Aplicação de selênio em trigo: potencial de biofortificação agronômica e mitigação de restrição hídrica

Abstract

Selenium (Se) is an essential element for humans and animals, which require a very low amount of the element for adequate nutrition (intake of 70 μg day-1 for an adult human). However, malnutrition, including the deficiency of this element, has brought public health problems in poor regions around the world, in order to solve this problem agronomic biofortification has aroused interest, as this practice provides the plants with elements that will be incorporated into organic compounds and ingested by humans, increasing food security and reducing malnutrition. Due to the increased activity of enzymes in the antioxidant system of plants, Se has been used to reduce the deleterious effects caused by environmental stresses, especially water stress, a problem that limits agricultural production. Thus, this study aimed to evaluate both the effect of Se application via soil on the efficiency of Se accumulation by wheat, as well as on the resistance of the crop to water stress imposed in the phenological phase of flowering and grain filling. The experiment was carried out in a greenhouse at the Federal University of Lavras - MG, in the form of an experimental design in randomized blocks, in a 5x3 factorial scheme, with four replications. The first factor refers to the different doses of Se (0; 0.25; 0.50; 1.0 and 2.0 mg dm-3) in the form of sodium selenate (Na2SeO4) and the second factor refers to the phenological phase of the crop in which water stress was applied. Thus, water stress was induced in the phenological phase of flowering, grain filling and a control treatment in which there was no water restriction. The application of Se via soil, in the form of Na2SeO4, increases the concentration of this element in wheat grains. This effect also happens for the concentrations of sulfur and nitrogen in the shoot. However, the dose of 0.25 mg dm-3 of Se associated with water stress in the flowering phase increases tillering, promotes gains in biomass, grain mass and productivity, in addition to increasing nitrogen (N) metabolism. Decreases oxidative stress due to higher superoxide dismutase (SOD) activity and lower concentration of hydrogen peroxide (H2O2). On the other hand, the dose of 1.0 mg dm-3 of Se promotes greater plant protection when stress is induced in the grain filling phase. Since Se preserved the photosynthetic apparatus of plants increasing the chlorophyll a and b indexes, photosynthetic rate, stomatal conductance and water use efficiency. In addition, it increased defenses against oxidative stress due to increased SOD and catalase activity, decreasing H2O2 concentrations and lipid peroxidation (MDA). In addition, it confers an increase in grain mass and production of grains rich in sulfur, manganese and zinc. These results reinforce the positive role of Se by reducing the harmful effects caused to plants under severe water restriction. Furthermore, it characterizes wheat as a species suitable for agronomic biofortification programs.