Respostas fisiológicas de cultivares de feijão sob déficit hídrico e inoculação de Macrophomina phaseolina

Abstract

The bean crop has great economic importance for Brazilian agribusiness, however unfavorable environmental factors and the occurrence of diseases can affect its yield, among which can be mentioned the water deficit and the incidence of fungal diseases. Bean plants under water deficiency show physiological and morphological changes, in addition, the lack of water can facilitate the infection of pathogens, either by weakening the plant, as well as by favoring the multiplication and development of pathogens. This is the case of Macrophomina phaseolina, causal agent of charcoal rot, a disease that harms the root system of plants, promoting lesions that impede their growth and development. The aim of this study was to evaluate and characterize morphophysiological, protective and growth variables in three bean cultivars developed by Embrapa BRS Guariba, Tumucumaque and Esteio. For this purpose two experiments were conducted in a greenhouse, where the plants were submitted to M. phaseolina inoculation during the sowing, with suspension of irrigation 27 days after sowing. The first one was carried out with four treatments Control, Water Deficit, Inoculation and Inoculation with Water Deficit, and gas exchange, chlorophyll fluorescence, relative water content in leaves (RWC%) and chlorophyll spad index were evaluated. The Guariba cultivar showed greater tolerance to the water deficit condition, but greater sensitivity under inoculation, which did not prevent its recovery. The cultivar Tumucumaque showed intermediate tolerance to the parameters evaluated, while Esteio was more sensitive to water deficit and pathogen inoculation, since it did not show recovery for gas exchange. The second experiment aimed to evaluate growth and protective responses of the same cultivars and experimental conditions. During the evaluation period, Guariba and Tumucumaque cultivars presented better results, and even when they were smaller, they later recovered, while the Esteio cultivar was more affected by water deficit associated with inoculation of the pathogen. In view of the results of this study, it can be concluded that the water deficit alone and/or associated with the pathogen triggered negative responses, both for gas exchange and growth, however, BRS Guariba and Tumucumaque cultivars showed better results in stressful conditions, in contrast to BRS Esteio that demonstrated greater sensitivity.