Effects Of Azoxystrobin Research Articles

Efficacy of Azoxystrobin 7.5% and Propiconazole 12.5% SE Against Sheath Blight in Rice

Among the fungal diseases causing significant yield loss in rice, sheath blight caused by Rhizoctonia solani Kuhn is the most important ranked the second most important disease worldwide after blast and a serious threat in rice growing areas of the world and causes more economic yield losses. The field experiment was conducted with seven treatments and replicated three times in RBD design at ARS, Gangavati to know the effect of Azoxystrobin 7.5% + Propiconazole 12.5% SE against sheath blight in rice. The variety BPT-5204 was sown in plot size of 5 X 5 m2 with all regular agronomic practices followed as per the standard package of practice of University of Agricultural Sciences, Raichur. It has been found that the fungicide Azoxystrobin 7.5% + Propiconazole 12.5% SE at different doses evaluated was effective in reducing the severity of rice sheath blight and thereby increased the rice grain yield. The treatment Azoxystrobin 7.5% + Propiconazole 12.5% SE @ 625 ml/ha recorded minimum sheath blight of 13.70 and 16.11 per cent PDI with yield of 64.60 q/ha and 63.20 q/ha compared to control treatment 48.70 and 57.96 per cent PDI with grain yield of 54.10 q/ha and 52.40 q/ha during the first and second season, respectively. In the current study, along with reducing sheath blight severity, fungicide treatments minimized grain yield losses in 2 years. Field trial conducted clearly indicated that Azoxystrobin 7.5% + Propiconazole 12.5% SE @ 500 and 625 ml/ha dose can effectively control sheath blight of rice. Azoxystrobin 7.5% + Propiconazole 12.5% w/v SE @ 500 ml/ha was at par with higher dose and resulted better yield than other treatments.

Effect of azoxystrobin on the physiology, morphology, and sclerotial formation of Rhizoctonia solani from tobacco

Effect of azoxystrobin on the physiology, morphology, and sclerotial formation of Rhizoctonia solani from tobacco

Effect of azoxystrobin on tobacco leaf microbial composition and diversity.

Azoxystrobin, a quinone outside inhibitor fungicide, reduced tobacco target spot caused by Rhizoctonia solani by 62%, but also affected the composition and diversity of other microbes on the surface and interior of treated tobacco leaves. High-throughput sequencing showed that the dominant bacteria prior to azoxystrobin treatment were Methylobacterium on healthy leaves and Pseudomonas on diseased leaves, and the dominant fungi were Thanatephorous (teleomorph of Rhizoctonia) and Symmetrospora on healthy leaves and Thanatephorous on diseased leaves. Both bacterial and fungal diversity significantly increased 1 to 18 days post treatment (dpt) with azoxystrobin for healthy and diseased leaves. For bacteria on healthy leaves, the relative abundance of Pseudomonas, Sphingomonas, Unidentified-Rhizobiaceae and Massilia declined, while Methylobacterium and Aureimonas increased. On diseased leaves, the relative abundance of Sphingomonas and Unidentified-Rhizobiaceae declined, while Methylobacterium, Pseudomonas and Pantoea increased. For fungi on healthy leaves, the relative abundance of Thanatephorous declined, while Symmetrospora, Sampaiozyma, Plectosphaerella, Cladosporium and Cercospora increased. On diseased leaves, the relative abundance of Thanatephorous declined, while Symmetrospora, Sampaiozyma, Plectosphaerella, Cladosporium, Phoma, Pantospora and Fusarium, increased. Compared to healthy leaves, azoxystrobin treatment of diseased leaves resulted in greater reductions in Thanatephorous, Sphingomonas and Unidentified-Rhizobiaceae, a greater increase in Methylobacterium, and similar changes in Phoma, Fusarium, Plectosphaerella and Cladosporium. Azoxystrobin had a semi-selective effect altering the microbial diversity of the tobacco leaf microbiome, which could be due to factors, such as differences among bacterial and fungal species in sensitivity to quinone outside inhibitors, ability to use nutrients and niches as certain microbes are affected, and metabolic responses to azoxystrobin.

