Iron and Zinc in Maize in the Developing World: Deficiency, Availability, and Breeding

Abstract

Maize (Zea mays L.) is the third most important cereal in the world and the most important food security crop in sub‐Saharan Africa. Maize provides energy and micronutrients. Deficiencies of the essential micronutrients Zn and Fe are fifth and sixth ranked among the top 10 most important risk factors for conditions such as anemia, low cognitive functioning, and impaired immune system (Fe deficiency) and diarrhea, skin inflammation, and recurrent infections (Zn deficiency) in humans, affecting more than two billion people worldwide. Poverty, lack of access to balanced diets and awareness, and low phytoavailability and bioavailability of these nutrients are major reasons for deficiencies. Breeding for mineral‐rich maize is a sustainable and cost‐effective approach to reduce micronutrient deficiencies. Since 2004, there has been significant progress in improving maize for Zn content. The aim of this review was to capture recent developments, trends, and progress in maize Fe and Zn biofortification and to identify challenges and ways to overcome them. HarvestPlus has set target levels for Fe (60 μg g−1) and Zn (38 μg g−1) in maize. Zinc target levels have been reached, but conventional breeding alone cannot enhance Fe to the recommended levels. Techniques such as oligo‐directed mutagenesis, reverse breeding, RNA‐directed DNA methylation, and gene editing could be used in future to speed up maize Fe biofortification. Additional research is required on Fe and Zn bioavailability in maize products, and on interactions of Fe and Zn with Ca and phytate and their influence on absorption, to better understand the underlying mechanisms.

A review of micronutrient deficiencies and analysis of maize contribution to nutrient requirements of women and children in Eastern and Southern Africa

“…But none of these approaches has been very successful in low-income countries (Stein 2010) because of lack of stable government policies and suitable infrastructure to distribute fortified food and supplements, and funding (Misra et al 2004). Therefore, breeding for mineralrich cereal crops such as maize by biofortification maybe a sustainable and cost-effective approach to lower MNDs (Akhtar et al 2018).…”

Stability Analysis and Heterotic Studies in Maize (Zea mays L.) Inbreds to Develop Hybrids With Low Phytic Acid and High-Quality Protein

“…Concomitantly, the GGE biplot also had similar results with CO 6, CO H(M) 8, DMR-QPM-09-13-1 × UMI 1099, and UMI 1205 × UMI 467 as stable high-yielding genotypes in the positive quadrant of the x-axis ( Figure 9A ). Also, as a confirmation for ideal hybrid in the GGE biplot, CO 6, CO H(M) 8, and DMR-QPM-09-13-1 × UMI 1099 were falling near the origin of the ideal axis (Akhtar et al, 2018 ). All the environments in the what-won-where plot for yield had a differential interaction toward the hybrids, and this states that other multilocational trials for yield could be conducted in larger plots across these places in the future ( Figures 9 , 10 ).…”

“…Hence, identifying stable hybrids with uniform genotype and environment (G × E) interactions by effective models such as Additive Main Effects and Multiplicative Interaction (AMMI) and Genotype main effect plus genotype-by-environment interaction (GGE) biplot enhances the selection for these traits in breeding trials. These numerical and graphical approaches in stability are predominantly used to discriminate the genotypes for response variable and mega environments graphically thereby locating stable lines in crop improvement programs (Akhtar et al, 2018;Vaezi et al, 2019). Speaking of both lpa and tryptophan in a hybrid, this is an initial program aimed to produce a high-yielding stable maize hybrid with a desirable lower PA and higher tryptophan content.…”

How can we breed for phosphate efficiency in maize (Zea mays)?

“…Hence, the breeding goals also have to adapt to different cultivation scenarios: While some regions of the world are challenged with very low soil P levels, for example, in sub‐Saharan Africa, intensively farmed regions like Europe are instead confronted with eutrophication due to overfertilization (Withers et al, 2019). In the first case, low P concentrations in the harvested grain are desirable because soil P mining should be avoided (Leiser, Rattunde, Weltzien, & Haussmann, 2014) and P in the form of phytate negatively interacts with the uptake of other minerals and some micronutrients (Akhtar et al, 2018; Lux et al, 2022). In the case of high soil P levels, additional inputs in these sufficiently supplied agricultural soils should be reduced (Weiß et al, 2021).…”