Análises fisiológicas e bioquímicas da resistência do algodão à mancha de ramulária mediada pelo silício

• Autor(a) principal: Curvêlo, Carmen Rosa da Silva
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1213
• topic: Algodão; Enzimologia; Fotossíntese; Mancha de ramulária; Cotton; Enzymology; Photosynthesis; Areolate mildew; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

The occurrence of diseases is a major problem that affects most of the cropland in Brazil, especially those located in the Midwest of region. Although silicon (Si) is not considered an essential element in plants, this nutrient has been shown to reduce the severity of many diseases in many plant species when accumulated in the shoot there by increasing plant resistance against pathogen attack. Respite this beneficial effect is widely reported in the literature, little is known about the Physiological and Biochemical mechanisms regulates by this element in the cotton-Ramularia areola pathosystem. Thus, the objective of this study was to evaluate the effect of Si in reducing Areolate mildew symptoms, as well as investigate the physiological and biochemical aspects of resistance mediated by this element. Cotton plants of the cultivars NuOpal (susceptible) and BRS Buriti (moderately resistant) were grown in pots with nutrient solution containing silicon (+Si) or not (-Si). The Si application reduced the area under the Areolate mildew progress curve (AUPCAM) in cotton plants. The increase in the concentration of phenolic compounds and derivatives of lignin-thioglycolic acid in plants of the two cultivars supplied with Si, and the increased activity of defense enzymes peroxidase (POX), polyphenol-oxidase (PPO), chitinase (CHI), ß-1, 3-glicanase (GLI) and phenylalanine ammonia-lyase (FAL) in plants of the cultivar NuOpal, potentiated the chemical defensive mechanisms against pathogen infection, as reported in the literature, but the PPO and FAL enzyme activity in BRS Buriti plants were not enhanced by Si. The provision of Si to the cotton plants of the two cultivars resulted in higher concentrations of H2O2 by reducing the activity of CAT, while increases in the activity of the enzymes APX, SOD and GR may have contributed to reduce the concentrations of MDA and EE for both cultivars. There were significant increases in LOX activity in plants supplied with Si of both cultivars. The supply of Si cotton plants of two cultivars increased the net rate of fixation of CO2 (A) in parallel with increases in stomatal conductance (gs). The concentrations of chlorophyll a (cla), chlorophyll b (clb) were higher in plants supplied with Si at later stages of infection to grow NuOpal but carotenoids were those who suffered less alteration.