Plant–Microbe Interactions as Emerging Biomanufacturing Platforms for Iron Biofortification, with Rice as a Principal Model

Iron deficiency remains a major public health challenge in populations relying on staple foods with low iron bioavailability, including polished rice. This narrative review evaluates how beneficial plant-associated microorganisms may support iron (Fe) biofortification by influencing Fe mobilization in the rhizosphere, root acquisition, and subsequent transport to edible tissues. We organize the existing evidence along a soil–plant–grain–food continuum and distinguish measured outcomes from proposed mechanistic links. This evidence-based framework is described as a plant–microbe biomanufacturing platform in a strictly conceptual sense: neither plants nor microorganisms manufacture Fe; rather, their interactions can modify its mobilization and distribution. Most studies have demonstrated microbial effects on Fe availability and plant physiology, but fewer have established increased Fe in grain, and evidence for Fe being retained after polishing or absorbed by consumers remains scarce. Future work should integrate field validation, nitrogen and water management, Fe localization, food processing, and nutritional bioavailability. This approach may help prioritize testable interventions without equating microbial activity or higher total grain Fe with improved human iron status.