Genetic and genomic drivers of iron and zinc levels in rice grains

Rice (Oryza sativa L.) is the primary staple food for more than half of the world’s population, containing essential human nutrients. Essential micronutrients such as iron (Fe) and zinc (Zn) are very important in human diets, but bioavailability of Fe and Zn is lacking in the rice grains, contributing to global malnutrition and a need for these micronutrients to be biofortified into rice grains. Most of the popular rice varieties only contain 5.0–6.0 mg/kg of Fe and 14.0 mg/kg of Zn, which is not sufficient for rice consumers. This article reviews the phenotypic variation in Fe and Zn concentrations of diverse rice genotypes, association between environmental conditions and accumulation of Fe and Zn in the rice grains, correlation of Fe and Zn concentrations with other agronomic traits, and also genomic analysis of Fe and Zn concentrations in rice. All of these factors are crucial to developing rice varieties with sufficient amounts of Fe and Zn to improve rice grain quality and address mineral deficiency, which can be accomplished through biofortification, conventional rice breeding, and genetic engineering methods.