Elsevier

Journal of Cereal Science

Volume 50, Issue 3, November 2009, Pages 392-397
Journal of Cereal Science

Genetic variation of bioavailable iron and zinc in grain of a maize population

https://doi.org/10.1016/j.jcs.2009.06.014Get rights and content

Abstract

More than one-third of the world's population is afflicted by iron (Fe) and zinc (Zn) deficiencies, since cereal grain as a staple food of the people contains low levels or low bioavailability of Fe and Zn because of phytate. In maize, 80% of grain phosphorus (P) is in the form of phytate, and P could be an indicator of phytate content. The objectives of this study were (1) to estimate genetic variation of Fe and Zn in a maize population including P/Fe and P/Zn molar ratios as quantitative traits; (2) to determine relations among yield, P, Fe, Zn, P/Fe and P/Zn molar ratios; and (3) to define the implications of those on biofortification (breeding) programmes. There were significant genetic variations and workable heritabilities for Fe, Zn, P/Fe and P/Zn estimated in 294 F4 lines of a maize population, but there were no associations among six traits according to both simple correlations and principal component analysis. Weak correlations between P and Fe and between P and Zn indicated feasibility of breeding non low-phytic acid maize genotypes with more appropriate phytate/Fe and phytate/Zn relations. Bioavailability of iron and zinc varied substantially in a maize population justifying utilisation of these unique parameters in biofortification programmes.

Introduction

More than one-third of the world's population is afflicted by iron (Fe) and zinc (Zn) deficiencies, these ranking fifth and sixth among the ten most important risk causes of illness and disease in low-income countries (WHO, 2002). Among strategies for enhancing iron and zinc levels in cereal grains, plant breeding strategy (biofortification) appears to be the most sustainable and cost-effective approach (e.g. Cakmak, 2008, Graham et al., 1999, Welch and Graham, 2002). However, there are inherently low iron and zinc concentrations in cereal grains whose utilisation in the human digestive tract was additionally limited by substances that influence the bioavailability of these nutrients.

Bioavailability can be defined as the proportion of the total amount of mineral element that is potentially absorbable in a metabolically active form (House, 1999). Unrefined cereals contain high levels of phytate (myo-inositol hexaphosphate), known to be a powerful inhibitor of iron and zinc absorption in both adults (Egli et al., 2004, Mendoza et al., 1998) and children (Davidsson et al., 2004). Lönnerdal (2002) demonstrated that any reduction in dietary phytate can have a positive effect on zinc absorption. The same can be true also for iron (Mendoza et al., 1998). Thus, the negative effect of phytate on iron and zinc absorption follows a dose dependent response, and the phytate/iron or phytate/zinc molar ratio of a diet may be used to predict the proportion of absorbable dietary iron and zinc. Gibson (2006) has stated that particularly high phytate/zinc molar ratios are in diets of children from Malawi, Kenya, Mexico and Guatemala who consume only unfermented maize products.

There are low-phytate strains in maize (Raboy et al., 2000), but they express some less favourable agronomic features, e.g. reduction of seedling vigour (Bänziger and Long, 2000). Phytate also has some beneficial effects such as inhibition of different types of cancers (Somasundar et al., 2005, Vucenik and Shamsuddin, 2003). Therefore, biofortification programmes usually do not include decreasing phytate as a breeding objective beyond naturally occurring variability (Ortiz-Monasterio et al., 2007 for HarvestPlus programme).

The total phosphorus (P) in maize grain could be an indicator of phytate since 80% of the P is in the form of phytate (Raboy, 1997). Hence, identifying the relation between phosphorus and iron as well as between phosphorus and zinc concentrations in standard maize strains could be a way of increasing iron and zinc bioavailability in maize grain. There are several published studies about genetic variation of iron and zinc in grain of maize (Ortiz-Monasterio et al., 2007 for a review), but a thorough quantitative-genetic analysis for these traits is still lacking. Furthermore, there was no attempt to include bioavailability quantitatively to biofortification studies of iron and zinc. The objectives of this study were (1) to estimate genetic variation of iron and zinc in a maize population including P/Fe and P/Zn molar ratios as quantitatively inherited traits; (2) to determine relations between yield, phosphorus, iron, zinc, P/Fe and P/Zn ratios; and (3) to define the implications of those on biofortification programmes in maize.

