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1.
Pestic Biochem Physiol ; 158: 18-24, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31378355

RESUMO

Outbreaks of bitter rot were observed in three commercial apple orchards in Illinois despite best management efforts during the 2018 production season. Three isolates from symptomatic fruit from these orchards and two isolates from an orchard in South Carolina were identified to the species level using morphological tools and calmodulin, glyceraldehyde-3-phosphate dehydrogenase, and beta-tubulin gene sequences. The isolates from Illinois were identified as Colletotrichum siamense of the Colletotrichum gloeosporioides species complex and the ones from South Carolina as Colletotrichum fioriniae and Colletotrichum fructicola of the Colletotrichum acutatum and the C. gloeosporioides species complex, respectively. Two of the three C. siamense isolates from Illinois were resistant to azoxystrobin and thiophanate-methyl as determined in mycelial growth tests in vitro. EC50 values were >100 µg/ml for both fungicides. One isolate was only resistant to azoxystrobin. None of the isolates from South Carolina was resistant to either of the two compounds. All five isolates were sensitive to fludioxonil (EC50 values <0.1 µg/ml), propiconazole (EC50 values ranged from 0.15 to 0.36 µg/ml), and benzovindiflupyr (EC50 values ranged from <0.1 to 0.33 µg/ml). Resistance in C. siamense to azoxystrobin and thiophanate-methyl was confirmed in detached fruit studies using apples treated with label rates of registered product. Resistance to thiophanate-methyl in C. siamense was based on E198A mutation in b-tubulin gene, whereas resistance to azoxystrobin was based on G143A in cytochrome b (CYTB). One isolate resistant to azoxystrobin possessed no amino acid variation in CYTB. This study shows that quinone outside inhibitor fungicide resistance in Colletotrichum from apple has emerged and is being selected for in Illinois apple orchards by current spray strategies. Resistance monitoring may alert growers to potential threats, but the employment of molecular tools based on current knowledge of resistance mechanisms will provide incomplete results.


Assuntos
Colletotrichum/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Malus/microbiologia , Benzimidazóis/farmacologia , Colletotrichum/genética , Citocromos b/genética , Citocromos b/metabolismo , Dioxóis/farmacologia , Farmacorresistência Fúngica/genética , Frutas/microbiologia , Malus/genética , Norbornanos/farmacologia , Pirazóis/farmacologia , Pirimidinas/farmacologia , Pirróis/farmacologia , Estrobilurinas/farmacologia , Tiofanato/farmacologia , Triazóis/farmacologia
2.
J Agric Food Chem ; 67(33): 9220-9231, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31347838

RESUMO

Slow-release fungicide formulations (azoxystrobin, epoxiconazole, and tebuconazole) shaped as pellets and granules in a matrix of biodegradable poly(3-hydroxybutyrate) and natural fillers (clay, wood flour, and peat) were constructed. Infrared spectroscopy showed no formation of chemical bonds between components in the experimental formulations. The formulations of pesticides had antifungal activity against Fusarium verticillioides in vitro. A study of biodegradation of the experimental fungicide formulations in the soil showed that the degradation process was mainly influenced by the type of formulation without significant influence of the type of filler. More active destruction of the granules led to a more rapid accumulation of fungicides in the soil. The content of fungicides present in the soil as a result of degradation of the formulations and fungicide release was determined by their solubility. Thus, all formulations are able to function in the soil for a long time, ensuring gradual and sustained delivery of fungicides.


Assuntos
Argila/química , Preparações de Ação Retardada/química , Composição de Medicamentos/métodos , Fungicidas Industriais/química , Hidroxibutiratos/química , Poliésteres/química , Solo/química , Madeira/química , Preparações de Ação Retardada/farmacologia , Portadores de Fármacos/química , Composição de Medicamentos/instrumentação , Compostos de Epóxi/química , Compostos de Epóxi/farmacologia , Fungicidas Industriais/farmacologia , Fusarium/efeitos dos fármacos , Cinética , Pirimidinas/química , Pirimidinas/farmacologia , Estrobilurinas/química , Estrobilurinas/farmacologia , Triazóis/química , Triazóis/farmacologia
3.
J Agric Food Chem ; 67(33): 9232-9240, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31347839

