Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.296
Filtrar
1.
J Agric Food Chem ; 67(38): 10646-10652, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31479255

RESUMO

A new monosesquiterpene diacetylgliocladic acid (1), a new dimeric sesquiterpene divirensol H (9), and two exceptionally novel trimeric sesquiterpene trivirensols A and B (11 and 12), together with another eight known congeners, were purified from an endophytic fungus Trichoderma virens FY06, derived from Litchi chinensis Sonn. whose fruit is a delicious and popular food. All of them were identified by comprehensive spectroscopic analysis, combined with biosynthetic considerations. Trivirensols A and B are unprecedented trimers of which three subunits are connected by two ester bonds of the sesquiterpene class. Relative to the positive control triadimefon, all the tested metabolites showed strong inhibitory activities against at least one phytopathogenic fungus among Penicillium italicum, Fusarium oxysporum, Fusarium graminearum, Colletotrichum musae, and Colletotrictum gloeosporioides. Notably, as metabolites of the endophytic fungus from L. chinensis, they all presented strong antifungal activities against C. gloeosporioides which causes anthracnose in L. chinensis.


Assuntos
Fungicidas Industriais/farmacologia , Litchi/microbiologia , Sesquiterpenos/farmacologia , Trichoderma/química , Colletotrichum/efeitos dos fármacos , Colletotrichum/crescimento & desenvolvimento , Endófitos/química , Endófitos/genética , Endófitos/isolamento & purificação , Endófitos/metabolismo , Frutas/microbiologia , Fungicidas Industriais/química , Fungicidas Industriais/metabolismo , Fusarium/efeitos dos fármacos , Fusarium/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Doenças das Plantas/microbiologia , Sesquiterpenos/química , Sesquiterpenos/metabolismo , Trichoderma/genética , Trichoderma/isolamento & purificação
2.
J Agric Food Chem ; 67(38): 10782-10790, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31490683

RESUMO

Systematic investigation of cyproconazole, including absolute stereochemistry, fungicidal activity, quantification in two matrixes, and stereoselective degradation in cucumber, are conducted in this study. By virtue of vibrational circular dichroism (VCD) spectroscopy, absolute configurations of four stereoisomers were identified to be (2R,3R)-(+)-, (2R,3S)-(+)-, (2S,3S)-(-)-, and (2S,3R)-(-)-cyproconazoles. Then four stereoisomers exhibited stereoselective fungicidal activities against Fusarium graminearum Schw and Magnaporthe oryzae, and the order of fungicidal activity was (2S,3S)-(-)-stereoisomer > the stereoisomer mixture > (2S,3R)-(-)-stereoisomer > (2R,3R)-(+)-stereoisomer > (2R,3S)-(+)-stereoisomer. Moreover, chiral liquid chromatography-tandem mass spectrometry was used to identify and quantify cyproconazole stereoisomers in soil and cucumber matrixes. Good linearity (R2 ≥ 0.99) and recoveries (86.79-92.47%, RSD ≤ 3.94%) for them were achieved, individually. Furthermore, stereoselective degradation of four cyproconazole stereoisomers was observed in cucumber and the order of degradation rate was (2R,3R)-(+)-cyproconazole > (2S,3S)-(-)-cyproconazole > (2R,3S)-(+)-cyproconazole > (2S,3R)-(-)-cyproconazole. We envision that such systematic assessments of chiral fungicides at an enantiomeric level would provide valuable information in future studies involving enantioselective physiological, metabolic, and toxicological activities.


