Observações microscópicas do efeito do silício no controle da cercosporiose em três variedades de cafeeiro
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2005
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Resumo
A cercosporiose do cafeeiro é uma das mais importantes doenças na fase de viveiro. Os objetivos desse trabalho foram avaliar o efeito da aplicação de Si (1g de CaSiO3 incorporado em 1kg do substrato utilizado para encher os tubetes) no controle dessa doença em três variedades de cafeeiro (Catuaí, Mundo Novo e Icatu) e determinar quais os possíveis fatores de resistência associados. As plantas com dois pares de folhas foram inoculadas com suspensão de 1,4 x 10 4 conídios de Cercospora coffeicola por ml. Aos sete meses após o transplantio, avaliou-se a porcentagem de folhas lesionadas e o número total de lesões por planta. Após essa avaliação, retiraram-se amostras das folhas para o estudo em microscopia eletrônica de varredura (MEV) e microanálise de raios X (MAX). As plantas da variedade Catuaí tratadas com silicato tiveram redução de 63,2% nas folhas lesionadas (%) e de 43% no total de lesões por planta, em relação à testemunha. A MAX e o mapeamento para Si indicaram distribuição uniforme do elemento em toda a superfície abaxial das folhas de cafeeiro nas três variedades tratadas. Nas folhas das plantas não tratadas, o Si foi raramente encontrado. Nas imagens de MEV também foi observada camada de cera bem desenvolvida na superfície inferior das folhas originárias de todas as plantas tratadas, sendo esta mais espessa em Catuaí e rara ou ausente nas não tratadas.
Brown eye spot of coffee is an important nursery disease. The goal of this work was to evaluate the effect of silicon (1g of CaSiO3 incorporated in 1kg of substrate used to filling the containers) on the control of this disease in three coffee cultivars (Catuaí, Mundo Novo and Icatu) and determine which resistance factors were stimulated. Young plants with two pairs of leaves were inoculated with a suspension containing 1.4 x 10 4 Cercospora coffeicola conidia.ml-1. Seven months after inoculation the plants were evaluated to determine the percent of leaves with disease (%) and the total number of lesions per plant. Before the evaluation, leaf samples were studied using a scanning electron microscope and X-ray microanalysis. In the plants of the Catuaí cultivar treated with silicon, there were observed reduction of 63,2% on the leaves with lesions (%) and of 43% on the total lesions per plant, in relationship the not treated plants. X-ray microanalysis and mapping of Si showed uniform distribution of element in the all abaxial surface of leaves of all cultivars treated. On the leaves of not treated plants, the Si was rare or absent. Scanning electron microscopy also showed a very well developed wax layer on the lower leaf surfaces of all cultivars, but this layer was thicker in the Catuaí cultivar and thin or absent in control plants.
Brown eye spot of coffee is an important nursery disease. The goal of this work was to evaluate the effect of silicon (1g of CaSiO3 incorporated in 1kg of substrate used to filling the containers) on the control of this disease in three coffee cultivars (Catuaí, Mundo Novo and Icatu) and determine which resistance factors were stimulated. Young plants with two pairs of leaves were inoculated with a suspension containing 1.4 x 10 4 Cercospora coffeicola conidia.ml-1. Seven months after inoculation the plants were evaluated to determine the percent of leaves with disease (%) and the total number of lesions per plant. Before the evaluation, leaf samples were studied using a scanning electron microscope and X-ray microanalysis. In the plants of the Catuaí cultivar treated with silicon, there were observed reduction of 63,2% on the leaves with lesions (%) and of 43% on the total lesions per plant, in relationship the not treated plants. X-ray microanalysis and mapping of Si showed uniform distribution of element in the all abaxial surface of leaves of all cultivars treated. On the leaves of not treated plants, the Si was rare or absent. Scanning electron microscopy also showed a very well developed wax layer on the lower leaf surfaces of all cultivars, but this layer was thicker in the Catuaí cultivar and thin or absent in control plants.
Descrição
Trabalho apresentado no Simpósio de Pesquisa dos Cafés do Brasil (4. : 2005 : Londrina, PR). Anais. Brasília, D.F. : Embrapa Café, 2005.
Palavras-chave
Café Mancha de olho pardo Coffea arabica Cercospora coffeicola, Coffee Brown eye spot Coffea arabica Cercospora coffeicola
Citação
Pozza, Adélia A. A.; Pozza, Edson A.; Alves, Eduardo; Carvalho, Janice G. de; Guimarães, Paulo T. G. Observações microscópicas do efeito do silício no controle da cercosporiose em três variedades de cafeeiro. In: Simpósio de Pesquisa dos Cafés do Brasil (4. : Londrina, PR : 2005). Anais. Brasília, D.F. : Embrapa - Café, 2005. (1 CD-ROM), 6p.