RESUMO

The hydrophobic wax layer of pepper fruit (Capsicum frutescens L.) increases the importance of selecting adjuvants that improve the wetting property of droplets on the target organism and increase the effective utilization of fungicides. In this study, the effect of adjuvants including nonionic, cationic, organosilicone, and oils on the wettability of fungicides was determined. The critical micelle concentrations for S903 (organosilicone), 1227 (cationic), AEO-5 (nonionic), GY-Tmax (oil), and XP-2 (oil) were 25, 1000, 100, 200, and 500 mg/L, respectively. Interface behaviors and in vivo tests suggested that adjuvants at appropriate concentrations (S903, 2.5 mg/L; 1227, 100 mg/L; AEO-5, 1 mg/L; GY-Tmax, 50 mg/L; and XP-2, 5 mg/L) resulted in optimum efficiency. Adjuvants significantly increased the inhibitory activity of pyraclostrobin against the mycelial growth, spore germination, and germ tube elongation of Colletotrichum scovillei by 41.3-58.8%, 28.2-44.6%, and 27.8-39.8%, respectively. Pyraclostrobin amended with S903 and XP-2 showed higher efficacy against anthracnose than the fungicide alone on pepper fruit. The increased efficacy may have resulted from the changed crystal morphology (ellipses of similar sizes), improved wettability, and rainfastness. A structural equation model indicated that surface tension and retention play the most important roles in the application properties of fungicide. In field experiments, the efficacy of pyraclostrobin with adjuvants showed no significant difference with pyraclostrobin alone, which indicated that, except for adjuvants, other spraying technologies are important for improving the field performance of fungicides. These results provide a foundation for the synthesis of highly efficient fungicides based on crystal structure and for the sustainable management of pepper anthracnose.


Assuntos
Portadores de Fármacos/química , Fungicidas Industriais/química , Estrobilurinas/química , Capsicum/microbiologia , Colletotrichum/efeitos dos fármacos , Colletotrichum/crescimento & desenvolvimento , Cristalização , Frutas/microbiologia , Fungicidas Industriais/farmacologia , Micelas , Compostos de Organossilício/química , Doenças das Plantas/microbiologia , Estrobilurinas/farmacologia , Molhabilidade
4.
Plant Dis ; 103(7): 1657-1664, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31082320

RESUMO

Adding adjuvants improved the affinity of fungicide droplets to cucumber leaves infected with powdery mildew (Podosphaera xanthii) and subsequent efficacy of fungicide treatments in reducing the disease. The affinity of oil adjuvants was quantified by adhesional tension and "work of adhesion". Oil adjuvant-fungicide mixtures were applied to plants in field experiments to evaluate their effectiveness in disease prevention. Both the adhesional tension and work of adhesion of the adjuvants at selected concentrations increased on powdery-mildew-infected cucumber leaves more than on healthy cucumber leaves. The adjuvant GY-Tmax (GYT) displayed the best surface activity or "surfactivity" in enhancing the affinity and adherence of droplets to powdery-mildew-infected cucumber leaves, while epoxidized soybean oil (ESO), methyl oleate, and biodiesel exhibited much lower effects in terms of the surface tension, contact angle, adhesional tension, and work of adhesion. Field experiments determined that the combination of GYT at 1,000 mg liter-1 and pyraclostrobin (150 g a.i. ha-1) was most effective (91.52%) in controlling cucumber powdery mildew. Pyraclostrobin with ESO was also highly effective (ranging from 77.54 to 89.65%). The addition of oil adjuvants, especially GYT and ESO, to fungicide applications can be an effective strategy to enhance the efficacy of pesticides in controlling plant diseases by modifying the affinity of fungicide droplets to symptomatic leaves.


Assuntos
Ascomicetos , Cucumis sativus , Óleos , Estrobilurinas , Ascomicetos/efeitos dos fármacos , Ascomicetos/fisiologia , Fungicidas Industriais/farmacologia , Óleos/farmacologia , Folhas de Planta/microbiologia , Estrobilurinas/farmacologia
5.
Plant Dis ; 103(8): 1910-1917, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31140926

RESUMO

The occurrence of fungal brown spot, caused by Bipolaris oryzae, has increased in cultivated wild rice (Zizania palustris) paddies in spite of the use of azoxystrobin-based fungicides. The active ingredient blocks electron transfer at the quinone outside inhibitor (QoI) site in the mitochondrial cytochrome b within the bc1 complex, thus obstructing respiration. The in vitro averaged EC50 of baseline isolates collected in 2007 before widespread fungicide use was estimated to be 0.394 µg/ml with PROBIT and 0.427 µg/ml with linear regression analyses. Isolates collected during 2008, 2015, and 2016 had a range of sensitivity as measured by relative spore germination (RG) at a discriminatory dose of 0.4 µg/ml azoxystrobin. Isolates with a higher (≥80%) and lower RG (≤40%) had the wild type nucleotides at amino acid positions F129, G137, and G143 of cytochrome b, sites known to be associated with QoI fungicide resistance. Two Group I introns were found in the QoI target area. The splicing site for the second intron was found immediately after the codon for G143. A mutation for fungicide resistance at this location would hinder splicing and severely reduce fitness. B. oryzae expresses an alternative oxidase in vitro, which allows the fungus to survive inhibition of respiration by azoxystrobin. This research indicates that B. oryzae has not developed resistance to QoI fungicides, although monitoring for changes in sensitivity should be continued. Judicious use of QoI fungicides within an integrated disease management system will promote an effective and environmentally sound control of the pathogen in wild rice paddies.


