Foliar Selenium Application Modulates Grain Yield, Antioxidant Responses, and Mineral Bioaccessibility in Rice Under Water Deficit

Water deficit at flowering is a major constraint to rice production. Foliar selenium (Se) application is an agronomic biofortification strategy that can enhance plant tolerance to abiotic stress while enriching grains with Se, yet its nutritional benefit depends on how much Se remains bioaccessible after cooking. This study evaluated the effects of foliar Se application (0, 1, 2, 3, and 5 mg pot−1) on rice under two irrigation regimes (well-watered and water deficit imposed during flowering). Water deficit did not reduce grain yield at any Se rate, and at 2 mg pot−1, grain yield under water deficit was ~11% higher than under well-watered conditions. Foliar Se application altered SOD, POD, and APX activities, whereas CAT was affected only by the irrigation regime, and MDA concentrations were reduced at Se rates of 2 and 5 mg pot−1. Selenium concentrations in leaves and grains increased with foliar application rates. Selenium application also influenced the concentrations of K, P, Ca, Mg, S, Cu, Fe, Mn, and Zn in grains. However, in vitro digestion revealed that cooked intact brown rice grains showed lower elemental bioaccessibility than uncooked rice flour (e.g., Se bioaccessibility decreased from 68.47% in flour to 45.82% in cooked grains, and S decreased by up to 99%), reflecting the combined effects of cooking and grain matrix integrity. Foliar Se application effectively enriched rice grains with Se and reduced lipid peroxidation, but post-cooking evaluations are essential to determine actual mineral bioaccessibility.