Degradation Of Azoxystrobin Research Articles

Degradation of azoxystrobin, methoxyfenozide, and propyzamide by ultrasound treatment.

Ultrasound as a green and efficient process gains special attention in wastewater treatment. The ultrasound-assisted degradation of azoxystrobin, methoxyfenozide, and propyzamide as widely used pesticides for vine treatment was investigated. A wide range of ultrasonic power (40 to 140 W) and a single frequency (20 kHz) were applied. Degradation experiments were carried out according to the parameters set by a central composite design (CCD) under response surface methodology (RSM) via JMP software. The treatment efficiency was quantified using degradation rates and hydrogen peroxide (H2O2) measurements. Results indicated that the pesticide's degradation was negligible at 40 W but by increasing the power setting from 80 to 140 W, the degradation rate constants of azoxystrobin, methoxyfenozide, and propyzamide increased from 3.6 × 10-2 min-1 to 0.2 min-1, from 6.1 × 10-2 min-1 to 0.3 min-1, and from 3.1 × 10-2 min-1 to 0.1 min-1, respectively. The hydrogen peroxide (H2O2) measurements confirmed this trend. Besides, electric energy per order of pollutant removal (EE/O) was also evaluated for the same treatment duration and results revealed that treatment conditions of 20 kHz and 140 W were the less energy-guzzling. Finally, profiles obtained with RSM illustrated linear degradation kinetics for azoxystrobin and propyzamide. Indeed, treatment efficiency increased when increasing both studied parameters. However, both linear and quadratic degradation kinetics occurred for methoxyfenozide degradation indicating a parameter threshold beyond which the trend is reversed. Overall, this study confirms the effectiveness of ultrasound for the degradation of pesticides in aqueous medium.

A powerful helper of azoxystrobin degradation-the unique mechanism of UGT72E2 promoting environmental degradation of azoxystrobin.

In recent years, environmental pollutants such as pesticide residues have become one of the severe public problems that endanger the ecological environment and affect human health. The development of biotechnology to rapidly and efficiently degrade pesticides is essential to reduce their environmental risks. Azoxystrobin (AZ) is representative of the most widely used agricultural fungicide in the world. A large number of studies have shown that AZ has toxic effects on non-target organisms such as fish, algae, earthworms, etc., which may pose a potential threat to the environmental ecosystem. Therefore, it is particularly important to develop new AZ phytoremediation methods. Based on the constructed Arabidopsis UGT72E2 knockout (KO) and overexpression (OE) lines, this study found that overexpression of UGT72E2 in Arabidopsis can enhance resistance to exogenous AZ stress and maintain a relatively stable physiological state while enhancing the metabolic degradation of AZ. Correspondingly, knockout mutants showed the opposite results. The results showed that the AZ glycosylation and malonyl glycosylation products produced by UGT72E2 overexpression lines increased by 10%~20% compared with normal lines, and increased by 7%~47% compared with gene knockout plants, and exhibited lower phytotoxicity. In summary, our findings highlight the critical role of UGT72E2 overexpression in constructing new varieties of phytoremediation and may provide new ideas for reducing the indirect or direct risks of pesticides or other environmental pollutants to non-target organisms and improving biological and environmental resilience.

Diverse bacteria colonizing leaves and the rhizosphere of lettuce degrade azoxystrobin

Concerns about the possible effects of pesticide residues on both the environment and human health have increased worldwide. Bioremediation by the use of microorganisms to degrade or remove these residues has emerged as a powerful technology. However, the knowledge about the potential of different microorganisms for pesticide degradation is limited. This study focused on the isolation and characterisation of bacterial strains with the potential to degrade the active fungicide ingredient azoxystrobin. Potential degrading bacteria were tested in vitro and in the greenhouse, and the genomes of the best degrading strains were sequenced and analysed.We identified and characterised 59 unique bacterial strains, which were further tested in vitro and in greenhouse trials for their degradation activity. The best degraders from a foliar application trial in the greenhouse were identified as Bacillus subtilis strain MK101, Pseudomonas kermanshahensis strain MK113 and Rhodococcus fascians strain MK144 and analysed by whole genome sequencing. Genome analysis revealed that these three bacterial strains encode several genes predicted to be involved in the degradation of pesticides e.g., benC, pcaG, pcaH, however we could not find any specific gene previously reported to be involved in azoxystrobin degradation e.g., strH. Genome analysis pinpointed to some potential activities involved in plant growth promotion.