Assuntos
Fungicidas Industriais/química , Triazóis/química , Alternaria/efeitos dos fármacos , Alternaria/crescimento & desenvolvimento , Cromatografia Líquida de Alta Pressão , Cucumis sativus/química , Contaminação de Alimentos/análise , Fungicidas Industriais/farmacologia , Fusarium/efeitos dos fármacos , Fusarium/crescimento & desenvolvimento , Rhizoctonia/efeitos dos fármacos , Rhizoctonia/crescimento & desenvolvimento , Poluentes do Solo/química , Poluentes do Solo/farmacologia , Estereoisomerismo , Espectrometria de Massas em Tandem , Triazóis/farmacologia
3.
Pestic Biochem Physiol ; 158: 121-127, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31378347

RESUMO

Iminoctadine tris (albesilate) is a bis-guazatine fungicide, and its specific modes of action and efficacy against C. cassiicola are not yet clear. In this study, baseline sensitivity data for mycelial growth showed that the frequency distribution curve of iminoctadine tris (albesilate) EC50 values is unimodal. The EC50 values ranged from 0.1151 to 1.2101 µg/mL, with a mean of 0.5775 ±â€¯0.2677 µg/mL. Iminoctadine tris (albesilate) affected the morphological development of C. cassiicola, causing increased branching of the mycelium. The significant increase in membrane permeability and malondialdehyde content after iminoctadine tris (albesilate) treatment indicated that this fungicide caused severe damage to the membrane structure. Furthermore, 0.4 µg/mL iminoctadine tris (albesilate) could decrease the spore density of C. cassiicola from 2.6200 × 104 to 1.4967 × 104/cm2 on average in vitro, indicating that the fungicide had great potential to reduce secondary infection with C. cassiicola in the field. Additionally, 120 µg/mL iminoctadine tris (albesilate) provided over 95% curative efficacy and 81.17% preventative efficacy on detached cucumber leaves inoculated with C. cassiicola. In field trials, iminoctadine tris (albesilate) at a dose of 120 g a.i./ha exhibited 72.92% and 80.92% control efficacy in 2017 and 2018, respectively. However, the efficacy supplied by the reference fungicide azoxystrobin at 250 g a.i./ha was only approximately 50% due to the development of fungicide resistance in C. cassiicola. Taken together, the findings above provide a solid foundation for the exploration of the action mechanisms of iminoctadine tris (albesilate) against C. cassiicola and provide overwhelming evidence for the use of iminoctadine tris (albesilate) as an excellent potential alternative fungicide in the management of cucumber Corynespora leaf spot.


Assuntos
Ascomicetos/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Guanidinas/farmacologia , Cucumis sativus/microbiologia , Folhas de Planta/microbiologia
4.
Pestic Biochem Physiol ; 158: 128-134, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31378348

RESUMO

Indoleacetic acid (IAA)-carbendazim was synthesized to assess whether this conjugate could retain the fungicidal activity of carbendazim and gain root-inducing properties upon the addition of an indoleacetic acid group. An indoor virulence test demonstrated that the conjugate retained the fungicidal activity of carbendazim towards Cylindrocladium parasiticum. The conjugate was detected in roots after soaking Ricinus communis L. leaves into a solution of the IAA-carbendazim, which confirmed its phloem mobility. The activities of the cellulase, polygalacturonase and xylanase produced by Cylindrocladium parasiticum treated with different concentrations of the conjugate were determined, and the peak activities appeared at 72 h or 96 h. More importantly, the conjugate showed the ability to promote root growth. These results revealed that indoleacetic acid-carbendazim may be useful in preventing Cylindrocladium parasiticum and other diseases.


Assuntos
Ascomicetos/efeitos dos fármacos , Benzimidazóis/farmacologia , Carbamatos/farmacologia , Fungicidas Industriais/farmacologia , Ácidos Indolacéticos/farmacologia , Celulase/metabolismo , Floema/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Poligalacturonase/metabolismo , Ricinus/efeitos dos fármacos
5.
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
6.
BMC Plant Biol ; 19(1): 371, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31438856

