896 resultados para Pathogenic fungi
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Pós-graduação em Medicina Veterinária - FMVZ
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Química - IQ
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The Tahiti lime appears very susceptible to attack by post-harvest diseases, primarily by the fungi Penicillium and Phomopsis, and also because of its high sensitivity to storage at low temperatures. In order to reduce such damage, the present study aimed to verify the efficiency of heat treatment and disinfection of pathogens in the prevention of post-harvest chilling injury of this cultivar and to compare this treatment with other products using the conventional fungicides. The heat treatments were studied with hot-water temperatures ranging between 48 and 56° C. Water at room temperature was used as a control treatment. After treatment, the fruits were kept under cold temperature at 10° C and RH 90% for about 45 days. For comparison, three other treatments were carried out simultaneously, one using imazalil, one with baking soda, and a third with sodium carbonate, these three products being applied by baths in cold water. Two groups of fruit were evaluated, one treated by immersion considering pathogens coming from the field and another by inoculation with spores of the previously isolated pathogens. For the evaluation of physical and chemical parameters of fruits, determinations were made of the skin color, texture, weight loss, size, juice yield, soluble solids, total acidity and vitamin C content. The determination of the sensitivity of the fruit to cold was made by their exposure at temperatures inducing cold damage. The design was a randomized block design with nine treatments, analyzed by the Statgraphics statistical package. Heat treatments, especially at 52° C, were shown to be more promising in the control of pathogenic fungi and cold damage, surpassing the conventional fungicides. No changes were found in the intrinsic and extrinsic parameters in relation to the application of the different treatments.
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Pinus taeda is one of the main timber trees in Brazil, occupying 1.8 million ha with an annual productivity of 25-30 m(3) ha(-1). Another important species is Araucaria angustifolia, belonging to the fragile Rainforest biome, which for decades has been a major source of timber in Brazil. Some diseases that affect the roots and/or the stem of these trees and cause "damping-off" of the seedlings, with economic and environmental losses for the forest sector, are caused by the plant pathogenic fungi Fusarium sp. or Armillaria sp. This research project intended to isolate actinobacteria from the Araucaria rhizosphere, which present an antagonistic effect against these fungi. After the selection of the best pathogen inhibitors, morphologic characteristics, enzyme production, and their effect on the growth of Pinus taeda were studied. The actinobacteria were tested for their antagonistic capacity against Fusarium sp. in Petri plates with PDA as substrate. The inhibition zone was measured after 3, 5, 7, and 10 days. Of all the isolates tested, only two of them maintained inhibition zones up to 4 mm for 10 days. The inhibition of Armillaria sp. was tested in liquid medium and also in Petri dishes through the evaluation of the number of the fungal rhizomorphs in dual culture with the actinobacteria. It was found that all five isolates were able to inhibit the rhizomorph production, with the best performance of the isolate A43, which was capable of inhibiting both fungi, Fusarium and Armillaria. In a greenhouse experiment, the effect of five isolates on the growth of Pinus taeda seedlings was tested. Plant height, stem diameter, root and shoot dry matter were determined. The Streptomyces isolate A43 doubled plant growth. These results may lead to the development of new technologies in the identification of still unknown bacterial metabolites and new management techniques to control forest plant diseases.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Brazilian populations of the pathogenic fungus Neozygites floridana (Weiser & Muma) Remaudiere & S. Keller (Entomophthoromycotina: Entomophthorales) and the predatory mite Phytoseiulus longipes Evans (Acari: Phytoseiidae) are potential candidates for introduction into Africa for classical biological control of the tomato red spider mite, Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae). The efficiency of these natural enemies against T. evansi has been demonstrated under laboratory conditions, but little is known about their performance on native Solanaceae in the field. The American nightshade, Solanum americanum Mill., is native to the Americas and may serve as an alternative host plant for T. evansi and its natural enemies in the absence of tomato plants. In this work, we studied the population dynamics of T. evansi and its natural enemies on S. americanum in a screen house, semi-field and field plots in Recife, Pernambuco, Brazil, to evaluate the potential of natural enemies for controlling T. evansi. Of the four natural enemies found in association with T. evansi, only N. floridana and P. longipes were clearly associated with the reduction of the populations of T. evansi. Neozygites floridana was observed in a screen house, semi-field and field plots, but P. longipes was only detected in the semi-field plots. Increases in the population of T. evansi were always followed by increases in the density of one of these natural enemies, suggesting that they were important factors regulating T. evansi populations on S. americanum. The presence of this host plant near the release sites in Africa thus might increase the chances for the permanent establishment of these natural enemies.
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A survey of Microsporum gypseum was conducted in soil samples in different geographical regions of Brazil. The isolation of dermatophyte from soil samples was performed by hair baiting technique and the species were identified by morphology studies. We analyzed 692 soil samples and the recuperating rate was 19.2%. The activities of keratinase and elastase were quantitatively performed in 138 samples. The sequencing of the ITS region of rDNA was performed in representatives samples. M. gypseum isolates showed significant quantitative differences in the expression of both keratinase and elastase, but no significant correlation was observed between these enzymes. The sequencing of the representative samples revealed the presence of two teleomorphic species of M. gypseum (Arthroderma gypseum and A. incurvatum). The enzymatic activities may play an important role in the pathogenicity and a probable adaptation of this fungus to the animal parasitism. Using the phenotypical and molecular analysis, the Microsporum identification and their teleomorphic states will provide a useful and reliable identification system.