Assuntos
Ascomicetos , Farmacorresistência Fúngica , Oryza , Pirimidinas , Estrobilurinas , Ascomicetos/efeitos dos fármacos , Oryza/microbiologia , Pirimidinas/farmacologia , Estrobilurinas/farmacologia
6.
Plant Dis ; 103(7): 1458-1463, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31025906

RESUMO

Botryosphaeria dothidea is an important fungal pathogen that causes apple ring rot, which can significantly reduce apple yield. Fungicide applications are the main control measure of apple ring rot worldwide. Pyraclostrobin is a quinone outside inhibitor (QoI) fungicide that has yet to be registered for control of B. dothidea in China. Baseline sensitivity of B. dothidea to pyraclostrobin (EC50 of mycelial growth inhibition) was assessed for 97 isolates collected in Shandong Province. The EC50 values ranged from 0.7010 to 7.1378 µg/ml with the mean value of 3.0870 µg/ml and displayed a unimodal frequency distribution. After cultured on fungicide-free PDA medium or on apples for multiple generations, the B. dothidea-resistant isolates (RST) remained resistant to pyraclostrobin, but exhibited similar virulence as the susceptible isolates (ST). Cross-resistance investigation revealed that pyraclostrobin was not cross-resistant to tebuconazole, flusilazole, carbendazim, and iprodione. Field evolution showed that pyraclostrobin at 200 and 250 g a.i./ha provided greater than 80% control efficacy against apple ring rot disease when applied as a therapeutic or preventive fungicide. The efficacy was similar to fungicides that have been registered for apple.


Assuntos
Ascomicetos , Malus , Estrobilurinas , Ascomicetos/efeitos dos fármacos , China , Fungicidas Industriais/farmacologia , Concentração Inibidora 50 , Malus/microbiologia , Estrobilurinas/farmacologia
7.
Plant Dis ; 103(6): 1319-1325, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30998417

RESUMO

Anthracnose is one of the most common diseases in strawberry plants. Colletotrichum gloeosporioides is the major cause of anthracnose in China, including Zhejiang Province. Early, specific, reliable, and time-saving detection is urgently needed to prevent the further spread of C. gloeosporioides, guiding farmers to utilize chemicals to control anthracnose. In this study, we showed that the high resistance to pyraclostrobin, caused by a point mutation at codon 143 (GGT→GCT) in the cytochrome b gene of C. gloeosporioides was prevalent in the strawberry growing regions, and we developed a loop-mediated isothermal amplification (LAMP) assay as a detection method. Primer sets S0 and S4 could be used to specifically detect C. gloeosporioides isolates and the G143A mutations, respectively. A detection limit of 10-2 ng (10 pg), which is at least 10-fold more sensitive than conventional polymerase chain reaction, was achieved by the LAMP assay. Here, we utilized lateral-flow devices (LFDs), nitrocellulose membranes that can absorb nucleic acids, to acquire the total genomic DNA of strawberry plants within 2 min. The LFD membranes were used as DNA templates for the LAMP assays to accurately detect strawberry plants infected with C. gloeosporioides. This diagnostic method for strawberry anthracnose was accomplished within 1 h, including the sample preparation and LAMP assays. Collectively, we developed a sensitive and practical method for monitoring C. gloeosporioides and its quinone outside inhibitor-resistant mutants. The LAMP assay for detection of C. gloeosporioides in strawberry plants has great potential for rapid strawberry anthracnose surveillance and will provide farmers with advice on preventing C gloeosporioides at the early stages of strawberry development.


Assuntos
Agricultura , Colletotrichum , Farmacorresistência Fúngica , Fragaria , Técnicas de Amplificação de Ácido Nucleico , Agricultura/métodos , Antifúngicos/farmacologia , China , Colletotrichum/efeitos dos fármacos , Colletotrichum/genética , Farmacorresistência Fúngica/genética , Fragaria/microbiologia , Doenças das Plantas/microbiologia , Estrobilurinas/farmacologia
8.
Chemosphere ; 226: 36-46, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30913426

