the wild-type. In contrast, the dual and triple-resistance phenotypes suffered fitness penalties based on osmotic sensitivity and aggressiveness on peach fruit. In this study, multiple resistance to MBC, DMI, and QoI fungicide groups was confirmed in M. fructicola. Results suggest that Monilinia populations with multiple resistance phenotypes are likely to be less competitive in the field than those with single resistance, thereby impeding their establishment over time and facilitating disease management.

Tebuconazole Induces Mouse Fetal Testes Damage via ROS Generation in an Organ Culture Method.

The fungicide tebuconazole (TEB) poses risks to human and animal health via various exposure routes. It induces toxicity in multiple organs and disrupts reproductive health by affecting steroid hormone synthesis and fetal development. In this study, we investigated the impact of TEB on fetal testes using in vitro models, focusing on germ, Sertoli, and Leydig cells, and explored the mechanisms underlying cellular damage. The results revealed significant damage to germ cells and disruption of Leydig cell development. TEB exposure led to a decrease in germ cell numbers, as indicated by histological and immunostaining analyses. TEB induced the up- and down-regulation of the expression of fetal and adult Leydig cell markers, respectively. Additionally, TEB-treated fetal testes exhibited increased expression of oxidative-stress-related genes and proteins. However, co-treatment with the antioxidant N-acetylcysteine mitigated TEB-induced germ cell damage and prevented abnormal Leydig cell development. These findings suggest that administration of antioxidants can prevent the intratesticular damage typically caused by TEB exposure.

Waterborne Tebuconazole Exposure Induces Male-Biased Sex Differentiation in Zebrafish (Danio rerio) Larvae via Aromatase Inhibition.

Tebuconazole is a widely used fungicide for various crops that targets sterol 14-α-demethylase (CYP51) in fungi. However, attention has shifted to aromatase (CYP19) due to limited research indicating its reproductive impact on aquatic organisms. Herein, zebrafish were exposed to 0.5 mg/L tebuconazole at different developmental stages. The proportion of males increased significantly after long-term exposure during the sex differentiation phase (0-60, 5-60, and 19-60 days postfertilization (dpf)). Testosterone levels increased and 17ß-estradiol and cyp19a1a expression levels decreased during the 5-60 dpf exposure, while the sex ratio was equally distributed on coexposure with 50 ng/L 17ß-estradiol. Chemically activated luciferase gene expression bioassays determined that the male-biased sex differentiation was not caused by tebuconazole directly binding to sex hormone receptors. Protein expression and phosphorylation levels were specifically altered in the vascular endothelial growth factor signaling pathway despite excluding the possibility of tebuconazole directly interacting with kinases. Aromatase was selected for potential target analysis. Molecular docking and aromatase activity assays demonstrated the interactions between tebuconazole and aromatase, highlighting that tebuconazole poses a threat to fish populations by inducing a gender imbalance.

Metabolic pathway of tebuconazole by soil fungus Cunninghamella elegans ATCC36112.

Tebuconazole is the most widely used fungicide in agriculture. Due to its long half-life, tebuconazole residues can be found in the environment media such as in soil and water bodies. Here, the metabolic pathway of tebuconazole was studied in Cunninghamella elegans (C. elegans). Approximately 98% of tebuconazole was degraded within 7 days, accompanied by the accumulation of five metabolites. The structures of the metabolites were completely or tentatively identified by gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). To identify representative oxidative enzymes that may be involved in the metabolic process, treatment with piperonyl butoxide (PB) and methimazole (MZ) was performed. PB had a strong inhibitory effect on the metabolic reactions, while MZ had a weak inhibitory effect. The results suggest that cytochrome P450 (CYP) and flavin-dependent monooxygenase are involved in the metabolism of tebuconazole. Based on the results, we propose a metabolic pathway for the fungal metabolism of tebuconazole. Data are of interest to gain insight into the toxicological effects of tebuconazole and for tebuconazole bioremediation.