Growth-inhibiting effect of azoxystrobin and its ability to inhibit sugar consumption in winter wheat sprouts and roots

This study aimed to assess the prospects for the use of azoxystrobin, a fungicide of the strobilurin class, for increasing the resistance of winter wheat to low temperatures. The effect of azoxystrobin on growth processes, cell viability and the content of water-soluble carbohydrates in winter wheat (Triticum aestivum L.), the Ikutskaya variety, was studied. In comparison with other synthetic strobilurins, azoxystrobin is more frequently used in multicomponent fungicidal preparations. Azoxystrobin is a broad-spectrum fungicide that inhibits complex III of the mitochondrial electron transport chain. Experiments were carried out in laboratory conditions using 3-day-old etiolated winter wheat sprouts. The sprouts were grown in a dark place at a temperature of +24 °C on azoxystrobin solutions dissolved in a 0.36% aqueous solution of dimethyl sulfoxide, distilled water and a 0.36% dimethyl sulfoxide solution. The effect of various azoxystrobin concentrations (2.5, 5, 10 and 20 μM) on the growth of sprouts and roots was assessed, along with the viability of sprout and root cells. Azoxystrobin had a concentration-dependent growth-inhibiting effect on sprouts and roots. At concentrations of 2.5 μM and 20 μM, the inhibition degree for sprouts varied from 2.8% to 41.7%, respectively. For roots, these values comprised 34.6 and 63.1%, respectively. The growth-inhibiting effect was not accompanied by a decrease in the cell viability of sprouts and roots, which was assessed using in vivo staining with fluorescein diacetate (FDA). The effect of azoxystrobin at a concentration of 10 μM on the sugar content in germinated sprouts was also evaluated. At this concentration of azoxystrobin, the sugar content was higher by 3.6% in sprouts germinated on a dimethyl sulfoxide solution. Since growth inhibition and sugar accumulation are important factors in plant adaptation to low temperatures, further research into effects of azoxystrobin on the physiological and biochemical parameters of plants associated with the development of low-temperature resistance seems justified.

Evaluation of the acute toxic effect of azoxystrobin on non-target crayfish (Astacus leptodactylus Eschscholtz, 1823) by using oxidative stress enzymes, ATPases and cholinesterase as biomarkers

Azoxystrobin is a broad-spectrum fungicide used worldwide. Since azoxystrobin spreads to large areas, its toxic effects on non-target organisms have aroused interest. In this study, the acute toxicity (96 h) of azoxystrobin on the crayfish (Astacus leptodactylus) was examined by using various biomarkers. The 96 h-LC50 dose (1656 mg L−) and its three sub-doses (828, 414, 207 mg L−1) were applied to crayfish. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were increased significantly compared to the control in hepatopancreas, gill and muscle tissues. The activities of acetylcholinesterase (AChE) and glutathione S-transferase (GST) increased, and glutathione reductase (GR) activity decreased significantly in hepatopancreas. Level of reduced glutathione (GSH) decreased significantly. The content of malondialdehyde (MDA) increased in a dose-dependent manner in all azoxystrobin treatments with the exception of the lowest dose (207 mg L-1)treatment. ATPases (Na+/K+ -ATPase, Mg2+ -ATPase, Ca2+ -ATPase, total ATPase) were significantly inhibited in gill and muscle tissues. The results of the present study indicate that azoxystrobin induces oxidative stress, and has adverse effects on activities of AChE and ATPases in crayfish.