RESUMO

In this study, fenamidone, propamocarb and their transformation products were monitored in cherry tomato, cucumber, and courgette samples. A mixture of both compounds, which have different physico-chemical characteristics, are commercially available (Consento®). For analysis, ultra high-performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) and gas chromatography coupled to Q-Orbitrap mass spectrometry (GC-Q-Orbitrap-MS) were used. The dissipation of these active ingredients was monitored at two doses (normal and double dose) from 1 to 40 days after the application of the commercial product. Half-lives (DT50) were lower than 30 days for both compounds, which indicates low persistence. Metabolites of both compounds were also monitored due to in some cases these can be more dangerous for human health than the parent compounds. The metabolites monitored were RPA 410193 ((5S)-3-anilino-5-methyl-5-phenylimidazolidine-2,4-dione), acetophenone, 2-phenylpropionic acid, 5-methyl-5-phenylhydantoin and 5-methylhydantoin for fenamidone, and propamocarb hydrochloride (propyl 3-(dimethylamino)propylcarbamate hydrochloride), N-oxide propamocarb (propyl [3-(dimethylnitroryl)propyl]carbamate), oxazoline-2-one propamocarb (3-[3-(dimethylamino)propyl]-4-hydroxy-4-methyl-1,3-oxazolidin-2-one), 2-hydroxypropamocarb and n-desmethyl propamocarb (propyl [3-(methylamino)propyl]carbamate) for propamocarb. In addition, they were detected one day after the application of commercial product, being RPA 410193, the metabolite detected at the highest concentration in samples. Retrospective analysis of incurred samples allowed putative identification of four possible new metabolites of propamocarb and one of fenamidone.


Assuntos
Carbamatos/uso terapêutico , Cromatografia Líquida de Alta Pressão/métodos , Fungicidas Industriais/uso terapêutico , Cromatografia Gasosa-Espectrometria de Massas/métodos , Estrobilurinas/uso terapêutico , Verduras/química , Carbamatos/farmacologia , Fungicidas Industriais/farmacologia , Humanos , Cinética , Estudos Retrospectivos , Estrobilurinas/farmacologia
9.
Plant Dis ; 103(5): 841-845, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30806573

RESUMO

The quinone outside inhibitor (QoI) fungicides are known for their inherently high resistance risk owing to substitutions in amino acid residues 129, 137, or 143 of the cytochrome b gene of phytopathogens. In Venturia effusa, cause of pecan scab, an intron adjacent to position 143 likely reduces this risk; however, the effects of a recently discovered substitution at position 137 (G137S) are unknown. Traditional in vitro assays are not useful for determining sensitivity of isolates of V. effusa to the QoI fungicides, owing to the fungitoxic effects of required alternative oxidase inhibitors. A detached leaf assay was developed to quantify the sensitivity of 59 isolates to azoxystrobin: 45 wild-type isolates and 14 carrying G137S. Isolate EC50 values ranged from <0.0001 to 0.3047 µg/ml; EC50 values for wild-type isolates ranged from <0.0001 to 0.2007 µg/ml (median 0.0023 µg/ml), whereas EC50 values for G137S isolates ranged from 0.0033 to 0.3047 µg/ml (median 0.0178 µg/ml). The median EC50 value for G137S isolates was significantly greater than that of the wild-type isolates; however, there was overlap between the two groups. This is the first report of sensitivity of V. effusa isolates to a QoI fungicide and evidence of G137S as a potential mechanism of partial resistance. However, although a complete control failure is unlikely, the impact of this substitution on QoI efficacy in Georgia pecan orchards remains to be determined.


Assuntos
Substituição de Aminoácidos , Ascomicetos , Pirimidinas , Estrobilurinas , Ascomicetos/efeitos dos fármacos , Ascomicetos/genética , Complexo III da Cadeia de Transporte de Elétrons/química , Complexo III da Cadeia de Transporte de Elétrons/genética , Fungicidas Industriais/farmacologia , Georgia , Testes de Sensibilidade Microbiana , Folhas de Planta/microbiologia , Pirimidinas/farmacologia , Estrobilurinas/farmacologia
10.
Chem Biol Interact ; 300: 35-39, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30629953

RESUMO

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.


Assuntos
Fungicidas Industriais/farmacologia , Pirimidinas/farmacologia , Estrobilurinas/farmacologia , Animais , Cálcio/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Masculino , Potenciais da Membrana/efeitos dos fármacos , Canais de Potássio Cálcio-Ativados/antagonistas & inibidores , Canais de Potássio Cálcio-Ativados/metabolismo , Quinina/farmacologia , Ratos , Ratos Wistar , Timócitos/citologia , Timócitos/efeitos dos fármacos , Timócitos/metabolismo
11.
PLoS One ; 13(12): e0208353, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30562344