Baseline Sensitivity and Resistance Mechanism of Colletotrichum Isolates on Tea-Oil Trees of China to Tebuconazole.

Colletotrichum fungi could cause anthracnose, a destructive disease in tea-oil trees. The sterol demethylation inhibitor (DMI) tebuconazole has been widely used in controlling plant diseases for many years. However, the baseline sensitivity of Colletotrichum isolates on tea-oil trees to tebuconazole has not been determined. In this study, the sensitivity to tebuconazole of 117 Colletotrichum isolates from tea-oil trees of seven provinces in southern China was tested. The mean effective concentration resulted in 50% mycelial growth inhibition (EC50), 0.7625 µg/ml. The EC50 values of 100 isolates (83%) were lower than 1 µg/ml, and those of 20 isolates (17%) were higher than 1 µg/ml, which implied that resistance has already occurred in Colletotrichum isolates on tea-oil trees. The EC50 values of the most resistant and sensitive isolates (named Ca-R and Cc-S1, respectively) were 1.8848 and 0.1561 µg/ml, respectively. The resistance mechanism was also investigated in this study. A gene replacement experiment indicated that the CYP51A/B gene of resistant isolates Ca-R and Cf-R1 cannot confer Cc-S1 full resistance to DMI fungicides, although three single point mutants, Cc-S1CYP51A-T306A and Cc-S1CYP51A-R478K, exhibited decreased sensitivity to DMI fungicides. This result suggested that resistance of Colletotrichum isolates was partly caused by mutations in CYP51A. Moreover, the expression level of CYP51A/B was almost identical among Ca-R, Cf-R1, Cc-S1, and Cc-S1CYP51A point mutants, which indicated that the resistance was irrelevant to the expression level of CYP51A, and other nontarget-based resistance mechanisms may exist. Our results could help to guide the application of DMI fungicides and be useful for investigating the mechanism of resistance.

Improvement of Akanthomyces lecanii resistance to tebuconazole through UV-C radiation and selective pressure on microbial evolution and growth arenas.

Tebuconazole (TEB) is a fungicide widely used in agriculture; however, its constant application has increased the emergence of resistant plant pathogenic fungal strains and reduced the effectiveness of fungi as biological control agents; for instance, the entomopathogenic and hyperparasitic fungus Akanthomyces lecanii, suitable for simultaneous biological control of insect pest and plant pathogenic fungi, is highly sensitive to fungicides. We carried out the induction of resistance to TEB in two wild type strains of A. lecanii by UV radiation and selective pressure in increasing fungicide gradients using a modified Microbial Evolution and Growth Arena (MEGA), to produce A. lecanii strains that can be used as biological control agent in the presence of tebuconazole. Nine UV-induced and three naturally adapted A. lecanii strains were resistant to TEB at the agriculturally recommended dose, and three irradiated strains were resistant to TEB concentration ten times higher; moreover, growth, sporulation rates, production of hydrolytic enzymes, and virulence against the hemipteran Coccus viridis, a major pest of coffee crops, were not affected in the TEB-resistant strains. These A. lecanii TEB-resistant strains would have a greater opportunity to develop and to establish themselves in fields where the fungicide is present and can be used in a combined biological-chemical strategy to improve insect and plant pathogenic fungal control in agriculture. Also, the selective pressure through modified MEGA plate methodology can be used for the adaptation of entomopathogenic filamentous fungi to withstand other chemical or abiotic stresses that limits its effectiveness for pest control.

Antifungal triazoles affect key non-target metabolic pathways in Solanum lycopersicum L. plants.

