Grain zinc, iron and protein concentrations of contemporary wheat cultivars fall short of targets for human health

Grain zinc (Zn), iron (Fe) and protein concentrations have declined in wheat cultivars released since the 1960s. Here we conducted a meta-analysis of field studies to provide a global synthesis of how genetic, environmental and agronomic factors influence grain Zn, Fe and protein concentrations. The probability of achieving the Zn target (38 mg kg^-1) was 38.9% across bread wheat and 42.7% of durum wheat grain samples, but only 28.5% of released bread wheat cultivars met this target. The probability of achieving the Zn target was 44.7% with Zn-biofortified cultivars but only 24% with non-fortified cultivars. The likelihood of achieving the Fe target (59 mg kg^-1) was <8% across bread and durum wheat grain samples. Relative to nitrogen, phosphorus and potassium fertilizers, co-application of Zn and Fe increased grain Zn, Fe and protein concentrations by 27%, 41% and 25%, respectively. Combining agronomic and genetic biofortification is essential for improving grain nutrient concentrations and addressing micronutrient deficiencies.