RESUMO

Late wilt, a disease severely affecting maize fields throughout Israel, is characterized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. The disease's causal agent is the fungus Harpophora maydis, a soil-borne and seed-borne pathogen, which is currently controlled using reduced sensitivity maize cultivars. In a former study, we showed that Azoxystrobin (AS) injected into a drip irrigation line assigned for each row can suppress H. maydis in the field and that AS seed coating can provide an additional layer of protection. In the present study, we examine a more cost-effective protective treatment using this fungicide with Difenoconazole mixture (AS+DC), or Fluazinam, or Fluopyram and Trifloxystrobin mixture, or Prothioconazole and Tebuconazole mixture in combined treatment of seed coating and a drip irrigation line for two coupling rows. A recently developed Real-Time PCR method revealed that protecting the plants using AS+DC seed coating alone managed to delay pathogen DNA spread in the maize tissues, in the early stages of the growth season (up to the age of 50 days from sowing), but was less effective in protecting the crops later. AS+DC seed coating combined with drip irrigation using AS+DC was the most successful treatment, and in the double-row cultivation, it reduced fungal DNA in the host tissues to near zero levels. This treatment minimized the development of wilt symptoms by 41% and recovered cob yield by a factor of 1.6 (to the level common in healthy fields). Moreover, the yield classified as A class (cob weight of more than 250 g) increased from 58% to 75% in this treatment. This successful treatment against H. maydis in Israel can now be applied in vast areas to protect sensitive maize cultivars against maize late wilt disease.


Assuntos
Antifúngicos/farmacologia , Ascomicetos/efeitos dos fármacos , Ascomicetos/patogenicidade , Zea mays/microbiologia , Acetatos/farmacologia , Benzamidas/farmacologia , Dioxolanos/farmacologia , Iminas/farmacologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Piridinas/farmacologia , Estrobilurinas/farmacologia , Triazóis/farmacologia
12.
World J Microbiol Biotechnol ; 34(9): 130, 2018 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-30101403

RESUMO

Chili pepper (Capsicum annum L.) is an important economic crop that is severely destroyed by the filamentous oomycete Phytophthora capsici. Little is known about this pathogen in key chili pepper farms in Punjab province, Pakistan. We investigated the genetic diversity of P. capsici strains using standard taxonomic and molecular tools, and characterized their colony growth patterns as well as their disease severity on chili pepper plants under the greenhouse conditions. Phylogenetic analysis based on ribosomal DNA (rDNA), ß-tubulin and translation elongation factor 1α loci revealed divergent evolution in the population structure of P. capsici isolates. The mean oospore diameter of mating type A1 isolates was greater than that of mating type A2 isolates. We provide first evidence of an uneven distribution of highly virulent mating type A1 and A2 of P. capsici that are insensitive to mefenoxam, pyrimorph, dimethomorph, and azoxystrobin fungicides, and represent a risk factor that could ease outpacing the current P. capsici management strategies.


Assuntos
Capsicum/microbiologia , Genes Fúngicos Tipo Acasalamento/genética , Variação Genética , Phytophthora/classificação , Phytophthora/genética , Acrilamidas/farmacologia , Alanina/análogos & derivados , Alanina/farmacologia , Análise por Conglomerados , DNA Ribossômico/genética , Resistência a Medicamentos , Evolução Molecular , Fungicidas Industriais/farmacologia , Morfolinas/farmacologia , Paquistão , Elongação Traducional da Cadeia Peptídica/genética , Fenótipo , Filogenia , Phytophthora/efeitos dos fármacos , Phytophthora/isolamento & purificação , Doenças das Plantas/microbiologia , Raízes de Plantas/parasitologia , Pirimidinas/farmacologia , Fatores de Risco , Esporângios/citologia , Estrobilurinas/farmacologia , Temperatura Ambiente , Tubulina (Proteína)/genética , Virulência
13.
Ecotoxicol Environ Saf ; 162: 77-84, 2018 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-29990742