АНАЛИЗ ЭФФЕКТИВНОСТИ И ФИТОТОКСИЧНОСТИ НОВОГО ТРЕХКОМПОНЕНТНОГО ФУНГИЦИДА

Due to the inherent pathogenic fungi that affect crops, resistance to chemical remedies, there is a need to update the compositions of preparations. The purpose of this study was the development of a new chemical preparation for the protection of grain crops. To achieve this goal, a comparison was made between the effects of azoxystrobin, prothioconazole and prochloraz on wheat seeds and seedlings in the initial stages of growth. The studies were carried out in 2017-2018 at the Institute of Biology of the University of Warsaw. The effectiveness of fungicidal mixtures, their inhibitory effect on the growth was analyzed. And the most optimal doses were found for the further development of a new plant protection preparation.

Membrane hyperpolarization and depolarization of rat thymocytes by azoxystrobin, a post harvest fungicide

Azoxystrobin, a broad-spectrum fungicide, has been increasingly used in the agricultural industry. In Japan in 2018, azoxystrobin at five times the normal limit was detected in a shipment of Australian barley that had been used in food products. Therefore, the effects of azoxystrobin need to be carefully examined to predict potential adverse reactions in humans. In this study, the effects of azoxystrobin on the membrane potential and intracellular Ca2+ levels of thymocytes have been photochemically examined using flow cytometry. Azoxystrobin hyperpolarized plasma membrane potential. This hyperpolarization appeared to be due to the activation of Ca2+-dependent K+ channels, as both the removal of extracellular Ca2+ and addition of charybdotoxin attenuated the observed hyperpolarization. In the presence of quinine, an anti-malarial drug that blocks Ca2+-dependent K+ channels, azoxystrobin depolarized the membranes instead. Azoxystrobin increased intracellular Ca2+ levels in a concentration-dependent manner through the influx of extracellular Ca2+ and intracellular release of Ca2+, as confirmed by reduction in azoxystrobin-induced response in the absence of extracellular Ca2+. It appears likely that azoxystrobin at micromolar concentrations modifies membrane ion permeability in thymocytes. Since changes in membrane potential and intracellular Ca2+ levels occur during typical physiological lymphocyte responses, azoxystrobin may disturb lymphocyte function.

Effects of two strobilurins (azoxystrobin and picoxystrobin) on embryonic development and enzyme activities in juveniles and adult fish livers of zebrafish (Danio rerio)

Azoxystrobin and picoxystrobin are two primary strobilurin fungicides used worldwide. This study was conducted to test their effects on embryonic development and the activity of several enzyme in the zebrafish (Danio rerio). After fish eggs were separately exposed to azoxystrobin and picoxystrobin from 24 to 144 h post fertilization (hpf), the mortality, hatching, and teratogenetic rates were measured. Additionally, effects of azoxystrobin and picoxystrobin on activities of three important antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD)] and two primary detoxification enzymes [carboxylesterase (CarE) and glutathione S-transferase (GST)] and malondialdehyde (MDA) content in zebrafish larvae (96 h) and livers of adult zebrafish of both sexes were also assessed for potential toxicity mechanisms. Based on the embryonic development test results, the mortality, hatching, and teratogenetic rates of eggs treated with azoxystrobin and picoxystrobin all showed significant dose- and time-dependent effects, and the 144-h LC50 values of azoxystrobin and picoxystrobin were 1174.9 and 213.8 μg L−1, respectively. In the larval zebrafish (96 h) test, activities of CAT, POD, CarE, and GST and MDA content in azoxystrobin and picoxystrobin-treated zebrafish larvae increased significantly with concentrations of the pesticides compared with those in the control. We further revealed that azoxystrobin and picoxystrobin exposure both caused significant oxidative stress in adult fish livers and the changes differed between the sexes. Our results indicated that picoxystrobin led to higher embryonic development toxicity and oxidative stress than azoxystrobin in zebrafish and the male zebrafish liver had stronger ability to detoxify than that of the females.

