Iron and Selenium Biofortification of Crops: Concepts, Soil Constraints, Strategies, and Perspectives

Iron (Fe) and selenium (Se) deficiencies are global health concerns associated with adverse health outcomes. Plants constitute a dietary source of these elements, particularly for individuals following plant-based diets. However, plant Fe availability is limited by soil processes that reduce Fe mobility and uptake, whereas Se accumulation is constrained by the low abundance of Se in soils. Increasing Fe and Se concentrations in edible plant parts through biofortification represents a sustainable strategy to alleviate micronutrient deficiency. This review examines the mechanisms governing Fe and Se uptake, translocation, metabolism, and genetic regulation, and discusses current biofortification strategies, including agronomic practices, natural and microbial-based approaches, conventional breeding and marker-assisted selection, transgenic technologies, and nanoparticles. While cereals remain the principal targets of large-scale biofortification programs, recent advances in horticultural crops are also highlighted because of their growing nutritional and commercial importance. Current evidence indicates that integrated agronomic and genetic approaches are more effective than single interventions, although simultaneous Fe and Se biofortification remains largely underexplored. Successful biofortification is also strongly influenced by soil properties, nutrient interactions, and crop genotype. Emerging tools, including plant–microbe interactions and synthetic biology, offer promising opportunities to enhance micronutrient accumulation and bioavailability. Further research should optimize integrated Fe–Se biofortification strategies while addressing agronomic and socioeconomic constraints to support their large-scale adoption and contribute to sustainable food systems.