RESUMO

Crop protection agents are widely used in modern agriculture and exert direct effects on non-target microorganisms such as yeasts. Yeasts abundantly colonize wheat grain and affect its chemical composition. They can also limit pathogen growth. This study evaluated the sensitivity of yeast communities colonizing winter wheat kernels to benzimidazole, strobilurin, triazole and morpholine fungicides, trinexapac-ethyl, a commercial mixture of o-nitrophenol+p-nitrophenol+5-nitroguaiacol, and chitosan applied during the growing season of winter wheat and in vitro in a diffusion test. A molecular identification analysis of yeasts isolated from winter wheat kernels was performed, and nucleotide polymorphisms in the CYTb gene (G143A) conferring resistance to strobilurin fungicides in yeast cells were identified. The size of yeast communities increased during grain storage, and the total counts of endophytic yeasts were significantly (85%) reduced following intensive fungicide treatment (fenpropimorph, a commercial mixture of pyraclostrobin, epoxiconazole and thiophanate-methyl). This study demonstrated that agrochemical residues in wheat grain can drive selection of yeast communities for reduced sensitivity to xenobiotics. A mutation in the CYTb gene (G143A) was observed in all analyzed isolates of the following azoxystrobin-resistant species: Aureobasidium pullulans, Debaryomyces hansenii, Candida albicans and C. sake. Agrochemicals tested in vitro were divided into four classes of toxicity to yeasts: (1) tebuconazole and a commercial mixture of flusilazole and carbendazim - most toxic to yeasts; (2) fenpropimorph and a commercial mixture of pyraclostrobin and epoxyconazole; (3) propiconazole, chitosan, thiophanate-methyl and a commercial mixture of o-nitrophenol, p-nitrophenol and 5-nitroguaiacol; (4) trinexapac-ethyl and azoxystrobin - least toxic to yeasts. It was found that agrochemicals can have an adverse effect on yeast abundance and the composition of yeast communities, mostly due to differences in fungicide resistance between yeast species, including the clinically significant C. albicans.


Assuntos
Agroquímicos/farmacologia , Farmacorresistência Fúngica/genética , Fungicidas Industriais/farmacologia , Triticum/microbiologia , Leveduras/efeitos dos fármacos , Leveduras/genética , Agaricales/efeitos dos fármacos , Agaricales/genética , Ascomicetos/efeitos dos fármacos , Ascomicetos/genética , Benzimidazóis/farmacologia , Candida albicans/efeitos dos fármacos , Candida albicans/genética , Carbamatos/farmacologia , Compostos de Epóxi/farmacologia , Testes de Sensibilidade Microbiana , Resíduos de Praguicidas/análise , Doenças das Plantas/microbiologia , Pirimidinas/farmacologia , Estações do Ano , Silanos/farmacologia , Estrobilurinas/farmacologia , Triazóis/farmacologia , Xenobióticos/farmacologia , Leveduras/classificação
14.
J Agric Food Chem ; 66(21): 5335-5345, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29741370

RESUMO

A series of dithioacetal derivatives bearing a strobilurin moiety were designed and synthesized on the basis of our previous work. The antiviral activities of these compounds against Potato virus Y (PVY), Cucumber mosaic virus (CMV), and Tobacco mosaic virus (TMV) were systematically evaluated. Bioassay results indicated that C14 elicited excellent curative and protective activities against PVY, CMV, and TMV. The former had 50% effective concentrations (EC50) of 125.3, 108.9, and 181.7 µg/mL, respectively, and the latter had 148.4, 113.2, and 214.6 µg/mL, respectively, which were significantly superior to those of lead compound 6f (297.6, 259.6, and 582.4 µg/mL and 281.5, 244.3, and 546.3 µg/mL, respectively), Ningnanmycin (440.5, 549.1, and 373.8 µg/mL and 425.3, 513.3, and 242.7 µg/mL, respectively), Chitosan oligosaccharide (553.4, 582.8, and 513.8 µg/mL and 547.3, 570.6, and 507.9 µg/mL, respectively), and Ribavirin (677.4, 690.3, and 686.5 µg/mL and 652.7, 665.4, and 653.4 µg/mL, respectively). Moreover, defensive enzyme activities and RT-qPCR analysis demonstrated that the antiviral activity was associated with the changes of SOD, CAT, and POD activities in tobacco, which was proved by the related proteins of abscisic acid signaling pathway. This work provided a basis for further design, structural modification, and development of dithioacetal derivatives as new antiviral agents.


Assuntos
Acetais/química , Antivirais/farmacologia , Doenças das Plantas/virologia , Vírus de Plantas/efeitos dos fármacos , Estrobilurinas/farmacologia , Acetais/farmacologia , Antivirais/química , Clorofila/análise , Cucumovirus/efeitos dos fármacos , Doenças das Plantas/prevenção & controle , Folhas de Planta/virologia , Potyvirus/efeitos dos fármacos , Estrobilurinas/química , Tabaco/virologia , Vírus do Mosaico do Tabaco/efeitos dos fármacos
15.
Chemosphere ; 207: 573-580, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29843034

RESUMO

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.


Assuntos
Desenvolvimento Embrionário/efeitos dos fármacos , Fungicidas Industriais/uso terapêutico , Fígado/patologia , Pirimidinas/uso terapêutico , Estrobilurinas/uso terapêutico , Poluentes Químicos da Água/efeitos adversos , Peixe-Zebra/embriologia , Animais , Feminino , Fungicidas Industriais/farmacologia , Masculino , Estresse Oxidativo , Pirimidinas/farmacologia , Estrobilurinas/farmacologia
16.
Bioorg Med Chem ; 26(4): 875-883, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29395803

RESUMO

A series of novel pyraclostrobin derivatives were designed and prepared as antifungal agents. Their antifungal activities were tested in vitro with five important phytopathogenic fungi, namely, Batrylis cinerea, Phytophthora capsici, Fusarium sulphureum, Gloeosporium pestis and Sclerotinia sclerotiorum using the mycelium growth inhibition method. Among these compounds, 5s displayed IC50 value of 0.57 µg/mL against Batrylis cinerea and 5k-II displayed IC50 value of 0.43 µg/mL against Sclerotinia sclerotiorum, which were close to that of the positive control pyraclostrobin (0.18 µg/mL and 0.15 µg/mL). Other compounds 5f, 5k-II, 5j, 5m and 5s also exhibited strong antifungal activity. Further enzymatic assay demonstrated compound 5s inhibited porcine bc1 complex with IC50 value of 0.95 µM. The statistical results from an integrated computational pipeline demonstrated the predicted total binding free energy for compound 5s is the highest. Consequently, compound 5s with the biphenyl-4-methoxyl side chain could serve as a new motif as inhibitors of bc1 complex and deserve to be further investigated.


Assuntos
Antifúngicos/síntese química , Desenho de Drogas , Estrobilurinas/química , Antifúngicos/química , Antifúngicos/farmacologia , Sítios de Ligação , Complexo III da Cadeia de Transporte de Elétrons/química , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Fungos/efeitos dos fármacos , Fusarium/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Estrutura Terciária de Proteína , Estrobilurinas/síntese química , Estrobilurinas/farmacologia , Relação Estrutura-Atividade , Termodinâmica
17.
Phytopathology ; 108(4): 462-468, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29135359

RESUMO

Quinone-outside inhibitor (QoI) fungicides are used to manage anthracnose of strawberry, caused by Colletotrichum acutatum. However, selection for resistance to QoI fungicides was first reported in 2013 in Florida and, subsequently, in strawberry nurseries and production areas across the United States and Canada. C. acutatum resistance to QoIs is associated with the G143A point mutation in the cytochrome b gene. This mutation is known to be associated with field resistance even at high rates of QoI. In this study, we investigated the relative fitness and competitive ability of QoI-resistant and -sensitive C. acutatum isolates. A fitness comparison did not indicate any difference between resistant and sensitive isolates in aggressiveness, spore production, and mycelial growth at different temperatures. Additionally, in the absence of selection pressure, resistant and sensitive isolates were equally competitive. Cultivation of QoI-resistant and QoI-sensitive isolates for four culture cycles in vitro in the absence of azoxystrobin showed that QoI resistance was stable. The observed lack of fitness penalties and stability of the G143A mutation in QoI-resistant C. acutatum populations suggest that the interruption and further reintroduction of QoI fungicides might not be an option for strawberry nurseries and fruit production areas. Further investigation of alternative chemical and nonchemical C. acutatum control practices, in addition to the integration of multisite fungicides, is needed to reduce the occurrence and distribution of QoI-resistant populations in strawberry fields.


Assuntos
Colletotrichum/fisiologia , Citocromos b/genética , Farmacorresistência Fúngica/genética , Fragaria/microbiologia , Doenças das Plantas/microbiologia , Pirimidinas/farmacologia , Estrobilurinas/farmacologia , Substituição de Aminoácidos , Canadá , Colletotrichum/efeitos dos fármacos , Colletotrichum/genética , Florida , Frutas/efeitos dos fármacos , Proteínas Fúngicas/genética , Fungicidas Industriais/farmacologia , Genótipo , Mutação Puntual
18.
Environ Sci Pollut Res Int ; 25(1): 469-478, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29043591

RESUMO

The saprotrophic fungus Alternaria alternata is widespread in the agro-environment and produces more than ten allergenic proteins, mostly protein Alt a 1. The frequency of the Alt a 1 gene was analyzed in a group of A. alternata isolates from winter wheat kernels obtained in Poland, and the effectiveness of various fungicides targeting the pathogen was evaluated. The Alt a 1 gene was identified in four of the seven tested isolates. A. alternata colonized 35.67% kernels on average, but its frequency increased in stored grain where the presence of epiphytes was noted on 23.09 to 51.38% kernels, and endophytes-in 26.21 to 42.01% of kernels. The efficacy of field-applied fungicides did not exceed 50%, despite the fact that A. alternata is highly sensitive to propiconazole, fenpropimorph, and tebuconazole under in vitro conditions. The analyzed isolates were characterized by limited sensitivity to azoxystrobin (EC50 ranged from 0.505 to 1.350 µg cm-3) due to a mutation at codon 143 of the CYT b gene, responsible for resistance to quinone outside inhibitor fungicides, which was noted in all isolates. The spread of A. alternata can be effectively controlled with suitable fungicides and by monitoring the prevalence of pathogenic isolates in the environment.


Assuntos
Alérgenos/genética , Alternaria/genética , Citocromos b/genética , Fungicidas Industriais/farmacologia , Mutação , Pirimidinas/farmacologia , Estrobilurinas/farmacologia , Alérgenos/efeitos dos fármacos , Alérgenos/isolamento & purificação , Alternaria/efeitos dos fármacos , Alternaria/isolamento & purificação , Farmacorresistência Fúngica , Polônia , Triticum/microbiologia
19.
Pest Manag Sci ; 74(2): 302-313, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28881414

RESUMO

BACKGROUND: Insensitivity of Zymoseptoria tritici to demethylation inhibitor (DMI) and quinone outside inhibitor (QoI) fungicides has been widely reported from laboratory studies, but the relationships between laboratory sensitivity phenotype or target site genotype and field efficacy remain uncertain. This article reports field experiments quantifying dose-response curves, and investigates the relationships between field performance and in vitro half maximal effective concentration (EC50 ) values for DMIs, and the frequency of the G143A substitution conferring QoI resistance. RESULTS: Data were analysed from 83 field experiments over 21 years. Response curves were fitted, expressed as percentage control, rising towards an asymptote with increasing dose. Decline in DMI efficacy over years was associated with a decrease in the asymptote, and reduced curvature. Field ED50 values were positively related to in vitro EC50 values for isolates of Z. tritici collected over a 14-year period. Loss of QoI efficacy was expressed through a change in asymptote. Increasing frequency of G143A was associated with changes in field dose-response asymptotes. CONCLUSION: New resistant strains are often detected by resistance monitoring and laboratory phenotyped/genotyped before changes in field performance are detected. The relationships demonstrated here between laboratory tests and field performance could aid translation between laboratory and field for other fungicide groups. © 2017 Society of Chemical Industry.


Assuntos
Ascomicetos/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Doenças das Plantas/prevenção & controle , Estrobilurinas/farmacologia , Ascomicetos/genética , Desmetilação , Relação Dose-Resposta a Droga , Fungicidas Industriais/química , Genótipo , Fenótipo , Estrobilurinas/química
20.
Plant Dis ; 102(2): 349-358, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30673534

RESUMO

The application of succinate dehydrogenase inhibiting (SDHI) and quinone outside inhibiting (QoI) fungicide chemistries is a primary tactic in the management of early blight of potato, caused by Alternaria solani. Resistance to QoIs in A. solani has been attributed to the F129L mutation, while resistance to SDHIs is conferred by five different known point mutations on three AsSdh genes. In total, 1,323 isolates were collected from 2013 through 2015 across 11 states to determine spatial and temporal frequency distribution of these mutations. A real-time polymerase chain reaction (PCR) was used to detect the presence of the F129L mutation. Molecular detection of SDHI-resistant isolates was performed using SDH multiplex PCR specific for point mutations in AsSdhB, AsSdhC, or AsSdhD genes and mismatch amplification analysis PCR detecting the point mutations in AsSdhB. Previous work in our research group determined that substitutions of histidine for tyrosine (H278Y) or arginine (H278R) at codon 278 on the AsSdhB gene were the most prevalent mutations, detected in 46 and 21% of A. solani isolates, respectively, collected in 2011 to 2012, and uniformly distributed among six sampled states. In contrast, the substitution of histidine for arginine (H134R) at codon 134 in the AsSdhC gene was the most prevalent mutation in 2013 through 2015, identified in 36% of isolates, compared with 7.5% of isolates recovered in 2011 to 2012. Substitutions of histidine for arginine (H133R) at codon 133 and aspartic acid for glutamic acid (D123E) at codon 123 in the AsSdhD gene were detected in 16 and 12%, respectively, in the A. solani population by 2015 and were recovered across a wide range of states, compared with 15 and 1.5% of isolates collected in 2011 to 2012, respectively. Overall, SDHI- and QoI-resistant isolates were detected at high frequencies across all years, with evidence of significant spatial variability. Future research will investigate whether these results are due to differences in parasitic fitness.


Assuntos
Alternaria/genética , Farmacorresistência Fúngica , Proteínas Fúngicas/genética , Fungicidas Industriais/farmacologia , Alternaria/efeitos dos fármacos , Reação em Cadeia da Polimerase Multiplex , Mutação , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Solanum tuberosum/microbiologia , Estrobilurinas/farmacologia , Succinato Desidrogenase/antagonistas & inibidores , Estados Unidos
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