Impact of three different fungicides on fungal epi- and endophytic communities of common bean (Phaseolus vulgaris) and broad bean (Vicia faba)

ABSTRACTIn this study, the impacts of three different fungicides to fungal phyllosphere communities on broad bean (Vicia faba, Fabaceae) and common bean (Phaseolus vulgaris, Fabaceae) were analyzed. The fungicides included copper, sulfur, and azoxystrobin. The plants were sowed, grown, and treated under conditions occurring in conventional and organic farming. A culture-based approach was used to identify changes in the phyllosphere fungal community after the treatment. Different effects on species richness and growth index of the epiphytic and endophytic communities for common bean and broad bean could be shown. Treatments with sulfur showed the weakest effect, followed by those based on copper and the systemic azoxystrobin, which showed the strongest effect especially on endophytic communities. The epiphytic fungal community took five weeks to recover after treatment with azoxystrobin. However, the effect of azoxystrobin on the endophytic community lasted more than five weeks. Finally, the data suggest that the surface structure of the host leaves have a huge impact on the mode of action that the fungicides exert.

A Strobilurin Fungicide Relieves Bipolaris oryzae‐Induced Oxidative Stress in Rice

AbstractAlthough strobilurins are one of the most effective and broad spectrum classes of systemic fungicides, they may also increase plant stress tolerance by modulating the activity of antioxidant enzymes. To address this issue, the effect of azoxystrobin (Az) on the activity of antioxidant enzymes and on the concentrations of antioxidant metabolites and oxidative stress‐related compounds was studied in rice plants (cv. Metica‐1) either inoculated or not with Bipolaris oryzae, the causal agent of brown spot (BS). The Az minimally affected the enzyme activities, but consistently increased the glutathione reduced (GSH) concentrations in the noninoculated plants. The activities of superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione peroxidase, glutathione reductase and glutathione‐S‐transferase were increased upon B. oryzae infection, but such increases were greatly limited in the Az‐sprayed plants. Catalase activity decreased in the inoculated plants compared to the noninoculated plants regardless of fungicide treatment. The GSH concentration increased in response to the B. oryzae infection, and the Az‐sprayed plants sustained higher levels of GSH at advanced stages of fungal infection than did the nonsprayed plants. The inoculated plants exhibited an extensive oxidative stress as evidenced by higher concentrations of hydrogen peroxide and malondialdehyde compared to the noninoculated plants, but lower and later increases were recorded in the Az‐sprayed plants than in the nonsprayed plants. Therefore, Az greatly reduces B. oryzae‐induced oxidative stress by limiting BS development rather than by activating antioxidant enzymes. The GSH, however, seems to be Az‐modulated, and this may partially explain the constrained oxidative stress observed in the Az‐sprayed plants.

Enzymatic activities and microbial biomass in black soil as affected by azoxystrobin

As a high-efficiency and broad-spectrum new fungicide, azoxystrobin has been widely applied on various crops. However, little is known about the effect of azoxystrobin on microbial biomass and enzymatic activities in black soils. A laboratory experiment was conducted to study the impact of azoxystrobin application at different concentration levels (0, 0.1, 1.0 and 10.0 mg kg−1) on cultivable microbial biomass and soil respiration in black soil. Urease, protease, dehydrogenase and catalase activities were also monitored on days 7, 14, 21 and 28. The results showed that the populations of cultivable bacteria, fungi and actinomycetes were seriously inhibited when the incubation time was over 7 days. The variation in soil respiration showed similar inhibition tendencies on the 14th, 21st and 28th days. A significant increase in the activity of catalase in black soils in response to higher levels (1 and 10 mg kg−1) of azoxystrobin was observed only on the 28th day. Azoxystrobin had similar significantly negative influences on the activities of urease, protease and dehydrogenase; however, the level of inhibition depended on the doses of azoxystrobin and the time after its application.