Several 1,2,4-triazoles are widely used as systemic fungicides in agriculture because they inhibit fungal 14ɑ-demethylase. However, they can also act on many non-target plant enzymes, thereby affecting phytohormonal balance, free amino acid content, and adaptation to stress. In this study, tomato plants (Solanum lycopersicum L. var. 'Cherrola') were exposed to penconazole, tebuconazole, or their combination, either by foliar spraying or soil drenching, every week, as an ecotoxicological model. All triazole-exposed plants showed a higher content (1.7-8.8 ×) of total free amino acids than the control, especially free glutamine and asparagine were increased most likely in relation to the increase in active cytokinin metabolites 15 days after the first application. Conversely, the Trp content decreased in comparison with control (0.2-0.7 ×), suggesting depletion by auxin biosynthesis. Both triazole application methods slightly affected the antioxidant system (antioxidant enzyme activity, antioxidant capacity, and phenolic content) in tomato leaves. These results indicated that the tomato plants adapted to triazoles over time. Therefore, increasing the abscisic and chlorogenic acid content in triazole-exposed plants may promote resistance to abiotic stress.

Recommended rates of azoxystrobin and tebuconazole seem to be environmentally safe but ineffective against target fungi.

The use of fungicides in agriculture has been playing a role in the enhancement of agricultural yields through the control of pathogens causing serious diseases in crops. Still, adverse environmental and human health effects resulting from its application have been reported. In this study, the possibility of readjusting the formulation of a commercial product combining azoxystrobin and tebuconazole (active ingredients - AIs; Custodia®) towards environmentally safer alternative(s) was investigated. Specifically, the sensitivity of non-target aquatic communities to each AI was first evaluated by applying the Species Sensitivity Distributions (SSDs) approach. Then, mixtures of these AIs were tested in a non-target organism (Raphidocelis subcapitata) denoting sensitivity to both AIs as assessed from SSDs. The resulting data supported the design of the last stage of this study, where mixtures of those AIs at equivalent vs. alternative ratios and rates as in the commercial formulation were tested against two target fungal species: Pyrenophora teres CBS 123929 and Rhynchosporium secalis CBS 110524. The comparison between the sensitivity of non-target aquatic species and the corresponding efficacy towards target fungi revealed that currently applied mixture and rates of these AIs are generally environmentally safe (antagonistic interaction; concentrations below the EC1 for R. subcapitata and generally below the HC5 for aquatic non-target communities), but ineffective against target organisms (maximum levels of inhibition of 70 and 50% in P. teres CBS 123929 and R. secalis CBS 110524, respectively). Results additionally suggest a potentiation of the effects of the AIs by the other formulants added to the commercial product at tested rates. Overall, this study corroborates that commercial products can be optimized during design stages based on a systematic ecotoxicological testing for ingredient interactions and actual efficacy against targets. This could be a valuable pathway to reduce environmental contamination during transition to a more sustainable agricultural production.

Study of the Methylation of Bovine GSTP1 Gene under the Influence of Pesticide Mospilan 20SP Alone and in Combination with Pesticide Orius 25EW.

DNA methylation, one of the most studied epigenetic mechanisms, when present in the promoter region of genes, causes inhibition of gene expression, and conversely, hypomethylation of these regions enables gene expression. DNA methylation is susceptible to nutritional and environmental influences, and undesirable alterations in methylation patterns manifested in changes in the expression of relevant genes can lead to pathological consequences. In the present work, we studied the methylation status of the bovine GSTP1 gene under the influence of pesticide Mospilan 20SP alone and in combination with pesticide Orius 25EW in in vitro proliferating bovine lymphocytes. We employed methylation-specific PCR, and when studying the effect of pesticide combinations, we also used its real-time version followed by a melting procedure. Our results showed that Mospilan 20SP alone at 5, 25, 50, and 100 µg.ml-1 and 5, 10, 25, and 50 µg.ml-1 for the last 4 and 24 hours of culture with in vitro proliferating bovine lymphocytes, respectively, did not induce methylation of the bovine GSTP1 gene. The same results were revealed when studying the effect of the combination of the pesticides added to the lymphocyte cultures for the last 24 hours of cultivation in the following amounts: 1.25, 2.5, 5, 10, and 25 µg.ml-1 of Mospilan 20SP and 1.5, 3, 6, 15, and 30 µg.ml-1 of Orius 25EW. We have also revealed that the less laborious real-time MSP followed by a melting procedure may replace MSP for studying the methylation status of the GSTP1 gene.