RESUMO

BACKGROUND: Propamocarb (PM) is one of the main pesticides used for controlling cucumber downy mildew. However, due to its volatility and internal absorption, PM can easily form pesticide residues on cucumber fruits that seriously endanger human health and pollute the environment. The breeding of new cucumber varieties with a low abundance of PM residues via genetic methods constitutes an effective strategy for reducing pesticide residues and improving cucumber safety and quality. To help elucidate the molecular mechanism resulting in a low PM residue abundance in cucumber, we used the cucumber cultivar 'D0351' (which has the lowest PM residue content) as the test material and identified genes related to low PM residue abundance through high-throughput tag-sequencing (Tag-Seq). RESULTS: CsMAPEG was constitutively expressed and showed both varietal and organizational differences. This gene was strongly expressed in 'D0351'. The expression levels of CsMAPEG in different cucumber tissues under PM stress were as follows: fruit>leaf>stem>root. CsMAPEG can respond to salicylic acid (SA), gibberellin (GA) and Corynespora cassiicola Wei (Cor) stress and thus plays an important regulatory role in plant responses to abiotic and biological stresses. The PM residue abundance in the fruits of CsMAPEG-overexpressing plants was lower than those found in antisense CsMAPEG plants and wild-type plants at all tested time points. The results revealed that CsMAPEG played a positive role in reducing the PM residue abundance. A CsMAPEG sense construct increased the contents of SOD, POD and GST in cucumber fruits, enhanced the degradation and metabolism of PM in cucumber, and thus effectively reduced the pesticide residue abundance in cucumber fruits. CONCLUSIONS: The expression patterns of CsMAPEG in cucumber cultivars with high and low pesticide residue abundances and a transgenic verification analysis showed that CsMAPEG can actively respond to PM stress and effectively reduce the PM residue abundance in cucumber fruits. The results of this study will help researchers further elucidate the mechanism responsible for a low PM residue abundance in cucumber and lay a foundation for the breeding of new agricultural cucumber varieties with low pesticide residue abundances.


Assuntos
Carbamatos/farmacologia , Cucumis sativus/genética , Fungicidas Industriais/farmacologia , Genes de Plantas , Resíduos de Praguicidas , Clonagem Molecular , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/enzimologia , Cucumis sativus/fisiologia , Perfilação da Expressão Gênica , Vetores Genéticos , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transformação Genética
7.
Plant Dis ; 103(10): 2569-2576, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31398077

RESUMO

Glomerella leaf spot (GLS) and bitter rot (BR) on apples are often caused by Colletotrichum acutatum in Paraná State, Brazil. GLS control is difficult because of its rapid development, with an incubation period of only 2 days under favorable conditions. Therefore, producers use successive fungicide applications every season; however, failure to control GLS has been commonly reported. The objectives of this study were to determine the sensitivity of isolates of the C. acutatum species complex obtained from apple orchards in Brazil to mancozeb, thiophanate-methyl, and azoxystrobin fungicides. Isolates from the different parts of the plant (leaves, flowers, buds, and twigs) and cultivars (Gala and Eva) showed different levels of sensitivity to mancozeb, thiophanate-methyl, and azoxystrobin. For mancozeb, the frequencies of isolates were 25% highly resistant, 50% low-resistance, and 25% sensitive. For thiophanate-methyl, the frequencies of isolates were 72.2% highly resistant, 11.1% resistant, and 16.7% moderately resistant. For azoxystrobin, the frequencies of isolates were 11.1% highly resistant, 5.6% resistant, and 83.3% sensitive. Interestingly, no mutations in the ß-tubulin and cytochrome b genes were observed in any of the isolates resistant to thiophanate-methyl and azoxystrobin fungicides.