Effect of azoxystrobin and kresoxim‐methyl on rice blast and rice grain yield in China

AbstractSensitivity to azoxystrobin and kresoxim‐methyl of 80 single‐spore isolates of Magnaporthe oryzae was determined. The EC50 values for azoxystrobin and kresoxim‐methyl in inhibiting mycelial growth of the 80 M. oryzae isolates were 0.006–0.056 and 0.024–0.287 µg mL−1, respectively. The EC50 values for azoxystrobin and kresoxim‐methyl in inhibiting conidial germination of the M. oryzae populations were 0.004–0.051 and 0.012–0.105 µg mL−1, respectively. There was significant difference in sensitivity to azoxystrobin or kresoxim‐methyl between the tested isolates representing differential sensitivity to carbendazim (MBC) and kitazin P (IBP); however, there was no correlation between this difference in sensitivity to azoxystrobin or kresoxim‐methyl and sensitivity to MBC or IBP, indicating that there was no cross‐resistance between azoxystrobin or kresoxim‐methyl and MBC or IBP. In the protective and curative experiments, kresoxim‐methyl exhibited higher protective and curative activity than azoxystrobin when applied at 150 and 250 µg mL−1 accordingly, while azoxystrobin exhibited stronger inhibitory activity against M. oryzae isolates than that of kresoxim‐methyl in the in vitro test. The results of field experiments also suggested that both azoxystrobin and kresoxim‐methyl at 187.5 g.a.i. ha−1 gave over 73% control efficacy in both sites, exhibiting excellent activity against rice blast. Taken together, azoxystrobin and kresoxim‐methyl could be a good substitute for MBC or IBP for controlling rice blast in China, but should be carefully used as they were both at‐risk.

Study of interaction of low doses of ionizing radiation with selected pesticides on Artemia franciscana

The aim of our study was to observe the effect of low doses of ionizing radiation, azoxystrobin and glyphosate separately as well as in their mutual combinations on the lethality of Artemia franciscana. Increasing intensity of agricultural production leads to continual exposure of animals to pesticide residues. Animals could be exposed to these negative factors in case of possible nuclear accident. A total of 1000 nauplia, randomly placed in 20 groups (1 control and 19 experimental groups), were irradiated with gamma rays (0, 20, 30, 40 or 50 Gy) and were kept in solution of standardized sea water and standardized sea water with addition of pesticides (azoxystrobin at a concentration of 0.0001 g·l-1 and glyphosate at a concentration of 0.5 g·l-1 individually or in combination). A significant increase of lethality was observed after 48, 72 and 96 h of exposure to only azoxystrobin, but also in the group exposed to the combined effect of azoxystrobin and glyphosate at all time intervals. On the other hand, a significant decrease of lethality was observed in those groups exposed to ionizing radiation even at the dose of 30 Gy at all time intervals compared to non-irradiated groups. These results confirm the toxicity of azoxystrobin to aquatic organisms; non-toxicity of glyphosate to crustaceans and support the theory of radiation hormesis at the level of 30 Gy radiation dose.

Effect of Azoxystrobin Based Fungicides in Management of Chilli and Tomato Diseases

Chilli and tomato are two major vegetable crops of the world with India being one of the important producers. Vulnerable to many diseases, chemical control has been the most effective method adopted by farmers to protect their crops from fungal pathogens. The pathogens have started developing resistance against the conventionally used fungicides recommended to the farmers. Second generation fungicides have proved as a new ray of hope in better management of diseases under field conditions. Strobilurins have not been much tested in Indian subcontinent for their efficacy against many diseases. Two azoxystrobin based fungicides ONESTAR 23 % SC and AMISTAR 23 % SC were used to study their efficacy along with other commonly used fungicides, against blight disease of tomato and fruit rot and powdery mildew of chilli in Varanasi for 2 years from 2010–2011 to 2011–2012. Maximum disease reduction was observed in plants treated with Onestar 23 % SC and Amistar 23 % SC in both chilli and tomato (70–78 % reduction recorded in case of chilli while 69–71 % recorded in case of tomato) with enhanced yield (1.29 fold increment in chilli and 1.39 fold increment in tomato) in both seasons. No phytotoxicity symptoms were observed in the plants against the fungicides tested suggesting the importance of using fungicides in proper dose and at proper interval.

Effects of azoxystrobin, chlorothalonil, and ethoprophos on the reproduction of three terrestrial invertebrates using a natural Mediterranean soil

The potential terrestrial toxicity of three pesticides, azoxystrobin, chlorothalonil, and ethoprophos was evaluated using reproduction ecotoxicological tests with different non-target species: the collembolan Folsomia candida, the earthworm Eisenia andrei, and the enchytraeid Enchytraeus crypticus. All reproduction tests were performed with natural soil from a Mediterranean agricultural area (with no pesticide residues) in order to improve the relevance of laboratory data to field conditions. Controls were performed with natural and standard artificial soil (OECD 10% OM). The fungicide azoxystrobin showed the highest toxicity to earthworms (EC50=42.0mga.i.kg−1 dw soil). Collembolans were the most sensitive taxa in terms of sublethal effects of chlorothalonil with an EC50 of 31.1mga.i.kg−1 dw soil followed by the earthworms with an EC50 of 40.9mga.i.kg−1 dw soil. The insecticide ethoprophos was the most toxic to collembolans affecting their reproduction with an EC50 of 0.027mga.i.kg−1 dw soil. Enchytraeids were generally the least sensitive of the three species tested for long-term effects. Earthworms were not always the most sensitive species, emphasizing the need to increase the number of mandatory assays with key non-target organisms in the environmental risk assessment of pesticides.

Effect of planting dates and azoxystrobin fungicide application regimes on common rust of maize

A study over two growing seasons evaluated the efficacy and cost effectiveness of azoxystrobin (Amistar® SC), applied at different action thresholds and plant growth stages, on the incidence and severity of common rust of maize grown in the Pukekohe, New Zealand. Azoxystrobin applied as a preventative before disease symptoms appeared, or at the onset of disease symptoms, gave equal or better control than fungicide applications applied at 3% and 6% rust thresholds. However, using a 3% disease threshold up to the tasselling stage to time the application of azoxystrobin, controlled common rust in the more severe rust season (2008–09) and saved fungicide application costs associated with preventative (calendar) or disease-onset applications of azoxystrobin in the less severe rust season (2007–08) when the rust levels did not reach 3% by the tasselling stage. The maize hybrid 34D71 used was classified as moderately susceptible to common rust and, from the research presented here, it appears that although azoxystrobin applications reduced common rust severity, the lack of yield gains suggests that azoxystrobin applications in northern New Zealand may be economic only when growing highly susceptible maize varieties.

Effect of Azoxystrobin 8.3%w/w + Mancozeb 68.75% on Powdery and Downy mildew Pathogens under In vitro condition

Field surveys were conducted in 3 major grapevine growing districts in Tamil Nadu viz., Coimbatore, Theni and Dindugal. The downy mildew infection on leaves was the highest (PDI 76.92 in Cumbum of Theni district. In the survey on the incidence of powdery mildew showed that the highest incidence of PDI on leaves, inflorescence and fruits in Cumbum of Theni with records of 65.49, 63.56, 61.23 percent. The pathogenecity test revealed that the downy mildew isolate D-TC1 of Theni district was found to be more virulent with highest PDI of (42.35). The powdery mildew isolate of Cumbum (P-TC1) of Theni district was found to be more virulent by recording the maximum PDI of (36.94). Among the different fungicide tested against spore germination of P.viticola, Azoxystrobin 8.3%w/w + Mancozeb 68.75 at 0.36 per cent recorded 89.26 % inhibition . The fungicide Azoxystrobin 8.3% + Mancozeb 68.75 in all three concentrations, was found to be superior in inhibiting the spore germination of U. necator by recording 90.27%, 89.91%, 80.70% respectively in 0.36, 0.30 and 0.24 % concentrations.