Characterization of the responses of soil micro-organisms to azoxystrobin and the residue dynamics of azoxystrobin in wheat–corn rotation fields over two years

Azoxystrobin, a high-efficiency and broad-spectrum strobilurin fungicide, has been widely used in global agricultural production. However, the effects of azoxystrobin on soil micro-organisms have scarcely been studied, and relevant experiments are usually conducted under laboratory conditions using active ingredient. Therefore, the effects of azoxystrobin on soil micro-organisms when applied to actual farmland are unknown. We sought to address this knowledge gap in this study, where we studied the effects of azoxystrobin on soil micro-organisms in a wheat–corn rotation field over two years. The results indicate that after two years of azoxystrobin application the activities of soil enzymes were inhibited, and the abundance of functional genes related to the nitrogen and carbon cycle were inhibited, which change the abundance of soil microbial bacteria of genera. As a consequence, the soil nitrogen and carbon cycles were disturbed. In addition, azoxystrobin inhibited the abundance of functional bacteria related to organic pollutant degradation and soil metabolism, where the rate of azoxystrobin degradation diminished over time. Moreover, azoxystrobin significantly inhibited the soil-culturable microbial population. The integrated biomarker response (IBR) indicated that the soil-culturable microbial population can be used as a sensitive indicator of the effect of azoxystrobin on soil micro-organisms. The final levels of azoxystrobin residues measured in grains were less than 0.004 mg/kg, lower than the maximum residue limits in European Union and China. The results of this study provide a basis for suggestions regarding the appropriate use of azoxystrobin in addition to support for elucidating the interaction between biological macromolecules and pollutants.

Supermagnetic Mn-substituted ZnFe2O4 with AB-site hybridization for the ultra-effective catalytic degradation of azoxystrobin

Magnetic Zn0.25Mn0.75Fe2O4 was applied to the degradation of azoxystrobin in a Fenton-like system, and the performance was enhanced via crystal structure control.

The Effect of Mass Transfer Rate-Time in Bubbles on Removal of Azoxystrobin in Water by Micro-Sized Jet Array Discharge

In this work, the azoxystrobin removal in water by using a micro-size discharge array was investigated, and the removal efficiency can reach as high as 98.1% after 9 min plasma treatment as well as the energy utilization being only 0.73 g/(kW·h). Based on the relationship between the generation of gas bubbles and parameters of gas-liquid discharge, it was found that the variation of applied voltage, gas flow rate and initial solution temperature could cause particle number change, mass transfer rate change and the mass transfer time change, which significantly affected the practical applications at last. The experimental results indicated that when gas flow rate was 0.7 SLM (Standard Liter per Minute) and the initial solution temperature was 297 K with the applied voltage of 8 kV and discharge frequency of 6 kHz, the removal efficiency of azoxystrobin achieved maximum. Based on the analysis results of liquid mass spectrometry, the removal pathways of azoxystrobin were supposed by the decomposed by-products. Toxicity tests indicated that the decomposed products were safe and non-toxic. So, this study may reveal an azoxystrobin degradation mechanism and provide a safe, reliable and effective way for azoxystrobin degradation.

Azoxystrobin and imidacloprid degradation in biobed setup under laboratory conditions