Assuntos
Colletotrichum , Fungicidas Industriais , Malus , Brasil , Colletotrichum/efeitos dos fármacos , Farmacorresistência Fúngica , Fungicidas Industriais/farmacologia , Malus/microbiologia , Testes de Sensibilidade Microbiana
8.
J Agric Food Chem ; 67(37): 10448-10457, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31453693

RESUMO

Carabrone is isolated from Carpesium macrocephalum Franch. et Sav, which has good fungicidal activity, especially for Gaeumannomyces graminis (Get). According to previous studies, we speculated that carabrone targets the mitochondrial enzyme complex III of Get. To elucidate the mode of action, we used carabrone to induce oxidative stress and apoptosis in Get. Incubation with carabrone reduced the burst of reactive oxygen species (ROS) and mitochondrial membrane potential, as well as phosphatidylserine release. Carabrone caused ROS accumulation in mycelia by inhibiting the activity of antioxidase enzymes, among which inhibition of glutathione reductase (GR) activity was most obvious. The catalytic center of GR consists of l-cysteine residues that react with the α-methylene-γ-butyrolactone active site of carabrone. Additionally, a positive TUNEL reaction led to diffusion of the DNA electrophoresis band and upregulation of Ggmet1 and Ggmet2. We propose that carabrone inhibits antioxidant enzymes and promotes ROS overproduction, which causes membrane hyperpermeability, release of apoptotic factors, activation of the mitochondria-mediated apoptosis pathway, and fungal cell apoptosis.


Assuntos
Apoptose/efeitos dos fármacos , Ascomicetos/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Extratos Vegetais/farmacologia , Ascomicetos/citologia , Ascomicetos/metabolismo , Asteraceae/química , Proteínas Fúngicas/metabolismo , Glutationa Redutase/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Espécies Reativas de Oxigênio/metabolismo
9.
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
10.
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
11.
Molecules ; 24(13)2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31288497

RESUMO

Fungicide is used to control fungal disease by destroying and inhibiting the fungus or fungal spores that cause the disease. However, failure to deliver fungicide to the disease region leads to ineffectiveness in the disease control. Hence, in the present study, nanotechnology has enabled the fungicide active agents (hexaconazole) to be encapsulated into chitosan nanoparticles with the aim of developing a fungicide nanodelivery system that can transport them more effectively to the target cells (Ganoderma fungus). A pathogenic fungus, Ganoderma boninense (G. boninense), is destructive to oil palm whereby it can cause significant loss to oil palm plantations located in the Southeast Asian countries, especially Malaysia and Indonesia. In regard to this matter, a series of chitosan nanoparticles loaded with the fungicide, hexaconazole, was prepared using various concentrations of crosslinking agent sodium tripolyphosphate (TPP). The resulting particle size revealed that the increase of the TPP concentration produced smaller particles. In addition, the in vitro fungicide released at pH 5.5 demonstrated that the fungicide from the nanoparticles was released in a sustainable manner with a prolonged release time up to 86 h. On another note, the in vitro antifungal studies established that smaller particle size leads to lower half maximum effective concentration (EC50) value, which indicates higher antifungal activity against G. boninense.


Assuntos
Arecaceae/microbiologia , Quitosana/química , Portadores de Fármacos/química , Fungicidas Industriais/farmacologia , Ganoderma/efeitos dos fármacos , Nanopartículas/química , Doenças das Plantas/microbiologia , Triazóis/farmacologia , Reagentes para Ligações Cruzadas/química , Liberação Controlada de Fármacos , Cinética , Tamanho da Partícula , Polifosfatos/química
12.
Plant Dis ; 103(9): 2212-2220, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31306094

