Resistência do arroz à mancha-parda mediada por silício e manganês

• Autor(a) principal: Zanão Júnior, Luiz Antônio
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5547
• topic: Nutrição mineral; Ácido monosilícico; Doenças de plantas; Mineral nutrition; Monosilicon acid; Plant diseases; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Plant diseases markedly reduce the world food production and their control is more and more being made by using chemical defensives which may cause environmental, economical and social problems. It is needed to search alternatives for controlling the plant diseases lowering the harm caused to the environment. The correct plant nutrition, focusing the more promissing elements for increasing the plant resistance to diseases, as Si and Mn, is one of these alternatives. The aim of this work was, using rice plants cultivated under different doses of Si and Mn, to evaluate: a) the dry matter yield, the angular degree of foliar insertion and the accumulation of macronutrients, cationic micronutrients and Si in the roots, sheaths and leaves, b) the thickness of the leaf abaxial and adaxial epidermis c) the accumulation of soluble phenolic compounds and lignin in the leaves of plants inoculated and non-inoculated with the fungi (Bipolaris oryzae) wich causes the brown spot disesase in rice d) the Si and Mn effects in the rice resistance to the brown spot. Four trials in nutrient solution were carried out in the randomly block design in a fatorial 2 x 3 (0 and 2 mmol L-1 Si; 0.5; 2.5 and 10 µmol L-1 Mn), with 5 replications. The experimental unit was a 4 L plastic recipient with nutrient solution and 2-4 rice plants (Metica-1 cultivar). In the first and second trials no fungi (B. oryzae) inoculation was made and it was determined dry matter yield of roots, sheaths and leaves and the accumulation of macronutrients, cationic micronutrients and Si in roots, sheaths and leaves, at the 45th day after seed germination. Additionally, anatomic studies were done for determination of the thickness of the abaxial and adaxial leaf epidermis. In the third trial, the plants were inoculated with the fungi at the 45th after seed germination and it was determined the length of the incubation time of the disease; lesions per cm2 of leaf area; severity and area underneath the curve of disease progression. In the fourth experiment it were determined the accumulation of total soluble phenolic compounds and lignin in the fungi inoculated and non-inoculated plants. It was made the analysis of variance of the data (F Test, 5% and 1% probability) and the adjustment of regression equations for the responses to Mn, within each Si level. There was a positive and significant effect of the applied Si for all variables related to rice dry matter, to plant architecture, to disease plant resistance, to concentration/accumulation of macronutrients, cationic micronutrients and Si in the plant roots, sheath and leaves, and to the thickness of the adaxial and abaxial epidermis. With the addition of Si, there was increase in the root, sheath and leaf dry matter yield, increase of the thickness of the leaf epidermis and decrease of the angle of foliar insertion witch improved the plant architecture. For the rice resistance to the brown spot disease, the applied Si promoted a prolongment of the disease incubation time of about 9 h, the accumulation of phenolic compounds and lignin in the inoculated leaves, the alleviation of the brown spot severity up to 96%, the decrease of the number of lesion per cm2, and the decrease of the area underneath the disease progress curve. There were significant effects of Mn for most of the characteristics evaluated, however, this was observed only in the treatments with the zero Si dose.