Silício no manejo da antracnose do sorgo: componentes de resistência e respostas bioquímicas de defesa

• Ano de defesa: 2007
• Autor(a) principal: Resende, Renata Sousa
• Orientador(a): Rodrigues, Fabrício de ávila
• Banca de defesa: Carvalho, Murilo Geraldo de , Grossi, José Antônio Saraiva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso embargado
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Sorgo - Resistência a Colletotrichum sublineolum; Antracnose; Sorgo - Efeito do silício; Sorgo - Metabolismo; Sorghum bicolor
• Palavras-chave em Inglês: Sorghum - Resistance to Colletotrichum sublineolum; Anthracnose; Sorghum - Effect of silicon; Sorghum - Metabolism; Sorghum bicolor
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::MELHORAMENTO VEGETAL
• Link de acesso: http://locus.ufv.br/handle/123456789/4434

This work aimed to study the effect of silicon (Si) on some components of resistance to anthracnose, caused by the fungus Colletotrichum sublineolum, in lines of sorghum susceptible ( BR009 ) and resistant ( BR005 ) to this pathogen. Indeed, some biochemical responses of host defense, possibly potencialized by Si, were quantified. The first experiment, carried out under greenhouse conditions, was arranged in a randomized design with three replications and repeated twice. Plants of two sorghum lines were amended with five Si rates: 0, 0.06, 0.12, 0.24 and 0.30 g/kg of soil using wollastonite as a source of Si. Calcium (Ca) carbonate was added to pots that received 0, 0.06, 0.12 and 0.24 g Si kg of soil to equilibrate the amount of Ca present in these treatments with the treatment containing 0.30 g Si/kg of soil. Plants were inoculated at 30 days after emergence. The following components of resistance were evaluated: incubation period (IP), latent period (LP60), relative infection efficiency (RIE), area under anthracnose index curve (AUAIC), final severity (FS) and real severity (RS) for both percentagem of necrotic leaf area (NLA) and pigmented leaf area (PLA) estimated by using the software QUANT. Data for each variable at each experiment were pooled before analysis. A quadratic regression model best described the effect of Si rates on PI, LP60, RIE, AUAIPC, FS and real severity for both NLA and PLA on the susceptible line. The lowest values for RIE, AUAIPC, FS, RS for NLA and RS for PLA occurred at 0.25 g Si/kg of soil. It was not detected the presence of acervula on leaves of the resistant sorghum line, therefore the LP60 and RIE were not evaluated. There was no significative effect of Si rates on PI, AUAIC, FS and RS for both NLA and PLA on the resistant line. The Si content in sorghum tissue was directly related to the amount of Si applied to the soil and increased relative to the control by 55 and 58%, respectively, in the susceptible and resistant lines. There was no significant change in Ca content in the sorghum tissue for any of the lines tested as well as among the combinations between wollastonite and calcium carbonate. In the second experiment, the content of anthocianins (CA), total soluble phenolics (TSP) and lignin-thioglycolic derivatives (LTAD) were quantified. This 2x2x2 factorial experiment was carried out in a randomized design with three replications. The factors studied were two Si rates (0 and 0.3 g/kg of soil), two sorghum lines ( BR009 and BR005 ) and inoculated or non-inoculated plants. On inoculated plants amended with Si, the CA was higher than on inoculated plants non-amended with Si. The content of TSP was higher on inoculated plants from the resistant line amended with Si than on plants from the same line non-amended with Si. The content of LTAD was significantly higher on inoculated plants from the susceptible line non-amended with Si than on plants from the resistant line. The content of TSP and LTAD did not explain the resistance level for both sorghum lines to the pathogen, independently of the presence of Si. The content of CA was greater in plants amended with Si and explained their increased level of resistance to anthracnose.