RESUMO

White mold, caused by Sclerotinia sclerotiorum, is a yield-limiting disease of soybean in Brazil. Uniform fungicide trials have been conducted annually since 2009. Data from 74 cooperative field trials conducted over a 10-year period were assembled. We selected five fungicides applied two times around flowering: dimoxystrobin plus boscalid (DIMO+BOSC), carbendazim plus procymidone (CARB+PROC), fluazinam (FLUZ), fluopyram (FLUO), and procymidone (PROC). For comparison, thiophanate-methyl (TMET) applied four times was also included as a low-cost treatment. Network models were fitted to the log of white mold incidence (percentages) and log of sclerotia mass data (grams/hectare) and to the nontransformed yield data (kilograms/hectare) for each treatment, including the untreated check. Back-transformation of the meta-analytic estimates indicated that the lowest and highest mean (95% confidence interval [CI]) percent reductions in incidence and sclerotia mass were 54.2 (49.3 to 58.7) and 51.6% (43.7 to 58.3) for TMET and 83.8 (79.1 to 87.5) and 87% (81.9 to 91.6) for CARB+PROC, respectively. The overall mean (95% CI) yield responses ranged from 323 kg/ha (247.4 to 400.3) for TMET to 626 kg/ha (521.7 to 731.7) for DIMO+BOSC, but the variance was significantly reduced by a binary variable (30% threshold) describing disease incidence in the untreated check. On average, an increment of 352 kg/ha was estimated for trials where the incidence was >30% compared with the low-disease scenario. Hence, the probability of breaking even on fungicide costs for the high-disease scenario was >65% for the more effective, but more expensive fungicide (FLUZ) than TMET. For the low-disease scenario, profitability was less likely and depended more on variations in fungicide cost and soybean price.


Assuntos
Ascomicetos , Fungicidas Industriais , Doenças das Plantas , Soja , Agricultura , Ascomicetos/efeitos dos fármacos , Brasil , Fungicidas Industriais/economia , Fungicidas Industriais/farmacologia , Fungicidas Industriais/normas , Doenças das Plantas/prevenção & controle , Soja/microbiologia
13.
Plant Dis ; 103(9): 2263-2270, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322489

RESUMO

Alternaria leaf spot (ALS), caused by Alternaria spp., can occur wherever sugarbeet is grown. Infection by Alternaria spp. and disease management has historically been considered a minor issue in sugarbeet production in the United States. An increase of both incidence and severity in 2016 of ALS high enough to cause yield loss has been observed in Michigan. With a renewed need to consider potential management of this disease, the sensitivity was determined for populations of Alternaria spp. to three classes of fungicides currently labeled for management of leaf spot on sugarbeet, including demethylase inhibitor (DMI), quinone outside inhibitor (QoI), and organo-tin fungicides. Leaves with symptoms of ALS were sampled from sugarbeet fields in east-central Michigan and southwestern Ontario, Canada. Monoconidial isolates were obtained to determine sensitivity to each fungicide class above. A spiral gradient dilution method was used to estimate the fungicide effective concentration (in milligrams per liter) that caused a 50% inhibition of fungal growth in vitro for all isolates. Significant temporal shifts were detected in the frequencies of sensitivity phenotypes to DMI and QoI but not organo-tin fungicides from 2016 through 2017. Individual isolates of Alternaria spp. were recovered with cross-resistance to DMI and multiple resistance to DMI, QoI, and triphenyltin hydroxide fungicides. To our knowledge, this is the first report of a fungus other than Cercospora beticola with resistance to organo-tin fungicides. Fungicide sensitivity monitoring indicates that an effective integrated disease management approach combining fungicide efficacy trials and monitoring pathogen biology is essential for developing effective resistance management recommendations.


Assuntos
Alternaria , Beta vulgaris , Fungicidas Industriais , Alternaria/efeitos dos fármacos , Beta vulgaris/microbiologia , Farmacorresistência Fúngica , Fungicidas Industriais/farmacologia , Lagos , Michigan , Ontário , Estados Unidos
14.
Plant Dis ; 103(10): 2592-2598, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31347987

