Resistência induzida na interação trigo - Pyricularia oryzae e elaboração de uma escala diagramática para estimar a severidade da brusone

• Ano de defesa: 2012
• Autor(a) principal: Rios, Jonas Alberto
• Orientador(a): Rodrigues, Fabrício de ávila
• Banca de defesa: Cunha, Luis Claudio Vieira da , Resende, Renata Sousa
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• 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: Indutores; Biotrofia; Mancha foliar; Trigo; Brusone
• Palavras-chave em Inglês: Inducers; Biotrofia; Leaf spot; Wheat; Blast
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/4403

The blast, caused by the fungus Pyricularia oryzae (Cooke) Sacc., Is a major disease affecting wheat (Triticum aestivum L.). This study aimed to investigate the effect of acibenzolar-S-methyl (ASM), jasmonic acid (JA) and ethylene (ET) in resistance of wheat in response to infection by Pyricularia oryzae, as well as develop and validate a diagrammatic scale to quantify the severity of wheat blast. In the first study, two experiments were conducted in a greenhouse in a completely randomized design with four treatments and four replications. Wheat plants of BRS-229 and BR-18 were grown in plastic pots with a capacity of 1 dm3 of substrate. The treatments were: T1- distilled water (control), T2 - 0.1 mM jasmonic acid (JA), T3 - 300 mg / L acibenzolar-S-methyl (ASM) and T4 - 0.5 mM ethylene (ET) (Ethephon). We evaluated the components of resistance: incubation period (IP), number of lesions (NL) per cm2 of leaf area, lesion size (TL) in mm and severity. The severity values were used to calculate area under the curve of the progress of blast (AACPB). To evaluate the effect of inducers on the biochemical mechanisms of resistance was determined the activity of peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), chitinase (CHI), β-1 ,3-glucanase (GLU) and lipoxygenase (LOX), and the concentration of malondialdehyde (MDA). For BRS- 229, the AACPB was significantly reduced in 57, 35 and 61%, respectively, with the application of AJ, ASM and ET in relation to the control (distilled water). Significant reduction of 53, 35 and 59% in AACPB with the application of AJ, and ET in ASM plants of cultivar BR 18 in relation to the control treatment. The application of AJ, ASM and ET was reduced by 69, 38 and 68% respectively for the NL BRS-229 and 63, 41 and 66% for BR-18. The NL and AACPB were significantly higher with the application of ASM in relation to the application of AJ and ET for the two cultivars. There was no significant difference between treatments for the PI and TL in both cultivars plants sprayed with inducers showed higher activities of POX, PPO, CHI, GLU and LOX relative to control. It was concluded that the application of the inductors AJ, ASM and ET increased enzyme activities in wheat during the infectious process of P. oryzae thus reducing the severity of the blast. In the second study, a diagrammatic scale with ten levels of severity, namely 0.1, 1, 2, 4, 8, 16, 24, 32, 52, 72%. To validate the scale, 10 inexperienced appraisers estimated the severity of the blast. The accuracy and precision of the evaluators were analyzed by correlation coefficient concordant Lin's (ρc) and simple linear regression between actual and estimated severity severity with and without the use of the scale. The scale provided satisfactory accuracy and precision (average R2 of 94.5%) with absolute errors of around 15%. The values of u, υ and ρc were improved in 90, 100 and 90% of the evaluators respectively, using the scale. The reproducibility among raters using the scale was high (R2 greater than 90 for 64.4% of cases). The scale obtained is adequate to estimate the severity of the blast and wheat can be used in studies where it is necessary to quantify this disease.