Speciation and accumulation of Zn in sweetcorn kernels for genetic and agronomic biofortification programs

Genetic and agronomic biofortification of zinc in sweetcorn

“…3.12). This expands the findings of a previous XAS study which only examined sweetcorn at a single level of maturity in a market survey (Chapter 3.2, (Cheah et al, 2019a)) to include maize varieties. The high proportion of Zn-phytate within the embryo is also consistent with previous studies reporting that most of the maize phytate content is found in the embryo (O'Dell, 1972).…”

“…Having established the suitability of sweetcorn as a target crop for Zn biofortification, this chapter explores the interactions between genotype and environment that influence the Zn concentration in sweetcorn kernels. Although there is reported data on Zn concentration in mature maize kernels (Lin et al, 2005, Long et al, 2004, Oikeh et al, 2004, few studies have examined Zn concentration in immature kernels of sweetcorn (Warman and Havard, 1998, Cheah et al, 2019a, Cheah et al, 2019b, Cheah et al, 2020. The aim of this study was to quantify immature kernel Zn concentrations across a range of commercial yellow sweetcorn varieties, and contrast this with concentrations in other Zea mays germplasm, including starchy maize lines.…”

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

“…Given the importance of speciation to the bioavailability of Zn for absorption after consumption, the allocation of Zn between embryo and endosperm tissues will be an important factor in securing desired biofortification outcomes. This is important because of the contrasting Zn concentrations ( Table 2 ) in these kernel constituents and their bioavailability: Zn in embryo tissues is stored predominantly as Zn phytate, which has low bioavailability for humans, whereas Zn stored in the endosperm is complexed with N- or S-containing ligands and has higher bioavailability ( Cheah et al , 2019a ). In addition, the stability of the Zn allocation between kernel constituents in response to increasing source limitations caused by increasing kernel number will be particularly important for breeding programmes seeking to improve both yield and bioavailable Zn content in sweetcorn.…”

“…This micronutrient-rich embryo is typically removed during the processing of maize kernels by dry milling, whereas the entire kernel of sweetcorn is consumed. This potential dietary advantage of sweetcorn is negated by the fact that most of the Zn in the embryo is in the form of Zn phytate, which is not bioavailable to humans ( Cheah et al , 2019a ); by contrast, the Zn accumulated in the endosperm has been shown to be mostly bioavailable. Therefore, to achieve a beneficial outcome for human health, genotypes that accumulate Zn in the endosperm are preferable to those that accumulate Zn in the embryo.…”

New Insights to Zinc Biofortification of Wheat: Opportunities to Fine-tune Zinc Uptake, Remobilization and Grain Loading

“…These compounds include non-proteinogenic amino acids such as nicotianamine (NA) [2(S),3'(S),3"(S)-N-[N(3-amino-3-carboxypropyl)-3-amino-3-carboxypropyl] azetidine-2carboxylic acid], that are derived from NA including the mugineic acid family phytosiderophores (MA) and 2'-deoxy mugineic (DMA) amino acids (Clemens, Deinlein, Ahmadi, Horeth, & Uraguchi, 2013;Sinclair & Kramer, 2012), including histidine and cysteine (Cheah et al, 2019;Cheah, Kopittke, Scheckel, Noerpel, & Bell, 2020), organic acid-carboxylates including malate and citrate (Haydon & Cobbett, 2007), peptides (Clemens, 2019;Lemmens et al, 2019), as well as small proteins (metallothioneins) (Leszczyszyn & Blindauer, 2010) (Figure 1).…”