International Journal of Plant & Soil Science

Iron toxicity is an important abiotic constraint to rice production, particularly in flooded and acid sulphate soils where high concentrations of soluble ferrous iron can accumulate. This review synthesises current knowledge of iron acquisition, toxicity symptoms, tolerance mechanisms, and opportunities for the genetic improvement of rice under iron-toxic conditions. Rice possesses a distinctive iron-acquisition system that combines phytosiderophore-mediated uptake with the direct absorption of ferrous iron. Although this system supports iron nutrition under flooded conditions, excessive iron uptake can promote reactive oxygen species formation and cause leaf bronzing, impaired growth, nutrient imbalance, reduced photosynthetic performance, and yield loss. Rice plants respond through multiple anatomical, physiological, biochemical, and molecular defence mechanisms. These include rhizospheric iron oxidation and plaque formation, restriction of iron movement from roots to shoots, tissue compartmentalisation, ferritin-mediated sequestration, chelation, and enzymatic and non-enzymatic antioxidant responses. Iron transporters, regulatory proteins, chelators, and stress-responsive genes contribute to maintaining cellular iron homeostasis and reducing oxidative injury. Considerable genotypic variation in tolerance provides opportunities for breeding through conventional selection, marker-assisted approaches, quantitative trait locus analysis, genome-wide association studies, and other genomic tools. Integrating physiological screening with molecular and genetic approaches can improve understanding of the complex basis of iron-toxicity tolerance and support the development of rice varieties better adapted to iron-toxic environments.