Biofortified indica rice attains iron and zinc nutrition dietary targets in the field

Abstract

More than two billion people are micronutrient deficient. Polished grains of popular rice varieties have concentration of approximately 2 μg g-1 iron (Fe) and 16 μg g-1 zinc (Zn). The HarvestPlus breeding programs for biofortified rice target 13 μg g-1 Fe and 28 μg g-1 Zn to reach approximately 30% of the estimated average requirement (EAR). Reports on engineering Fe content in rice have shown an increase up to 18 μg g-1 in glasshouse settings; in contrast, under field conditions, 4 μg g-1 was the highest reported concentration. Here, we report on selected transgenic events, field evaluated in two countries, showing 15 μg g-1 Fe and 45.7 μg g-1 Zn in polished grain. Rigorous selection was applied to 1,689 IR64 transgenic events for insert cleanliness and, trait and agronomic performances. Event NASFer-274 containing rice nicotianamine synthase (OsNAS2) and soybean ferritin (SferH-1) genes showed a single locus insertion without a yield penalty or altered grain quality. Endosperm Fe and Zn enrichment was visualized by X-ray fluorescence imaging. The Caco-2 cell assay indicated that Fe is bioavailable. No harmful heavy metals were detected in the grain. The trait remained stable in different genotype backgrounds.