Seedling Priming with Selenium Enhances the Biofortification Strategies in the Production of Broccoli Florets

Agronomic biofortification strategies have been used to increase selenium (Se) concentrations in edible parts, with broccoli cultivation showing high potential. Recent studies have demonstrated that prior application of selected elements during the seedling phase (priming) can enhance agronomic biofortification when this element is applied during the adult phase; however, no such effect has yet been reported for Se. Additionally, Se concentration in broccoli florets may be affected by post-harvest processing, thus determining losses is essential in the agronomic biofortification process. This study aimed to determine whether seedling production with priming using selenium (Se) could enhance different agronomic biofortification strategies for Se, and to evaluate the effect of post-processing on the Se concentration in broccoli. Seedlings were produced with and without priming (75 mg L−1 of Se), and different application methods (soil and foliar), sources, and doses of Se were tested on Se concentration in broccoli florets. Foliar application strategies for Se were more effective than soil application for producing Se-biofortified broccoli. Seedlings produced and subjected to Se application to promote the priming effect enhanced Se absorption and increased Se concentration in broccoli florets. However, the highest Se absorption with a dry mass concentration exceeding 18 mg kg−1 reduced broccoli production, except for Se applied via multi-nutrient fertilizer. Foliar fertilization strategies using 50 g of Se ha−1 via multi-nutrient fertilizer, Se + organic compounds, and sodium selenate, along with the use of seedlings produced with priming and the application of 50 g of Se ha−1 via multi-nutrient fertilizer using seedlings produced without priming, can provide Se amounts reaching the human dietary requirement of 60–70 µg day−1, based on the adequate daily consumption of broccoli (40 g of broccoli). Different processing stages do not cause significant losses of Se in biofortified florets. Therefore, it is concluded that seedlings produced with priming combined with foliar Se applications are effective strategies for promoting agronomic biofortification of Se in broccoli florets for the human diet.