Simultaneous Zinc and selenium biofortification in rice. Accumulation, localization and implications on the overall mineral content of the flour

Zinc (Zn) and selenium (Se) are essential mineral nutrients for humans, but their daily intake is often below adequate levels, particularly in developing countries. To increase these minerals amounts in the edible plant tissues, agronomic biofortification is an efficient strategy. Rice (Oryza sativa L.) is an important food crop, and a crucial source of mineral nutrients. Within the International Rice Research Institute (IRRI) program to guarantee food and nutritional security in Sub-Saharan Africa region, this work aims at evaluating Zn- and Se-biofortification capability of two Mozambican rice cultivars (Makassane and IR-87684-23-2-3-2), considering three Zn levels (0, 300, 600 g ha⁻¹), and three Se levels (0, 150, 300 ha⁻¹). Results showed that foliar Zn and Se application promoted higher accumulation of these minerals in the IR grains. Biofortification was more efficient in the whole grain than in polished grain, with mineral mapping images and quantification showing that Zn, Se, K, Ca, and S accumulation prevailed in the outer part of the grain irrespective of genotype. The 600 Zn and 150 Se g ha⁻¹ dosage maximized Zn content in the flour, while provided Se values that reduced the Se antagonism with Zn, Ca, S and Mo. Still, Se doses can be lowered.