Controle da antracnose do feijão com silício e molibdênio e mecanismos de resistência potencializados pelo silício

• Autor(a) principal: Polanco, Leonora Rodriguez
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1055
• topic: Silício; Resistência induzida; Antracnose; Nutrição; Silicon; Induced resistance; Anthracnose; Nutrition; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Although it is not recognized as an essential nutrient to the plants, Silicon (Si) reduces disease severity in dicotyledons with less capacity of accumulation of this nutrient. The objective of this work was to evaluate the effect of silicon in some components of resistance in bean plants to anthracnose caused by C. lindemuthianum, as well as to quantify physiological and biochemical responses enhanced by this element. Thus, it was evaluated some components of resistance in beans plants (cv. Pérola) grown in nutritive solution with (+Si) or without (-Si) monosilicic acid as well as some biochemical and physiological factors associated with the resistance of bean plants to fungus. Results indicate that supply of Si was efficient in delaying the beginning of the epidemic and reducing the area below anthracnose progress curve (ABAPC) and severity. An increase was found in the activity of phenylalanine ammonia-lyase and e lipoxygenase and in the concentration of metabolites as for example lignin involved in the response to resistance to the host of the pathogens. However no involvement of Si was found in concentrations changes of total soluble phenolic compounds and in the acitivities of enzymes ß-1,3- glucanases, peroxidases and poliphenoloxidase. When the involvement of Si in the reduction of biotic stress caused by anthracnose in the photosynthesis was being analyzed, an increase in rate of carbon net assimiliation (Amax) and in the stomatal conductance (gs) and a decrease in the intercellular CO2 concentration/environment CO2 concentration ratio (Ci/Ca) were found, indicating a lower metabolic inhibition in CO2 in Si-supplied bean plants. Concentrations of chlorophyll a and b and carotenoids increased in the presence of Si, suggesting a more efficient photoreceptor and photoprotection of the photosynthetic system. Root application of Si resulted in the alteration of enzymes involved in the production and catabolism of reactive oxygen species, in which an increase of ascorbate peroxidase (APX), superoxide dismutase (SOD) and glutathione reductase (GR) and a decreased production of hydrogen peroxide (H2O2) were found. Silicon did t the activity of catalase (CAT). The effect of foliar application of potassium silicate (KSi) and ammonium molybdate (NaMo) on anthracnose, grain yield, development and leaf area duration in the bean plant were also studied. Foliar application of KSi decreased AACP and increased grain production by 25% compared with plants without application. It is conjectured the direct effect of this silicate salt on the development of the pathogen and the indirect effect by preventing penetration due to the formation of a physical barrier formed by deposition of the silicate on the leaf. Application of NaMo significantly increased leaf area, which was a consequence of its involvement in nitrogen metabolism. NaMo reduced the intensity of the disease possibly due to its toxic effect as a heavy metal on the fungus. The effects of KSi and NaMo reported in this study suggest that its incorporation into an integrated management system with positive effects on the reduction of the epidemic, the increase in grain production and on the environment.