Effect of fungicide application on Wheat Head Blight, occurrence of Fusarium spp. and mycotoxin production

Effect of fungicide application on Wheat Head Blight, occurrence of Fusarium spp. and mycotoxin production The aim of the study was to determine if azoxystrobin and metconazole used for the control of wheat FHB at half, full, and quarter more the recommended dose rate may affect in differentiated way on the occurrence of Fusarium spp. and their ability to mycotoxin production in harvested grain, in wheat ears artificially inoculated with two DON-producing isolates of F. culmorum. Macroscopic evaluation showed high incidence of fusariosis. Plant health in the plots where the heads were artificially inoculated and fungicide was not applied was similar to the protected ones. Only increasing the dose metconazole resulted in a stronger reduction of fusariosis. The advantageous effect of azoxystrobin was not observed. Mycological analysis of harvested grain showed the presence of a number of F. culmorum, but from samples sprayed with metconazole it was isolated in smaller quantities. Also F. avenaceum, F. graminearum, F. poae and F. tricinctum were isolated. Molecular analysis showed the presence of F. culmorum in all samples of harvested grain. Also genes from Tri cluster were identified, involved in the synthesis of type-A and type-B trichothecenes - especially DON and 3Ac-DON. Chromatography revealed the presence of small quantities of mycotoxins. In all samples DON and 3Ac-DON were predominant. In general, F. culmorum isolate, which caused weaker symptoms of FHB and was less numerously isolated from grain that the other one, produced smaller amounts of mycotoxins. Samples protected with azoxystrobin contain the largest quantities of DON. Effect of different doses of fungicides on the number of mycotoxins was not clearly established.

Effect of azoxystrobin on activities of antioxidant enzymes and alternative oxidase in wheat head blight pathogens Fusarium graminearum and Microdochium nivale

Wheat head blight pathogens Fusarium graminearum and Microdochium nivale have distinct sensitivities to strobilurin fungicides, which inhibit activity of complex III in the mitochondrial electron transport chain. When mycelia were cultured in medium with the strobilurin fungicide azoxystrobin (AZ), F. graminearum increased its oxygen-consumption, but M. nivale, which is more sensitive than Fusarium species to strobilurins, did not. There was no increase in oxygen consumption in F. graminearum by the treatment with AZ and alternative oxidase (AOX) inhibitor n-propyl gallate. AZ enhanced the generation of intracellular H2O2 in both fungi. Activities of antioxidant enzymes in M. nivale were consistently higher than in F. graminearum. Quantification of AOX transcripts by real-time PCR indicated that transcription of AOX in F. graminearum and M. nivale was induced by AZ, suggesting that AOX activities in both fungi are regulated at the transcriptional level. AOX transcription in F. graminearum was rapidly induced by AZ and reached a maximum by 60 min after treatment. On the contrary, induction in M. nivale was low and slow. These results suggest that differential ability of F. graminearum and M. nivale to activate AOX transcription is involved in the difference in their sensitivity to AZ.

Effect of Azoxystrobin on Oxygen Consumption and cyt b Gene Expression of Colletotrichum capsici from Chilli Fruits

Azoxystrobin acts as an inhibitor of electron transport by binding to the Qo center of cytochrome b ( cyt b). Resistance to azoxystrobin was usually caused by the point mutation of cyt b gene or by the induction of alternative respiration. Oxygen consumption test for mycelia of Colletotrichum capsici showed that azoxystrobin inhibited mycelial respiration within 12 h; however, as time went on, the respiration of the mycelia recovered when the mycelia were treated with azoxystrobin and salicylhydroxamic acid (SHAM, a known inhibitor of alternative respiration), and the oxygen consumption of the mycelia could not be inhibited. Meanwhile, cytochrome b ( cyt b) gene expression increased with the recovery of mycelial respiration. The increased cyt b gene expression might play a role in the development of resistance to azoxystrobin in C. capsici.