ABSTRACT Biobeds are an important tool to check point source of pesticide contamination and treat on-farm generated pesticide waste. The present study reports retention and degradation of azoxystrobin and imidacloprid in the rice straw – compost (RS+C) and corn cob – compost (CC+C) biobeds. Azoxystrobin (10,000 µg) + imidacloprid (10,000 µg) in 100 mL water were co-applied twice at an interval of 45 days. Both biobeds were effective in retaining high amounts of azoxystrobin and imidacloprid, and no pesticide was detected in the leachate. After 45 days of Ist application, no imidacloprid was detected in the surface layer (3–4 cm) of both the biobeds, while 8.24 and 5.36 µg g−1of azoxystrobin were detected in the RS+C and CC+C biomixtures, respectively. After 30 days of IInd application, destructive sampling suggested that imidacloprid was completely degraded in both the biobeds, while only 81.5% and 68.1% of azoxystrobin degradation were observed in the RS+C and CC+C biobeds, respectively. Imidacloprid was mainly restricted to the surface layer in both biobeds. The RS+C biobed was better than the CC+C in degrading azoxystrobin and was attributed to its higher microbial biomass carbon content. The low-cost biomixtures made of easily available materials have the potential of degrading azoxystrobin and imidacloprid containing rinsate.

Azoxystrobin amine: A novel azoxystrobin degradation product from Bacillus licheniformis strain TAB7

Azoxystrobin (AZ) is a broad-spectrum synthetic fungicide widely used in agriculture globally. However, there are concerns about its fate and effects in the environment. It is reportedly transformed into azoxystrobin acid as a major metabolite by environmental microorganisms. Bacillus licheniformis strain TAB7 is used as a compost deodorant in commercial compost and has been found to degrade some phenolic and agrochemicals compounds. In this article, we report its ability to degrade azoxystrobin by novel degradation pathway. Biotransformation analysis followed by identification by electrospray ionization-mass spectrometry (MS), high-resolution MS, and nuclear magnetic resonance spectroscopy identified methyl (E)-3-amino-2-(2-((6-(2-cyanophenoxy)pyrimidin-4-yl)oxy)phenyl)acrylate, or (E)-azoxystrobin amine in short, and (Z) isomers of AZ and azoxystrobin amine as the metabolites of (E)-AZ by TAB7. Bioassay testing using Magnaporthe oryzae showed that although 40 μg/mL of (E)-AZ inhibited 59.5 ± 3.5% of the electron transfer activity between mitochondrial Complexes I and III in M. oryzae, the same concentration of (E)-azoxystrobin amine inhibited only 36.7 ± 15.1% of the activity, and a concentration of 80 μg/mL was needed for an inhibition rate of 56.8 ± 7.4%, suggesting that (E)-azoxystrobin amine is less toxic than the parent compound. To our knowledge, this is the first study identifying azoxystrobin amine as a less-toxic metabolite from bacterial AZ degradation and reporting on the enzymatic isomerization of (E)-AZ to (Z)-AZ, to some extent, by TAB7. Although the fate of AZ in the soil microcosm supplemented with TAB7 will be needed, our findings broaden our knowledge of possible AZ biotransformation products.

Kinetics and New Mechanism of Azoxystrobin Biodegradation by an Ochrobactrum anthropi Strain SH14.

Azoxystrobin is one of the most popular strobilurin fungicides, widely used in agricultural fields for decades.Extensive use of azoxystrobin poses a major threat to ecosystems. However, little is known about the kinetics and mechanism of azoxystrobin biodegradation. The present study reports a newly isolated bacterial strain, Ochrobactrum anthropi SH14, utilizing azoxystrobin as a sole carbon source, was isolated from contaminated soils. Strain SH14 degraded 86.3% of azoxystrobin (50 μg·mL−1) in a mineral salt medium within five days. Maximum specific degradation rate (qmax), half-saturation constant (Ks), and inhibition constant (Ki) were noted as 0.6122 d−1, 6.8291 μg·mL−1, and 188.4680 μg·mL−1, respectively.Conditions for strain SH14 based azoxystrobin degradation were optimized by response surface methodology. Optimum degradation was determined to be 30.2 °C, pH 7.9, and 1.1 × 107 CFU·mL−1 of inoculum. Strain SH14 degraded azoxystrobin via a novel metabolic pathway with the formation of N-(4,6-dimethoxypyrimidin-2-yl)-acetamide,2-amino-4-(4-chlorophenyl)-3-cyano-5,6-dimethyl-pyridine, and 3-quinolinecarboxylic acid,6,8-difluoro-4-hydroxy-ethyl ester as the main intermediate products, which were further transformed without any persistent accumulative product. This is the first report of azoxystrobin degradation pathway in a microorganism. Strain SH14 also degraded other strobilurin fungicides, including kresoxim-methyl (89.4%), pyraclostrobin (88.5%), trifloxystrobin (78.7%), picoxystrobin (76.6%), and fluoxastrobin (57.2%) by following first-order kinetic model. Bioaugmentation of azoxystrobin-contaminated soils with strain SH14 remarkably enhanced the degradation of azoxystrobin, and its half-life was substantially reduced by 95.7 and 65.6 days in sterile and non-sterile soils, respectively, in comparison with the controls without strain SH14. The study presents O. anthropi SH14 for enhanced biodegradation of azoxystrobin and elaborates on the metabolic pathways to eliminate its residual toxicity from the environment.

