Efeito de variáveis climáticas sobre a severidade da mancha angular do feijoeiro comum e detecção de resistência de Pseudocercospora griseola (Sacc.) Crous & Braun ao fungicida carbendazim

• Autor(a) principal: Yoshida, Fernanda
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/0013000003mgx
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/6919
• topic: Phaseolus vulgaris; precipitação; El Niño; Alamar Blue; Produtividade; Phaseolus vulgaris; Monthly rainfall; El Niño; Alamar Blue; Crop yield; AGRONOMIA::FITOSSANIDADE

The influence of climatic variables on angular leaf spot of common bean (Phaseolus vulgaris L.) and the reaction of the causal agent Pseudocercospora griseola (Sacc.) Crous & Braun to the carbendazim fungicide were assessed in this study. A methodology for assessing the pathogen resistance to the carbendazim fungicide, of wide use in Brazilian agriculture, was developed at Embrapa Rice and Beans, in Santo Antônio de Goiás. The test was based on P. griseola conidia suspensions at concentrations of 103, 104 and 105 spores mL-1, fungicide concentrations of the at 1 ppm, 10 ppm and 100 ppm per mL-1at the presence of Alamar Blue dye. Alamar Blue is an indicator of cell activity, where the metabolism of viable cells corresponds to a higher dye reduction and a colorimetric reaction. The experimental results were assessed with the support a spectrophotometer to quantify the amount of reduced dye, and thus, to verify the pathogen’s resistance to the fungicide. The results demonstrated the feasibility of the method and greater resistance of the isolate Pg 669 to carbendazim in comparison to isolates Pg 410 and Pg 786. Furthermore, the recommended methodology consisted on fungicide at 100 ppm, 1 × 104 conidia mL-1and 40 hours of incubation at 25ºC. Another study considered the relationships between angular leaf spot severity, crop yield and climate variables to estimate the impacts of monthly rainfall and the El Niño Southern Oscillation (ENSO) phenomenon on the disease and yield losses in crops established in the spring/summer (November-February) or fall (February-May) season, in crops established in the spring/summer (November-February) or fall (February-May) season, in different Brazilian municipalities, between 2001 and 2010. The disease data was retrieved from experiments of value, cultivation and use (VCU), conducted by Embrapa and its partners, with the cultivars Pérola, BRS Grafite e BRS Requinte. These tests were carried out in a randomized block design with three replications. The results showed differences (p<0.05) between cultivars and between planting seasons. By means of regression analysis, an inversely proportional relationship between yield and disease severity was found. The principal components analysis, in turn, revealed that ENSO influences differently disease severity and crop yield according to the location of the experiments in the Brazilian states of Goiás, Paraná and Pernambuco. These results provide new evidences about the efficiency of commercially used fungicides for angular leaf spot management, demonstrate the impacts of the disease on a regional scale, and support predictive models of disease and risk assessments of climate change on the development of crops.