990 resultados para Milho - Resistência aos insetos
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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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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Pós-graduação em Agronomia (Proteção de Plantas) - FCA
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Pós-graduação em Agronomia - FEIS
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Macrospora leaf spot, caused by the fungus Stenocarpella macrospora, has shown to be frequent and important among corn fields in Brazil. Genetic resistance is one of the main strategies to control corn leaf diseases. In Brazil, there is scarce information on the resistance of hybrids to Stenocarpella macrospora. The aim of this study was to evaluate the reaction of 25 corn hybrids to macrospora leaf spot. The experiment was conducted in 2011, in a greenhouse under controlled temperature and relative humidity conditions. Experimental design was completely randomized, with five replicates, each experimental unit consisting of a pot with five plants. Inoculation was done in the V2 growth stage (two fully expanded leaves), and the whorl of each plant received 2.0 mL suspension of 1.8 x 10(4) conidia mL-1 pathogen. The four used fungal isolates were obtained from infected crop residues at the municipalities Lages and Quilombo, Santa Catarina State, and Campinas do Sul and Vacaria, Rio Grande do Sul State. Disease severity was assessed at 21 days after inoculation in the V4 stage (four fully expanded leaves). No tested hybrid was totally resistant to the fungus S. macrospora. There was a significant difference in the disease severity between hybrids and fungal isolates. Hybrids inoculated with Quilombo isolate showed four reaction groups, while the isolates Vacaria, Lages and Campinas do Sul showed two groups. Some hybrids had varied behaviors against the isolates, suggesting different aggressiveness levels. There were hybrids that showed similar reaction to the isolates, suggesting greater stability for macrospora leaf spot.
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The fall armyworm Spodoptera frugiperda is one of the most important pests of maize. Various studies are conducted for their management, integrating chemical and biological control tactics as well as resistant plants. In order to offer alternatives for an efficient management of this pest with minimal use of pesticides, the technology of genetically modified plants resistant to insects has been widely studied. The aim of the present study was to evaluate the natural infestation of larvae of S. frugiperda and their injuries under field conditions in transgenic maize hybrids compared to their conventional isogenic counterparts at two sowing dates and two regions. The hybrids were planted in the off season of 2010 in Jaboticabal, SP, Brazil, and the summer of 2010/2011 in Jaboticabal, and Pindorama, SP, in a randomized block with seven treatments (hybrids) and four replications. Different levels of infestation of larvae occurred throughout the phenological development of plants in conventional and genetically modified hybrids with significant differences between the two groups in most evaluations. The hybrid 2B710HX was the least infested with caterpillars and had the least damaged leaf area. It follows that the Cry1F toxin was the most effective in protecting the plant in relation to other toxic proteins expressed by the other Bt hybrids against infestation and damage promoted by this pest, regardless of time of sowing.
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Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV
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Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Agronomia (Produção Vegetal) - FCAV
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The fall armyworm is a pest that feeds on various botanies species. The objective of this experiment was to study the biology of this pest in corn and cassava leaves. Caterpillars were collected in area under cultivation with cassava and maintained on artificial diet for two generations. Under controlled conditions in a climatic chamber (B.O.D) in the laboratory (25 degrees, 60 +/- 10% RH and photophase 14 hours) were evaluated daily 50 caterpillars in corn treatments and 50 in cassava, where duration and viability of the larval phase and pupal, weight of pupas were observed after 24 hours, deformation percentage of pupas and adults, longevity, fecundity and total life cycle. The viability of larvae fed on leaves of maize and cassava was 74% and 60%, respectively. The larval period of the insects was shorter in maize 16.89 days (seven instars) and cassava 20.08 days (six instars). The pupal phase lasted 11.42 days in cassava treatment and 10.87 in the maize. The pupal weight of females and males was higher in corn 204.91 mg and 198.97 mg, respectively. The biological cycle varied depending on the ingested food. Adult longevity lasted 9.88 days for insects fed on cassava leaves. Therefore, cassava affected the development of S. frugiperda.
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Pós-graduação em Agronomia (Produção Vegetal) - FCAV
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)