Comportamento da ferrugem do cafeeiro pela aplicação de silício

• Autor(a) principal: Missio, Vivian Carré
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1033
• topic: Café; Silício; Microscopia eletrônica; Nutrição; Enzimas; Ferrugem do cafeeiro; Coffee; Silicon; Electron microscopy; Nutrition; Enzymes; Coffee rust; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Silicon (Si) plays an important role in plant-environment interaction, mainly because it helps plants to better performance under many abiotic or biotic types of stress. Therefore, this study aimed to investigate the possibility of using Si to control coffee leaf rust, caused by the fungus Hemileia vastatrix, on coffee. Indeed, it was also elucidated some possible mechanisms of resistance, at microscopic and biochemical levels, potentiated by this element. In the first experiment, the effect of potassium silicate (KSi) rates (8, 20, 40, and 60 g L-1) without (pH 10.5) or with (pH 5.5 and 7.5) pH changes on uredospores germination was evaluated. In the second experiment, the effect of foliar spray of KSi, at the same rates and pH values mentioned above, on coffee plants (cv. Catuaí vermelho 44 ) to control rust was tested. In the third experiment, the protector effect of KSi rates (15 and 35 g L-1; pH 5.5) on coffee leaves against fungus infection was studied. In the fourth experiment, the uptake, translocation, and Si deposition on coffee leaves were determined by grown plants on modified Clarck s nutrient solution containing 0 or 2 mmol of Si L-1. In the fifty experiment, some events occurring during the pathogenesis of H. vastatrix on coffee leaves were investigated by using the scanning electron microscopy (SEM). Some components of host resistance, agronomic variables (dry matter, shoot height, root length, and stem diameter), as well as the activity of the enzymes quitinase (QUI), glucanases (GLU), and peroxidases (POX) were evaluated. Si content in leaf and root tissues was also quantified. KSi inhibited uredospores germination. The foliar application of KSi was efficient to decrease rust severity; however Si did not any effect in reducing disease when supplied from nutrient solution. KSi showed protector effect on rust control until 25 days after spray. It was not observed an increase on Si content in leaf tissue of plants sprayed with KSi or grown in nutrient solution amended with 2 mmol Si L-1. SEM observations showed that on coffee leaves from plants sprayed with KSi, a fewer number of pustules on leaves associated with a great extension of leaf area covered by plates of polymerized KSi were observed. There was no difference for the components of host resistance and the agronomic variables evaluated between the treatments 0 and 2 mmol Si L-1. The activity of the enzymes QUI, GLU, and POX did not show any increase on inoculated plants regardless of the presence of Si. It can be concluded from this study that coffee plants were inefficient in uptake Si from either roots or leaves in order to decrease rust severity; however, the spray of KSi showed potential to decrease rust through a mechanism other than one possibly mediated by Si actively uptaked by roots.