Variation in zinc concentration of sweetcorn kernels reflects source–sink dynamics influenced by kernel number

Abstract

Grain yield and mineral nutrient concentration in cereal crops are usually inversely correlated, undermining biofortification efforts. Here, sink size, expressed as kernel number per cob, was manipulated by controlling the time when the silks of sweetcorn (Zea mays) cv. Hybrix 5 and var. HiZeax 103146 were exposed to pollen. Twelve other varieties were manually pollinated to achieve the maximum potential kernel number per cob, and kernel Zn concentration was correlated with kernel number and kernel mass. As kernel number increased, kernel Zn concentration decreased, with the decrease occurring to similar extents in the embryo tissue and the rest of the kernel. However, total kernel Zn accumulated per cob increased with increasing kernel number, as the small decreases in individual kernel Zn concentration were more than offset by increases in kernel number. When both kernel number and mass were considered, 90% of the variation in kernel Zn concentration was accounted for. Differential distribution of assimilates and Zn to sweetcorn cobs led to significant decreases in kernel Zn concentration with increasing kernel number. This suggests there will be challenges to achieving high kernel Zn concentrations in modern high-yielding sweetcorn varieties unless genotypes with higher Zn translocation rates into kernels can be identified.

Sweet Corn Research around the World 2015–2020

“…Furthermore, when the objective is to maximize nutrient production, some compromises are possible. Cheah et al [283] reported that, although there was a negative correlation between the number of kernels per cob and kernel Zn concentration, total kernel Zn accumulated per cob increased with increasing kernel number. Therefore, obtaining high kernel Zn concentrations and high yield in sweet corn is still a challenge.…”

Improved agronomic biofortification of sweetcorn achieved using foliar rather than soil Zn applications

“…Hybrix 5 and a high zeaxanthin experimental variety var. HZ 103146, chosen due to their differing capacity to accumulate Zn in plant tissues and their different yield potentials (Cheah, O′Hare, Harper, & Bell, 2020; Cheah, O′Hare, Harper, Kochanek, et al, 2020).…”

“…However, the considerably shorter period from pollination to harvest in sweetcorn (21–25 days) compared with maize (>50 days) suggests a narrower window for Zn accumulation and storage in kernels. A previous study also determined that Zn concentration is typically diluted in high‐yielding varieties with many kernels per cob (Cheah, O′Hare, Harper, & Bell, 2020).…”

Phosphorus partitioning contribute to phosphorus use efficiency during grain filling in Zea mays

“…P remobilization fluxes were calculated as the percentage of P in different organs to the grain P content. Micronutrient concentrations in the grains were determined (Cheah et al, 2020) and analyzed using inductively coupled plasma (Zasoski and Burau, 1977). Phytic acid (PA) concentration was determined as described by Haug and Lantzsch (1983).…”