Integrating genetic and agronomic fortification improves zinc, iron, and protein concentrations in rice grain: A meta-analysis

Rice, consumed by half of the world's population, is inherently low in zinc (Zn), iron (Fe), and protein. We compiled data from 245 studies across 34 countries to evaluate the impact of genetic, agronomic, and processing interventions on rice grain Zn, Fe, and protein concentrations. Zn-biofortified cultivars had 9.8% higher grain Zn concentrations than non-biofortified cultivars, while Fe-biofortified cultivars did not exhibit a significant improvement in Fe content. In the absence of Zn and Fe fertilization, the probability of achieving the breeding target concentrations of Zn (28 mg kg-1) and Fe (15 mg kg-1) was only 4.0% and 10.5%, respectively in white (polished) rice. On the other hand, Zn and Fe fertilization increased the probability of achieving the same targets in white rice by 41.3% and 67.7% for Zn and Fe, respectively. Milling and polishing of brown rice grains reduced Zn, Fe, and protein concentrations by 21%, 70%, and 6.5%, respectively. Our findings emphasize the need for the combined use of genetic and agronomic fortification and the consumption of parboiled rice to attain desired health impacts.