Section snippets

Materials

As part of a biofortification project in maize at the Agricultural institute Osijek, Croatia, two temperate maize elite dent inbred lines having significantly different micronutrient concentrations according to our previous studies (Brkić et al., 2003, Brkić et al., 2004) were crossed in order to commence genetic studies. The two inbred lines (B84 and Os6-2) belong to opposite gene pools of U.S. Corn Belt germplasm: the line B84 is a well known BSSS line, while OS6-2 is related to the line C103

Results

There were significant differences between the means at two environments for all traits except iron (Table 1). Generally, there were higher yields, phosphorus and iron concentrations, as well as P/Fe and P/Zn molar ratios in 2006. Only zinc concentrations were significantly lower for 4.86 mg/kg in 2006 compared to 2005. Means of individual F4 lines varied significantly for all six traits, differing in 6.24 t/ha for yield, 1011 mg/kg for phosphorus, 16.95 mg/kg for iron, 12.21 mg/kg for zinc,

Discussion

Quantities of minerals in grain are influenced by numerous complex factors including genotype, soil properties, environmental conditions and nutrient interactions (House, 1999). Our study demonstrated that mineral concentrations of grain were affected by environmental conditions and year to some extent. However, if there were no adverse soil chemical properties (Cakmak, 2008 for review) or extreme weather conditions like in our study, differences among genotypes in absorbing sufficient amounts

Acknowledgments

The authors thank I. Kadar and J. Koncz at the Laboratory of the Research Institute for Soil Science and Agricultural Chemistry of Hungarian Academy of Science and Arts in Budapest, Hungary for ICP-OES analyses.

References (43)

  • I. Brkić et al.

    Genotypic variability of micronutrient element concentrations in maize kernels

    Cereal Research Communication

    (2004)
  • I. Cakmak

    Enrichment of cereal grains with zinc: agronomic or genetic biofortification?

    Plant Soil

    (2008)
  • L. Davidsson et al.

    Dephytinisation of soyabean protein isolate with low native phytic acid content has limited impact on mineral and trace element absorption in healthy infants

    British Journal of Nutrition

    (2004)
  • G. Drakakaki et al.

    Endosperm-specific co-expression of recombinant soybean ferritin and Aspergillus phytase in maize results in significant increases in the levels of bioavailable iron

    Plant Molecular Biology

    (2005)
  • D.S. Falconer et al.

    Introduction to Quantitative Genetics

    (1996)
  • R.S. Gibson

    Zinc: the missing link in combating micronutrient malnutrition in developing countries

    Proceedings of Nutrition Society

    (2006)
  • R.P. Glahn et al.

    Inhibition of iron uptake by phytic acid, tannic acid, and ZnCl2: studies using an in vitro digestion/Caco-2 cell model

    Journal of Agricultural and Food Chemistry

    (2002)
  • A.R. Hallauer et al.

    Quantitative Genetics in Maize Breeding

    (1988)
  • K. Liu et al.

    Genetic structure and diversity among maize inbred lines as inferred from DNA microsatellites

    Genetics

    (2003)
  • B. Lönnerdal

    Phytic acid–trace element (Zn, Cu, Mn) interactions

    International Journal of Food Science & Technology

    (2002)
  • A. Morgounov et al.

    Iron and zinc grain density in common wheat grown in central Asia

    Euphytica

    (2007)
  • Cited by (53)

    • New approaches, bioavailability and the use of chelates as a promising method for food fortification

      2022, Food Chemistry
      Citation Excerpt :

      While the second is bio-fortification, referred to as the method of increasing the concentration of micronutrients in the edible part of the plant. Bio-fortification is obtained by 2 means, either by the addition of fertilizers and the stimulation to absorb these minerals by the plant, or by plant breeding, considered to be the most sustainable and cost-effective approach (Hunt, 2002; Ikuli et al., 2019; Romina Alina et al., 2019; Rosell, 2016; Šimić et al., 2009). It was found that the usage of micronutrient fertilizers was effective in increasing the concentration of these nutrients in the plant (Romina Alina et al., 2019).

    • Identifying key drivers for geospatial variation of grain micronutrient concentrations in major maize production regions of China

      2020, Environmental Pollution
      Citation Excerpt :

      The similar results about wheat were widely reported, including China (Liu et al., 2014), England (Fan et al., 2008), Hungary (Zhao et al., 2009) and America (Guttieri et al., 2015). Thus, the relatively higher grain yield of maize in China (ranging from 3.17 to 15.48 t ha−1, average 8.39 t ha−1) might be a crucial cause of the lower grain micronutrient concentrations compared with other countries (Šimic et al., 2009; Banziger and Long, 2000). However, the yield dilution effect may not necessarily have occurred, and the relation might be affected by specific environmental conditions (Banziger and Long, 2000).

    View all citing articles on Scopus
    View full text