Selenium Biofortification in Rice Under Water Deficit: Plant Physiology and Post-Cooking Mineral Bioaccessibility

Abstract

Since selenium (Se) is an essential element for humans and beneficial for mitigating abiotic stresses in plants, and considering that rice is a global staple food that may lose nutrients during cooking, this study evaluated the effects of soil-applied Se on rice plants subjected to water deficit and its impact on the bioaccessibility of Se and other minerals in flour and cooked grains. The experiment followed a 5 × 2 factorial design with five Se doses (0, 0.2, 0.4, 0.6, and 1.0 mg kg -1 ) and two water regimes (irrigated and water-deficient). Physiological parameters, biomass, and yield were assessed, and a simulated human gastrointestinal system was used to determine the bioaccessibility of Se, Fe, Mn, and Zn. Selenium application and water management did not affect biomass or grain yield, but Se provided a practical advantage by maintaining physiological resilience and yield stability under water deficit. Se reduced malondialdehyde (MDA) concentrations, increased water-use efficiency (WUE) by approximately 35.30% under water deficit, and enhanced antioxidant enzyme activity, while water deficit decreased CO₂ assimilation. To achieve optimal grain Se levels while mitigating MDA and enhancing WUE under water deficit, 0.6 mg kg -1 was the ideal rate. Se bioaccessibility did not differ between flour and cooked grains, whereas cooking significantly reduced the bioaccessibility of iron (Fe), manganese (Mn), and zinc (Zn) by approximately 41%, 69%, and 81%, respectively. Soil Se application is an effective strategy for biofortifying rice grains and mitigating water stress. Maintaining Se bioaccessibility post-cooking highlights the potential of biofortification to reduce hidden hunger and promote food security.