Dynamic distribution of azoxystrobin residues in strawberry (Fragaria x ananassa Duchesne) using liquid chromatography tandem mass spectrometry: Putative evaluation of dietary intake

ABSTRACT A simple, rapid and environmentally compatible method involving quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction technique for simultaneous detection of azoxystrobin residues in strawberry was optimised and validated. Liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS) was also used for quantitative and confirmatory analysis of azoxystrobin residues in strawberry. Recoveries ranged between 96% and 111% and repeatability (expressed as percentage relative standard deviation, % RSD) typically <11% has been well achieved. The dissipation pattern of azoxystrobin in different treatments level, based on the most critical field use patterns was reported utilising the method developed in this study. The results revealed that the degradation of azoxystrobin in strawberry followed first-order kinetics (R2 > 0.974) with estimated half-life value of 8.45 days. Considering the terminal residues and the maximum residue limit (MRL, 10 mg kg−1) in strawberry, and based on this study, it is safe to harvest strawberry 3 days after applying azoxystrobin even at rated higher the recommended one with exaggerated, suggesting that the use of this compound is safe for humans. The results could provide a guidance to fully evaluate the risks of azoxystrobin to consumers.

Parameters affecting azoxystrobin and imidacloprid degradation in biobed substrates in the North Indian tropical environment

This study reports degradation of azoxystrobin (AZOXY) and imidacloprid (IMIDA) in the rice straw (RS)/corn cob (CC) and peat (P)/compost (C)-based biomixtures. The effect of biomixture preconditioning (10 days incubation prior to pesticide application), pesticide concentration and moisture content was evaluated. Results suggested that conditioning of biomixture greatly affected IMIDA degradation where half-life (t1/2) was reduced by 5–9 times. This was attributed to higher microbial biomass carbon content and dehydrogenase activity in the conditioned biomixtures. Pesticide application in the conditioned biomixture did not show any negative impact on soil microbial parameters. Both pesticides degraded at faster rate in the rice straw-based biomixtures than in the corn cob-based biomixtures. Degradation slowed down with increase in initial concentration of pesticides in biomixture and 1.6–3.0 (AZOXY) and 2.4–3.6 (IMIDA) times increase in t1/2 values was observed. The moisture content of biomixture showed positive effect on degradation which increased when moisture content was increased from 60 to 80% water holding capacity. The effect was significant for IMIDA degradation in the corn cob-based biomixtures and AZOXY degradation in the peat biomixtures. The rice straw-based biomixtures were better in degrading AZOXY and IMIDA and can be used in biopurification systems.

Degradation of Azoxystrobin, Lufenuron and Fenpyroximate Residues in/on Grape Fruits under Field Conditions.