Residues of sulfoxaflor and its metabolites in floral and extrafloral nectar from Hibiscus rosa-sinensis L. (Malvaceae) with or without co-application of tebuconazole.

Systemic pesticide exposure through nectar is a growing global concern linked to loss of insect diversity, especially pollinators. The insecticide sulfoxaflor and the fungicide tebuconazole are currently widely used systemic pesticides which are toxic to certain pollinators. However, their metabolisms in floral or extrafloral nectar under different application methods have not yet been well studied. Hibiscus rosa-sinensis was exposed to sulfoxaflor and tebuconazole via soil drenching and foliar spraying. Sulfoxaflor, tebuconazole, and their main metabolites in floral and extrafloral nectar, soil, and leaves were identified and quantified using liquid chromatography coupled with triple quadrupole mass spectrometry (LC-QqQ MS). The chemical compositions of unexposed and contaminated H. rosa-sinensis floral nectar or extrafloral nectar were compared using regular biochemical methods. The activities of two pesticide detoxifying enzymes, glutathione-s-transferase and nitrile hydratase, in H. rosa-sinensis nectar were examined using LC-MS and spectrophotometry. The floral nectar proteome of H. rosa-sinensis was analysed using high-resolution orbitrap-based MS/MS analysis to screen for sulfoxaflor and tebuconazole detoxifying enzymes. H. rosa-sinensis can absorb sulfoxaflor and tebuconazole through its roots or leaf surfaces and secrete them into floral nectar and extrafloral nectar. Both sulfoxaflor and tebuconazole and their major metabolites were present at higher concentrations in extrafloral nectar than in floral nectar. X11719474 was the dominant metabolite of sulfoxaflor in the nectars we studied. Compared with soil application, more sulfoxaflor and tebuconazole remained in their original forms in floral nectar and extrafloral nectar after foliar application. Sulfoxaflor and tebuconazole exposure did not modify the chemical composition of floral or extrafloral nectar. No active components, including proteins in the nectar, were detected to be able to detoxify sulfoxaflor.

The calcium-calcineurin and high-osmolarity glycerol pathways co-regulate tebuconazole sensitivity and pathogenicity in Fusarium graminearum.

The calcium-calcineurin and high-osmolarity glycerol (HOG) pathways play crucial roles in fungal development, pathogenicity, and in responses to various environmental stresses. However, interaction of these pathways in regulating fungicide sensitivity remains largely unknown in phytopathogenic fungi. In this study, we investigated the function of the calcium-calcineurin signalling pathway in Fusarium graminearum, the causal agent of Fusarium head blight. Inhibitors of Ca2+ and calcineurin enhanced antifungal activity of tebuconazole (an azole fungicide) against F. graminearum. Deletion of the putative downstream transcription factor FgCrz1 resulted in significantly increased sensitivity of F. graminearum to tebuconazole. FgCrz1-GFP was translocated to the nucleus upon tebuconazole treatment in a calcineurin-dependent manner. In addition, deletion of FgCrz1 increased the phosphorylation of FgHog1 in response to tebuconazole. Moreover, the calcium-calcineurin and HOG signalling pathways exhibited synergistic effect in regulating pathogenicity and sensitivity of F. graminearum to tebuconazole and multiple other stresses. RNA-seq data revealed that FgCrz1 regulated expression of a set of non-CYP51 genes that are associated with tebuconazole sensitivity, including multidrug transporters, membrane lipid biosynthesis and metabolism, and cell wall organization. Our findings demonstrate that the calcium-calcineurin and HOG pathways act coordinately to orchestrate tebuconazole sensitivity and pathogenicity in F. graminearum, which may provide novel insights in management of Fusarium disease.

Dispersive magnetic solid phase extraction of triazole fungicides based on polybenzidine/magnetic nanoparticles in environmental samples.

A polybenzidine-modified Fe3O4@SiO2 nanocomposite was successfully synthesized through a chemical oxidation method and employed as a novel sorbent in dispersive magnetic solid phase extraction (DMSPE) for the preconcentration and determination of three triazole fungicides (TFs), namely diniconazole, tebuconazole, and triticonazole in river water, rice paddy soil, and grape samples. The synthesis method involved a polybenzidine self-assembly coating on Fe3O4@SiO2 magnetic composite. Characterization techniques such as FT-IR, XRD, FESEM, EDX, and VSM were used to confirm the correctness of the synthesized nano-sorbent. The target TFs were determined in actual samples using the synthesized nanocomposite sorbent in combination with gas chromatography-flame ionization detection (FID). Several variables were carefully optimized , including the sample pH, sorbent dosage, extraction time, ionic strength, and desorption condition (solvent type, volume, and time). Under the optimized experimental conditions, the method exhibited linearity in the concentration range 5-1000 ng mL-1 for triticonazole and 2-1000 ng mL-1 for diniconazole and tebuconazole. The limits of detection (LOD) for the three TFs were in the range 0.6-1.5 ng mL-1. The method demonstrated acceptable precision with intra-day and inter-day relative standard deviation (RSD) values of less than 6.5%. The enrichment factors ranged from 248 to 254. Finally, the method applicability was evaluated by determining TFs in river water, rice paddy soil, and grape samples with recoveries in the range 90.5-106, indicating that the matrix effect was negligible in the proposed DMSPE procedure.

Efficient Adsorption of Tebuconazole in Aqueous Solution by Calcium Modified Water Hyacinth-Based Biochar: Adsorption Kinetics, Mechanism, and Feasibility.

The application of fungicides (such as tebuconazole) can impose harmful impacts on the ecosystem and humans. In this study, a new calcium modified water hyacinth-based biochar (WHCBC) was prepared and its effectiveness for removing tebuconazole (TE) via adsorption from water was tested. The results showed that Ca was loaded chemically (CaC2O4) onto the surface of WHCBC. The adsorption capacity of the modified biochar increased by 2.5 times in comparison to that of the unmodified water hyacinth biochar. The enhanced adsorption was attributed to the improved chemical adsorption capacity of the biochar through calcium modification. The adsorption data were better fitted to the pseudo-second-order kinetics and the Langmuir isotherm model, indicating that the adsorption process was dominated by monolayer adsorption. It was found that liquid film diffusion was the main rate-limiting step in the adsorption process. The maximum adsorption capacity of WHCBC was 40.5 mg/g for TE. The results indicate that the absorption mechanisms involved surface complexation, hydrogen bonding, and π-π interactions. The inhibitory rate of Cu2+ and Ca2+ on the adsorption of TE by WHCBC were at 4.05-22.8%. In contrast, the presence of other coexisting cations (Cr6+, K+, Mg2+, Pb2+), as well as natural organic matter (humic acid), could promote the adsorption of TE by 4.45-20.9%. In addition, the regeneration rate of WHCBC was able to reach up to 83.3% after five regeneration cycles by desorption stirring with 0.2 mol/L HCl (t = 360 min). The results suggest that WHCBC has a potential in application for removing TE from water.

Safe Application of 75% Trifloxystrobin-Tebuconazole as Water-Dispersible Granules in Paddy Based on Residue and Dietary Risk Assessment.

The present study describes the development of a highly effective approach for determining the residue distribution and dissipation of trifloxystrobin and tebuconazole, and their risk assessment in brown rice, husk, straw, and grain using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The current study provides considerable novel information regarding the safe utilization of a mixture of trifloxystrobin and tebuconazole in paddy production. The samples demonstrated a range of mean recoveries between 72% and 86%, with a 1.1-9.2% relative standard deviation (RSD). The limits of quantification (LOQ) and half-lives (t1/2) for brown rice, husk, straw, and grain were, respectively, established to be 0.001-0.01 mg/kg and 4.1-7.7 days. The concentrations of terminal residues in the brown rice, husk, straw, and grain were, respectively, found to be 0.02-0.05, 0.03-0.11, 0.02-0.07, and 0.02-0.05 mg/kg after being treated twice at 168.75 g a.i./ha with 21 and 28 days of pre-harvest intervals (PHIs). Trifloxystrobin and tebuconazole presented a non-negligible chronic risk to human subjects, as evidenced by a risk quotient (RQ) value of less than 1.

Status of Fungicide Resistance and Physiological Characterization of Tebuconazole Resistance in Rhizocotonia solani in Sichuan Province, China.

The resistance prevalence of chemical fungicides has caused increasingly serious agro-ecological environmental problems. However, there are few previous reports about resistance to succinate dehydrogenase (SDHI) or sterol demethylation inhibitor (DMI) in Rhizoctonia solani, one of the main agro-diseases. In this study, the fungicide resistance of 122 R. solani isolates in Sichuan Province was monitored by the mycelial growth rate method. Results showed that all isolates were susceptible to hexaconazole and most isolates were susceptible to thifluzamide, except for the field isolate MSRS-2-7 due to a moderate resistance to thifluzamide (16.43-fold resistance ratio, RR), compared to the sensitivity baseline of thifluzamide (0.042 µg/mL EC50 values). On the contrary, many isolates showed moderate or high resistance to tebuconazole (10.59- to 60.78-fold RR), reaching EC50 values of 0.54~3.10 µg/mL, especially for a highly resistant isolate LZHJ-1-8 displaying moderate resistance to epoxiconazole (35.40-fold RR due to a 3.54 µg/mL EC50 value). The fitness determination found that the tebuconazole-resistant isolates showed higher fitness cost with these characteristics, including a lower growth rate, higher relative electric conductivity, an increased ability to tolerate tebuconazole, and high osmotic pressure. Four new mutations of cytochrome P450 sterol 14α-demethylase (CYP51), namely, S94A, N406S, H793R, and L750P, which is the target for DMI fungicides, was found in the tebuconazole-resistant isolates. Furthermore, the lowest binding energy with tebuconazole was also found in the LZHJ-1-8 isolate possessing all the mutations through analyses with Discovery Studio software. Therefore, these new mutation sites of CYP51 may be linked to the resistance against tebuconazole, and its application for controlling R. solani should be restricted in some areas.

The very long-chain fatty acid elongase FgElo2 governs tebuconazole sensitivity and virulence in Fusarium graminearum.

Very long-chain fatty acids (VLCFAs), the precursors for the synthesis of sphingolipids (SLs), play pivotal roles in the development and stress response in eukaryotes. In Saccharomyces cerevisiae, VLCFAs are synthesized in the endoplasmic reticulum (ER) through a four-step elongation cycle. However, the functions of VLCFA elongases in phytopathogenic fungi remain largely unexplored. Here, we identified a single copy of the VLCFA elongase gene FgELO2 in Fusarium graminearum that causes Fusarium head blight worldwide. FgElo2 localized to ER membrane, and deletion mutant of FgELO2 exhibited serious defects in vegetative growth and conidiation. Importantly, ΔFgElo2 led to ergosterol content reduction and disrupted the ER-localization of 14-α-demethylase FgCyp51s, indicating that the scarce of SLs reduced ergosterol, which ultimately elevated the sensitivity of ΔFgElo2 to tebuconazole. Fluorescent microscopic examination suggested that FgElo2 was degraded upon cell membrane stress. ΔFgElo2 showed decreased phosphorylation of high osmolarity glycerol (HOG) pathway and subsequently exhibited remarkable sensitivity to osmotic stress. In addition, fungal virulence was dramatically reduced in ΔFgElo2 via inhibiting deoxynivalenol production and formation of infection structures. Together, this study demonstrates that the VLCFA elongase FgElo2 modulates fungal development, tebuconazole sensitivity, stress responses and virulence, which may advance our understanding of pathogen-host interactions mediated by VLCFAs.