Elevated zinc concentration in zeaxanthin-biofortified sweetcorn kernels compared with a commercial hybrid

A glasshouse experiment was conducted to assess the potential for increasing sweetcorn (Zea mays L. var. rugosa) kernel zinc (Zn) concentration. Uptake of Zn was compared between a standard commercial supersweet variety ‘Hybrix 5’ and a zeaxanthin-biofortified variety ‘High zeaxanthin 103146’. The plants were grown in potted soil culture using a Vertisol soil, and five rates of Zn (0, 0.75, 1.5, 3 and 6 kg Zn ha^‑1) applied as ZnSO₄.7H₂O. Cobs were harvested at the appropriate maturity for sweetcorn eating, three weeks after pollination. On a fresh weight (FW) basis, the kernel Zn concentration in ‘High zeaxanthin 103146’ (7.11±0.21 mg Zn kg^‑1) was ca. three times that of ‘Hybrix 5’ (2.57±0.20 mg Zn kg^‑1) (p<0.001). The higher Zn concentration of ‘High zeaxanthin 103146’ was also significant in other plants parts, although not to the same extent as in kernel concentration. There was no effect of soil Zn fertilisation within the range of concentrations tested on increasing tissue Zn concentration of any plant part. Interestingly, the pollination of ‘High zeaxanthin 103146’ was generally poorer than ‘Hybrix 5’, resulting in lower kernel numbers per cob. Pollination differences may have contributed to the higher Zn concentration in ’High zeaxanthin 103146’ by reducing inter-kernel competition for Zn transported into the cob. The results show that sweetcorn kernels can potentially accumulate higher Zn concentrations and sweetcorn may be a useful target crop for Zn biofortification, while the lack of a soil Zn fertilisation effect suggests that genetic biofortification may be more effective in achieving elevated Zn concentrations in sweetcorn kernels.