Zinc biofortification of immature maize and sweetcorn (Zea mays L.) kernels for human health

This study explores the potential for genetic biofortification of sweetcorn (Zea mays L.) by quantifying immature kernel zinc (Zn) concentrations across a broad range of Zea mays L. germplasm. Varieties examined included commercial sweetcorn cultivars, high zeaxanthin sweetcorns, purple sweetcorns, blue maize, quality protein maize and popcorns. Though all kernel samples were harvested at a physiologically immature stage typical of sweetcorn harvest and consumption (21 days after pollination, DAP), the varieties accumulated distinctly different kernel dry matter concentrations depending on whether they were classified as sugary or starchy varieties. The difference in dry matter concentration between types confounded comparisons of kernel Zn concentration when assessed on a fresh mass basis, which is typically used to quantify dietary intake. Kernel mass (indicative of kernel size) and the ratio of embryo-to-kernel mass also contributed to variation in kernel Zn concentration. Analysis of a broader range of nutrient concentrations suggested that variation in kernel Zn concentration was more closely associated with variations in S concentration than P concentration in the sugary varieties. This suggested the possibility of biofortifying sweetcorn kernel Zn without necessarily increasing kernel P and associated anti-nutrient compounds like phytate.