RESUMO

The objective of this study was to evaluate fungicide applications, host resistance, and trellising, alone and in combination, as management practices for downy mildew on slicing cucumber. A split-split plot experimental design was used with three and four replications in spring and fall 2017, respectively. The whole-plot treatment was fungicide, four applications of chlorothalonil (Bravo Weather Stik 6SC) alternated with three applications of cyazofamid (Ranman 400SC), or water. Split plots were nontrellised or trellised with four strings supported by stakes. Split-split plots were cultivar Bristol, which is intermediately resistant to downy mildew, or cultivar Speedway, which is susceptible to downy mildew with similar parentage as Bristol. In both seasons, area under the disease progress curve (AUDPC) values were lower with fungicides than water for both cultivars. In the spring, AUDPC for Bristol was lower than for Speedway regardless of fungicide treatment. In the fall, Bristol had a lower AUDPC than Speedway with fungicides, but the AUDPC did not differ between the two cultivars with water. The mean AUDPC for trellised plants (376.2) was lower than for nontrellised plants (434.0; P = 0.007). Fungicide applications increased marketable and total fruit weights in both seasons (P ≤ 0.0002). Marketable weight with fungicides was almost double (93% greater) the marketable weight with water. Marketable weight was 55% greater for Bristol than for Speedway in spring, but yields did not differ between cultivars in fall (season-by-cultivar interaction, P ≤ 0.0003). Because trellising had no effect on marketable yields (P = 0.11), trellising is not recommended for managing downy mildew on slicing cucumber. Of the three management techniques examined, fungicides had the largest effects on disease and yields, followed by cultivar resistance.


Assuntos
Agricultura/métodos , Cucumis sativus , Resistência à Doença , Fungicidas Industriais , Oomicetos , Cucumis sativus/microbiologia , Cucumis sativus/fisiologia , Fungicidas Industriais/farmacologia , Oomicetos/efeitos dos fármacos , Oomicetos/fisiologia , Doenças das Plantas/prevenção & controle
15.
Pestic Biochem Physiol ; 157: 33-44, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153475

RESUMO

In this work, an attempt was made to evaluate the effect of pesticides on growth pattern, surface morphology, cell viability and growth regulators of nitrogen fixing soil bacterium. Pesticide tolerant Azotobacter vinelandii strain AZ6 (Accession no. MG028654) was found to tolerate maximum level of pesticide and displayed multifarious PGP activities. At higher concentrations, pesticides triggered cellular/structural damage and reduced the cell viability as clearly shown under SEM and CLSM. With increase in concentration, pesticides exhibited a significant (p < 0.05) decrease in PGP traits of strain AZ6. Among all three groups of pesticides, herbicides glyphosate and atrazine were most toxic. Kitazin, hexaconazole, metalaxyl, glyphosate, quizalofop, atrazine, fipronil, monocrotophos and imidacloprid at 2400, 1800, 1500, 900, 1200, 900, 1800, 2100 and 2700 µg mL-1, respectively, decreased the production of IAA by 19.5 ±â€¯1.9 (61%), 18.1 ±â€¯1.2 (64%), 36.4 ±â€¯3.4 (28%), 13.1 ±â€¯0.8 (74%), 15.6 ±â€¯1.0 (69%), 7.6 ±â€¯0.5 (83%), 11.9 ±â€¯0.8 (76%), 24.7 ±â€¯1.7 (51%) and 32 ±â€¯2.3 (37%) µg mL-1, respectively, over control (50.7 ±â€¯3.6 µg mL-1). A maximum reduction of 8.4 ±â€¯1.2 (46%), 5.8 ±â€¯0.6 (62%) and 4 ±â€¯0.2 (74%) µg mL-1 in 2, 3-DHBA at 300 (1×), 600 (2×) and 900 (3×) µg mL-1 glyphosate, respectively, While, 32.8 ±â€¯2.7 (19%), 27.2 ±â€¯2 (33%) and 21.5 ±â€¯1.3 (47%) µg mL-1, respectively in the production of SA was observed at 300 (1×), 600 (2×) and 900 (3×) µg mL-1 atrazine, respectively. Likewise, with increase in concentration of pesticides, decrease in P solubilization ability and change in pH of broth was detected. The order of pesticide toxicity to PSE (percent decline over control) at highest concentration was: atrazine (45) > kitazin (44) > metalaxyl (43) > monocrotophos (43) > glyphosate (41) > hexaconazole (39) > quizalofop (33) > imidacloprid (31) > fipronil (25). The present study undoubtedly suggests that even at higher doses of pesticides, A. vinelandii maintained secreting plant growth regulators and this property makes this strain agronomically important microbe for enhancing the growth of plants.