Fungal infection and pests attack arevery serious problems that facing grapes growers in Egypt. Fungicide azoxystrobin, (Azostar® 25%SC), insecticide lufenuron, (Cymax® 5%EC) and acaricide fenpyroximate (Ortus super® 5%EC) are the most common pesticides used to control such pests (downy mildew, grape fruit worm Eudemis botrana and red spider mite, respectively) in Egypt. The present study was carried out to assess persistence Vs. degradation behavior of the mentioned pesticides when sprayed on foliage of grape plants under field conditions during fruiting stage at the recommended and double the recommended rates of application during the season of 2017 in Adam village, El-Nobaria district, El-Behaira Governorate, Egypt. Fruit samples were collected randomly, two hours (initial time) and 1, 3, 7, 14 and 21 days after application. Samples of treated and untreated (control) grape fruits were prepared, extracted, cleaned-up by QuEChERS analytical method before quantification by high performance liquid chromatography with diode array detector (HPLC-DAD) and gas chromatography extended by electron capture detector (GC). The corresponding values for dissipation of the mentioned pesticides initial deposits, degradation percentages of residues, Residual Lifetime 50% (RL50), Residual Lifetime 90% (RL90) and pre-harvest intervals (PHIs) of the tested pesticides were determined. Results revealed that grape fruits remained higher initial amounts by (2.93 and 3.97), (0.82 and 1.14) and (1.74 and 1.94) mg kg-1 azoxystrobin, lufenuron and fenpyroximate for both doses, respectively. As for RL50, RL90 andPHIs, values showed (3.22, 1.73, 1.85 days) and (9.71, 4.22 and 6.31 days) and (5, 6.89, 4.05 days) when the recommended doses were applied and also, (3.80, 10.4 and 6.85 days) and (1.91, 5.02 and 7.12 days) and (2.58, 6.09 and 5.24 days) at the double recommended rates of application, in/on grape, respectively. In general, azoxystrobin, lufenuron and fenpyroximate residue in/on grape fruits had low persistence. In addition, the grape fruits could be consumed safely after 5, 6.89, 4.05 days, respectively from treating by the recommended rate of azoxystrobin, lufenuron and fenpyroximate when compared by the Maximum Residue Limits (MRLs) of the Codex Alimentarius Commission or the European Union (2, 0.01 and 0.01 mg kg-1), respectively.

Determination of the changes in the process of degradation of some pesticides applied in mixtures with plant growth regulators, foliar fertilizers and spreader-stricker in a vineyard

The study conducted in 2015-2016 examined effects of plant growth regulators (PGR), foliar fertilizers (FF) and spreader-sticker (SS) on the process of degradation of pesticides. First physical then chromatographic analyses were conducted in laboratory to determine whether degradation occurred even in spray tanks. In order to determine if changes occurred during the process of decomposition of pesticides in mixtures under field conditions, two experiments were set up in Izmir during the shooting and fruiting of grapevines in 2016. In shooting period, a mixture of azoxystrobin, imidacloprid and metalaxyl was blended with PGR, FF and SS in double and triple combinations to create eight treatments applied to three replicates to determine the process of degradation of active ingredients on leaf samples collected at given intervals. In general, it was observed that degradation of azoxystrobin, imidacloprid and metalaxyl on leaves applied with PGR, FF and SS was slower and the residues did not drop below maximum residue limits even after the preharvest interval. During the fruiting period, a mixture of boscalid, chlorpyrifos ethyl and hexythiazox was applied in the same way as for the shooting period. All mixtures with PGR, FF and SS tended to increase degradation of boscalid, but had no effect on the degradation on chlorpyrifos ethyl and hexythiazox .

Bioaugmentation of Soil Contaminated with Azoxystrobin

The presence of fungicides in the natural environment, either resulting from deliberate actions or not, has become a serious threat to many ecosystems, including soil. This can be prevented by taking appropriate measures to clear the environment of organic contamination, including fungicides. Therefore, a study was conducted aimed at determining the effect of bioaugmentation of soil exposed to azoxystrobin on its degradation and activity of selected enzymes (dehydrogenases, catalase, urease, acidic phosphatase, alkaline phosphatase). A model experiment was conducted for 90 days on two types of soil: loamy sand (pHKCl—5.6) and sandy loam (pHKCl—7.0), which were contaminated by azoxystrobin at 22.50 mg kg−1 DM of soil and inoculated with a specific consortium of microorganisms. Four strains of bacteria were used in the experiment (Bacillus sp. LM655314.1, B. cereus KC848897.1, B. weihenstephanensis KF831381.1, B. megaterium KJ843149.1) and two strains of mould fungi (Aphanoascus terreus AB861677.1, A. fulvescens JN943451.1). Inoculation of soil with the consortium of microorganisms accelerated the degradation of azoxystrobin. The isolated microorganisms were more active in loamy sand because within 90 days azoxystrobin was degraded by 24% (Bacillus sp., B. cereus, B. weihenstephanensis, B. megaterium) to 78% (Aphanoascus terreus, A. fulvescens). In sandy loam, azoxystrobin was degraded by 9% (Aphanoascus terreus, A. fulvescens) to 29% (Bacillus sp., B. cereus, B. weihenstephanensis, B. megaterium and Aphanoascus terreus, A. fulvescens). The activity of soil enzymes was also changed as a result of inoculation of soil with microorganisms. The activity of all of the enzymes under study was found to have increased when soil augmentation was performed.

