133 resultados para Phytophthora nicotianae
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Phylogenetic analysis through morphological and cultural traits is considered inconsistent and hard to be scientifically accepted once there is no way to establish the direction of evolution on morphological traits. Molecular markers are suitable for phylogenetic analysis. The sequencing of ITS1 and ITS2 (internal transcribed spacers) regions and of 5.8S gene from ribosomal DNA were used to estimate the genetic variation and distance of 10 Phytophthora capsici isolates. The amount of genetic variation amongst isolated P. capsici from distinct regions of São Paulo State was 0.1 to 1.6 and 0.1 to 1.1% at ITS1 and ITS2, respectively, and a phylogenetic distance of about 78.5% between P. capsici and Phytophthora spp. was observed.
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Pós-graduação em Agronomia (Horticultura) - FCA
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Agronomia (Proteção de Plantas) - FCA
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC
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Inoculum sources and Preservation in Soils of Phytophthora parasitica from Cherry Tomato in Continental Crop Areas in Southeast Spain
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Phytophthora infestans causes severe symptoms of wilt disease on potato crops (Solanum tuberosum) in the Toluca Valley (Mexico)despite the use of fungicides. P. infestans oospores produced by sexual reproduction can survive in the soil for many years, resisting harsh environments.
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We have investigated the role of the isoflavones daidzein and genistein on the chemotropic behavior of germinating cysts of Phytophthora sojae. Hyphal germlings were shown to respond chemotropically to daidzein and genistein, suggesting that hyphal tips from zoospores that have encysted adjacent to the root may use specific host isoflavones to locate their host. Observations of the contact response of hyphal germlings were made on several different substrates in the presence and absence of isoflavones. Hyphal tips of germlings detected and penetrated pores in membranes and produced multiple appressoria on smooth, impenetrable surfaces. Hyphae that successfully penetrated the synthetic membrane were observed to grow away from the membrane surface. The presence of isoflavones in the medium surrounding the hyphal germlings did not appear to alter any of those habits. Daidzein and genistein did not inhibit germination or initial hyphal growth at concentrations up to 20 μm.
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Elicitins are a family of small proteins secreted by species of Phytophthora. They are thought to be major determinants of the resistance response of tobacco against these oomycetes, since purified elicitins, alone and at low concentrations, can induce vigorous defense responses in tobacco (i.e., hypersensitive cell death and resistance against subsequent pathogen attack), and in vitro elicitin production by Phytophthora isolates is strongly negatively correlated with their pathogenicity on tobacco plants. A number of elicitins have been purified and their amino acid sequences have been determined and found to be conserved. A three-dimensional structure for elicitin is emerging from nuclear magnetic resonance studies. Two structural classes, alpha and beta, are distinguished by their biological effects when applied to decapitated stems or petioles; the beta class causes more necrosis on leaves and provides better subsequent protection against pathogen attack. However, both these classes of elicitins will similarly cause necrosis when each is, instead, directly infiltrated into tobacco leaf panels. Effects of elicitins on tobacco cells include rapid electrolyte leakage, changes in protein phosphorylation and amounts of active oxygen species, and later production of ethylene and capsidiol. The sites of initial interaction with tobacco cells are unknown, but the interaction appears to induce general defense-related responses.
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Mode of access: Internet.
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Mode of access: Internet.
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Diss. - Vienna.
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Mode of access: Internet.
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Mode of access: Internet.