Assuntos
Azotobacter vinelandii/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Microscopia Eletroquímica de Varredura , Reguladores de Crescimento de Planta , Rizosfera
16.
Fitoterapia ; 136: 104183, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31150767

RESUMO

Diterpenoids are the main secondary metabolites of plants and with a range of biological activities. In the present study, 7 compounds were isolated from the hulls of rice (Oryza sativa L.). Among them, 3 diterpenoids are new namely, 3,20-epoxy-3α-hydroxy- 8,11,13-abietatrie-7-one (1), 4,6-epoxy-3ß-hydroxy-9ß-pimara-7,15-diene (2) and 2-((E)-3- (4-hydroxy-3-methoxyphenyl) allylidene) momilactone A (3). While, 4 terpenoids are known, namely momilactone A (4), momilactone B (5), ent-7-oxo-kaur-15-en-18-oic acid (6) and orizaterpenoid (7). The structures of these diterpenoids were elucidated using 1D and 2D NMR in combination with ESI-MS and HR-EI-MS. Furthermore, all isolated compounds displayed antifungal activities against four crop pathogenic fungi Magnaporthe grisea, Rhizoctonia solani, Blumeria graminearum and Fusarium oxysporum, and phytotoxicity against paddy weed Echinochloa crusgalli. The results suggested that rice could produce plenty of secondary metabolites to defense against weeds and pathogens.


Assuntos
Diterpenos/farmacologia , Fungicidas Industriais/farmacologia , Herbicidas/farmacologia , Oryza/química , Sementes/química , Diterpenos/isolamento & purificação , Echinochloa/efeitos dos fármacos , Fungicidas Industriais/isolamento & purificação , Herbicidas/isolamento & purificação , Estrutura Molecular , Compostos Fitoquímicos/isolamento & purificação , Compostos Fitoquímicos/farmacologia
17.
Nat Commun ; 10(1): 2645, 2019 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-31201315

RESUMO

Lettuce downy mildew caused by Bremia lactucae is the most important disease of lettuce globally. This oomycete is highly variable and rapidly overcomes resistance genes and fungicides. The use of multiple read types results in a high-quality, near-chromosome-scale, consensus assembly. Flow cytometry plus resequencing of 30 field isolates, 37 sexual offspring, and 19 asexual derivatives from single multinucleate sporangia demonstrates a high incidence of heterokaryosis in B. lactucae. Heterokaryosis has phenotypic consequences on fitness that may include an increased sporulation rate and qualitative differences in virulence. Therefore, selection should be considered as acting on a population of nuclei within coenocytic mycelia. This provides evolutionary flexibility to the pathogen enabling rapid adaptation to different repertoires of host resistance genes and other challenges. The advantages of asexual persistence of heterokaryons may have been one of the drivers of selection that resulted in the loss of uninucleate zoospores in multiple downy mildews.


Assuntos
Núcleo Celular/genética , Interações Hospedeiro-Patógeno/genética , Alface/microbiologia , Oomicetos/genética , Doenças das Plantas/microbiologia , Núcleo Celular/efeitos dos fármacos , Resistência à Doença/genética , Fungicidas Industriais/farmacologia , Genômica , Alface/genética , Oomicetos/citologia , Oomicetos/patogenicidade , Seleção Genética/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Virulência/genética
18.
Plant Dis ; 103(8): 1884-1888, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31161931