Enhanced Degradation of Azoxystrobin in Grapes and Model Systems by Ozone Fumigation during Storage

This study was conducted to investigate the natural decline in the residues of the world’s most widely used fungicide, azoxystrobin, in model systems and grapes stored in cold rooms and to determine if ozone fumigation during storage has a contribution to the degradation process. The level of the fungicide gradually decreased both in model systems and grapes with the reduction rates of 53 ± 2 and 29 ± 1%, respectively, at the end of storage. Addition of ozone (1.0 ppm) to the storage atmosphere was found to have a significant influence on fungicide degradation both in model systems and grapes and about 90% reduction rates were recorded. This is the first report demonstrating the accelerated degradation of azoxystrobin by the use of ozone gas treatment.

Degradation profile of azoxystrobin in Andisol soil: laboratory incubation

The fate of azoxystrobin in soil under the effect of different temperature is of interest because application directions specify soil-surface treatments for number of agricultural pests. Temperature is an important factor governing the rate of degradation in soil pore. The purpose of this investigation was to understand better the effect of temperature on the degradation of azoxystrobin in Japanese Andisol soil. This was done through laboratory incubation of soil at three different temperatures (5 °C, 20 °C, 35 °C). First-order kinetics could be used to describe degradation of azoxystrobin under controlled condition of temperature (r2 ˃ 94). The results showed that, during the 120-day incubation period for azoxystrobin, 64%, 70%, and 78% of applied azoxystrobin were degraded at 5 °C, 20 °C, and 35 °C, respectively. By using the Arrhenius equation, the activation energy of degradation of azoxystrobin fungicide was calculated (7.48 ± 1.74 kJ mol−1) in soils, which confirm that temperature had a significant influence on the degradation rate. Q10 value of 1.11, for azoxystrobin, indicated that the response of fungicide dissipation to temperature was large. For azoxystrobin, there was a much larger difference in dissipation rates at 5 °C and 35 °C, indicating that biological and/or chemical degradation of azoxystrobin may have nearly reached its optimum at 35 °C.

Validation of a SPME-GC Method for Azoxystrobin and Pyraclostrobin in Blueberries, and Their Degradation Kinetics

Analytical method for the residues of strobilurins azoxystrobin and pyraclostrobin in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) cou-pled to gas chromatography with micro-electron capture detector. The effect of pH values and fiber coatings were studied. The SPME fiber coating selected was 100 μm PDMS. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged within the 100% - 106% range for azoxystrobin, and 96% - 106% range for pyraclostrobin; and detection and quantification limits were 2.0 and 6.0 μg/kg for azoxystrobin, and 26.0 and 86.0 μg/kg for py-raclostrobin, respectively. Statistical parameters indicated the occurrence of matrix effect; con-sequently calibration was performed on spiked samples. Degradation of azoxystrobin and pyra-clostrobin was studied in blueberry fields located in Concordia, Argentina, with fruits from Emerald and Jewel varieties. The degradation of these fungicides in both blueberry varieties studied followed a first order rate kinetics, and the half-life for azoxystrobin was 11.6 and 17.8 days for Emerald and Jewel cultivars; and for pyraclostrobin was 5.5 and 8.0 days, respectively.

Isolation and characterisation of azoxystrobin degrading bacteria from soil

The first strobilurin fungicides were introduced in 1996, and have since been used in a vast array of disease/plant systems worldwide. The strobilurins now consist of 16 compounds and represent the 2nd most important fungicide group worldwide with 15% of the total fungicide market share. Strobilurins are moderately persistent in soil, and some degradation products (e.g. azoxystrobin acid) have been detected as contaminants of freshwater systems. Little is currently known about the transformation processes involved in the biodegradation of strobilurins or the microbial groups involved. Using sequential soil and liquid culture enrichments, we isolated two bacterial strains which were able to degrade the most widely used strobilurin, azoxystrobin, when supplied as a sole carbon source. 16S rRNA showed that the strains showed homology to Cupriavidus sp. and Rhodanobacter sp. Both isolated strains were also able to degrade the related strobilurin compounds trifloxystrobin, pyraclostrobin, and kresoxim-methyl. An additional nitrogen source was required for degradation to occur, but the addition of a further carbon source reduced compound degradation by approximately 50%. However, 14C radiometric analysis showed that full mineralisation of azosxystrobin to 14CO2 was negligible for both isolates. 16S rRNA T-RFLP analysis using both DNA and RNA extracts showed that degradation of azoxystrobin in soil was associated with shifts in bacterial community structure. However, the phylotypes which proliferated during degradation could not be attributed to the isolated degraders.

Impacts of biochar on bioavailability of the fungicide azoxystrobin: A comparison of the effect on biodegradation rate and toxicity to the fungal community

There is great interest in using biochar (BC) as a soil amendment to provide a long-term repository of carbon to mitigate climate change. BC can have major impacts on soil biogeochemical cycling processes, largely by the sorption and protection of organic matter from microbial turnover. Application of BC to agricultural soil could also affect the efficacy, fate and environmental impact of pesticides. In the current study we investigated the effect of BC on bioavailability of the fungicide azoxystrobin in soil. We found that application of BC had no effect on sorption or degradation of azoxystrobin, even at a rate of 2% w/w. While azoxystrobin reduced dehydrogenase activity, BC addition greatly increased dehydrogenase, although the inhibitory effect of azoxystrobin was still evident in BC amended soil. Using Terminal Restriction Fragment Length Polymorphism of fungal SSU rRNA gene ITS regions it was found that azoxystrobin altered the structure of the soil fungal community, although this effect was dampened by BC addition. BC application had minor effects on fungal community structure. We conclude that measurement of the effect of BC on pesticide bioavailability by analysis of biodegradation rate and non-target effects on fungal community structure gave contrasting conclusions.

Effect of elevated CO2 on degradation of azoxystrobin and soil microbial activity in rice soil

An experiment was conducted in open-top chambers (OTC) to study the effect of elevated CO2 (580 ± 20μmolmol(-1)) on azoxystrobin degradation and soil microbial activities. Results indicated that elevated CO2 did not have any significant effect on the persistence of azoxystrobin in rice-planted soil. The half-life values for the azoxystrobin in rice soils were 20.3days in control (rice grown at ambient CO2 outdoors), 19.3days in rice grown under ambient CO2 atmosphere in OTC, and 17.5days in rice grown under elevated CO2 atmosphere in OTC. Azoxystrobin acid was recovered as the only metabolite of azoxystrobin, but it did not accumulate in the soil/water and was further metabolized. Elevated CO2 enhanced soil microbial biomass (MBC) and alkaline phosphatase activity of soil. Compared with rice grown at ambient CO2 (both outdoors and in OTC), the soil MBC at elevated CO2 increased by twofold. Elevated CO2 did not affect dehydrogenase, fluorescein diacetate, and acid phosphatase activity. Azoxystrobin application to soils, both ambient and elevated CO2, inhibited alkaline phosphates activity, while no effect was observed on other enzymes. Slight increase (1.8-2 °C) in temperature inside OTC did not affect microbial parameters, as similar activities were recorded in rice grown outdoors and in OTC at ambient CO2. Higher MBC in soil at elevated CO2 could be attributed to increased carbon availability in the rhizosphere via plant metabolism and root secretion; however, it did not significantly increase azoxystrobin degradation, suggesting that pesticide degradation was not the result of soil MBC alone. Study suggested that increased CO2 levels following global warming might not adversely affect azoxystrobin degradation. However, global warming is a continuous and cumulative process, therefore, long-term studies are necessary to get more realistic assessment of global warming on fate of pesticide.