Zinc biofortification in food-type soybean cultivars

Abstract

Reducing risks of zinc deficiency by diversifying diet and agricultural interventions represents a challenge for the future. To verify zinc biofortification in food-type soybean cultivars, we carried out three studies. In the first one, we assessed the effects of fertilization with zinc on the biofortification of food-type soybean cultivars using the fully randomized design with a 5x3 factorial arrangement and four repetitions. We tested five strategies of fertilization with zinc (control without zinc, soil fertilization, fertilization of leaves at vegetative stage 4, leaves at vegetative stage 8, leaves at reproductive stage 4) on three soybean cultivars (BRS 213, BRSMG 790A and BRS Favorita RR®). The second study aimed at verifying the effect of doses of zinc applied on the leaves of food-type soybean cultivars in order to fortify the grains. We used the fully randomized design with four repetitions and a 5x5 factorial arrangement: five soybean cultivars (BRS 010, BRS 213, BRSMG 790A, BRSMG 800A and Favorita RR®) combined with five doses of zinc applied to leaves at reproductive stage 4 (0, 0.91, 1.81, 2.73 and 6.37 mg L-1). In the third study, we evaluated the effect of zinc and iron levels on soybean plants (cultivar BRS 290A), cultivated in a hydroponic system divided into two experiments. We used a 4x3 factorial arrangement in the first one: four levels of zinc (2, 10, 20 and 40 μM) and three levels of iron (1, 7.7, and 77 μmol L-1) with four repetitions. In the experiment on absorption, the plants were cultivated in a modified solution with three levels of iron (1, 7.7 and 77.7 μmol L-1) combined with a high concentration of zinc (40 μM). The plants were harvested at different periods to study absorption (1, 2, 4, 6, 10, 16, 22, 24, 32 and 48 hours). The fertilization with zinc through leaves at stage 4 of reproductive development promotes greater biofortification of soybean grains, when the soil lacks this nutrient. Cultivar BRSMG 790A was the best and most effective at accumulating zinc and implementing it to the grains. Increasing the doses of zinc applied to the leaves promotes fast responses to the content of this nutrient in soybean grains. Different levels of Zn and Fe combined affect the absorption and the mineral state, as well as the growth of soybean plants, thus creating different phenotypes.