RESUMO

It is a common practice to add salicylhydroxamic acid (SHAM) into artificial medium in the in vitro sensitivity assay of fungal phytopathogens to the quinone outside inhibitor (QoI) fungicides. The rationale for adding SHAM is to inhibit fungal alternative oxidase, which is presumed to be inhibited by secondary metabolites of plants. Therefore, the ideal characteristics of SHAM should be almost nontoxic to phytopathogens and have no significant effect on control efficacy of fungicides. However, this study showed that the average effective concentration for 50% inhibition (EC50) of mycelial growth values of SHAM were 97.5 and 401.4 µg/ml for Sclerotinia sclerotiorum and Botrytis cinerea, respectively. EC50 values of the three QoI fungicides azoxystrobin, kresoxim-methyl, and trifloxystrobin in the presence of SHAM at 20 and 80 µg/ml for S. sclerotiorum and B. cinerea, respectively, declined by 52.7 to 78.1% compared with those without SHAM. For the dicarboximide fungicide dimethachlone, the average EC50 values in the presence of SHAM declined by 18.2% (P = 0.008) for S. sclerotiorum and 35.9% (P = 0.012) for B. cinerea. Pot experiments showed that SHAM increased control efficacy of the three QoI fungicides against the two pathogens by 43 to 83%. For dimethachlone, SHAM increased control efficacy by 134% for S. sclerotiorum and 86% for B. cinerea. Biochemical studies showed that SHAM significantly inhibited peroxidase activity (P = 0.024) of B. cinerea and esterase activity (P = 0.015) of S. sclerotiorum. The strong inhibitions of SHAM per se on mycelial growth of B. cinerea and S. sclerotiorum and significant influences on the sensitivity of the two pathogens to both the QoI fungicides and dimethachlone as well as inhibitions on peroxidase and esterase indicate that SHAM should not be added in the in vitro assay of sensitivity to the QoI fungicides.


Assuntos
Ascomicetos , Botrytis , Farmacorresistência Fúngica , Fungicidas Industriais , Salicilamidas , Ascomicetos/efeitos dos fármacos , Botrytis/efeitos dos fármacos , Farmacorresistência Fúngica/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Salicilamidas/farmacologia
19.
Plant Dis ; 103(8): 1991-1997, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31169087

RESUMO

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter-1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml-1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.


Assuntos
Bacillus , Botrytis , Fungicidas Industriais , Lycopersicon esculentum , Doenças das Plantas , Bacillus/fisiologia , Botrytis/efeitos dos fármacos , Botrytis/fisiologia , Fungicidas Industriais/farmacologia , Lycopersicon esculentum/microbiologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle
20.
Plant Dis ; 103(8): 2076-2082, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31194616

RESUMO

Stem-end rot caused by Botryodiplodia theobromae is a destructive disease of mango. B. theobromae field isolates resistant to carbendazim (MBC) were collected in Hainan Province, China. In this study, the characteristics of these field isolates with resistance to MBC were investigated. The resistance of B. theobromae isolates to MBC was stably inherited. Both the MBC-resistant and MBC-sensitive isolates had similar mycelial growth rates, pathogenicity, sensitivity to high glucose, glycerol content, and peroxidase activity. Compared with MBC-sensitive isolates, MBC-resistant isolates were more sensitive to low temperature and had a significant decrease in sensitivity to high NaCl and a significant increase in catalase (CAT) and glutathione S-transferase (GST) activities. After MBC treatment, the cell membrane permeability of the sensitive isolates was markedly increased compared with that of the resistant isolates. Analysis of the ß-tubulin gene sequence revealed point mutations resulting in substitutions at codon 198 from glutamic acid (GAG) to alanine (GCG) in moderately resistant isolates, and at codon 200 from phenylalanine (TTC) to tyrosine (TAC) in highly resistant isolates. These ß-tubulin gene mutations were consistently associated with MBC resistance. Overall, we infer that the altered cell membrane permeability and the increase in CAT and GST activities of the resistant isolates are linked to MBC resistance.


Assuntos
Ascomicetos , Benzimidazóis , Carbamatos , Farmacorresistência Fúngica , Fungicidas Industriais , Ascomicetos/efeitos dos fármacos , Ascomicetos/enzimologia , Ascomicetos/genética , Ascomicetos/metabolismo , Benzimidazóis/farmacologia , Carbamatos/farmacologia , China , Farmacorresistência Fúngica/genética , Fungicidas Industriais/farmacologia , Genes Fúngicos/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA