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Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin



G. Velu, I. Ortiz-Monasterio, R.P. Singh and T. Payne
 
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ABSTRACT

Micronutrient malnutrition, resulting from dietary deficiency of important minerals such as zinc (Zn) and iron (Fe), is a widespread food-related health problem. In a recent initiative of CGIAR’s HarvestPlus challenge program is embarked upon to address this issue through the development of biofortified cultivars with elevated levels of these micronutrients in common wheat (Triticum aestivum L.). Genetic enhancement mainly depends on existence of genetic variability available in the gene pool. Hence, the magnitude of variability for grain Zn and Fe concentrations were studied in 600 wheat core-collection accessions of diverse origin. Grain Zn concentrations among the accessions ranged from 16.85 to 60.77 mg kg-1 and Fe concentrations ranged from 26.26 to 68.78 mg kg-1. The highest levels of Zn concentrations were observed in a Chinese spring bread wheat accessions HONG DUAN MANG and highest Fe concentration was observed in a accession originated from Spain ‘ANDALUCIA 344‘. Top ranking accessions with high Zn and Fe concentrations are being evaluated for multi-locational testing to study the expression of these micronutrients in target countries, also these accessions are being used as potential donor for further germplasm improvement at International Maize and Wheat Improvement center (CIMMYT), Mexico. There was a highly significant and positive correlation between Zn and Fe concentrations (r = 0.81; p<0.01), indicating simultaneous improvement of both of the micronutrients would be effective and high Fe and Zn sources identified in this study provide a valuable genetic resource for breeding cultivars with high Zn and Fe concentrations.

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  How to cite this article:

G. Velu, I. Ortiz-Monasterio, R.P. Singh and T. Payne, 2011. Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin. Asian Journal of Crop Science, 3: 43-48.

DOI: 10.3923/ajcs.2011.43.48

URL: https://scialert.net/abstract/?doi=ajcs.2011.43.48
 
Received: November 05, 2010; Accepted: December 20, 2010; Published: March 25, 2011



INTRODUCTION

Micronutrient malnutrition arising from zinc (Zn) and iron (Fe) deficiency has emerged as a serious health problem worldwide, affecting more than two billion people worldwide (Welch and Graham, 2004). The most prevalent deficiencies for these micronutrients occur particularly among pregnant women and children in resource poor families of developing countries (WHO, 2002). Of these, Fe is of the most importance, with approximately three billion people suffering from Fe deficiency related aneamia (United Nations System Standing Committee on Nutrition, 2004). The global average prevalence of Zn deficiency has been estimated to be 31%, with the most severe expressions in Africa and South Asia. Its deficiency is known to significantly increase the risk of many diseases viz., diarrhea, pneumonia, and malaria, therefore Zn deficiency has been linked to the morbidity and mortality of children.

A major factor causing Zn and Fe deficiency is their low bioavailability in diets based on cereals and legumes. Thus, it is important to improve the micronutrient quality of staple foods by increasing the levels of Zn and Fe concentrations. Bread wheat (Triticum aestivum L.) is a highly consumed cereal crop. On a worldwide scale, it contributes approximately 30% of the total cereal production, making it a major source of minerals for many people (McKevith, 2004). Wheat is also one of the most important food crops in South Asia, as this region is being targeted for initial release and commercialization of biofortified wheat, especially in the area around Indo-Gangetic plains, a region with high population densities and high micronutrient malnutrition. So it is imperative to develop wheat cultivars with improved Zn and Fe concentrations to alleviate malnutrition around the world.

Genetic enhancement of crop cultivars with elevated levels of these micronutrients would be cost effective sustainable way of solving global micronutrient malnutrition problem. Consequently, the Consultative Group on International Agricultural Research (CGIAR) launched the HarvestPlus initiative (http://www.harvestplus.org), a program focusing on breeding food crops with high micronutrient contents. Under this initiative, CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo, http://www.cimmyt.org) and partner institutions, are attempting to develop high yielding, disease resistant wheat (Triticum aestivum L.) germplasm with enhanced levels of Zn and Fe. Success in crop improvement through breeding depends on the existence of genetic variation for the target traits in the available gene pool. Hence, a representative sample of 600 gene bank wheat accessions were evaluated for grain mineral elements that could be explored in future wheat breeding programs. The main objective of the present study was to investigate the variation for micronutrient concentration in wheat grain among 600 core-collection accessions.

MATERIALS AND METHODS

A set of 600 bread and durum wheat accessions originated from more than twenty-five countries representing major wheat growing regions of the world were drawn from the genetic resources collection in the gene bank of CIMMYT-Mexico. These accessions were evaluated in a randomized complete block design (RCBD) with two replications at CIMMYT- Cd Obregon, Mexico. Each accession was grown in 2 rows of 2 m length at 0.75 cm spacing between the rows in 2005 crop season. The experiment received 120 kg ha-1 N (50% basal and 25% top dressed twice at third and seven weeks after sowing), 60 kg ha-1 P2O5 and 40 kg ha-1 K2O. Wheat grain was harvested at crop maturity and the grains cleaned of any glumes and inert matters. Grain samples were analyzed for mineral concentration at Waite Analytical Services, University of Adelaide, Australia, based on the nitric/perchloric acid digestion method using an inductively coupled plasma optical emission spectrometer (ICP-OES) (Zarcinas et al., 1987).

RESULTS AND DISCUSSION

The concentrations of 15 minerals in wheat grain were determined. For brevity, only the data of two trace elements (Zn and Fe) that are of particular importance to human nutrition are presented in this paper. Among the 600 accessions, grain Zn varied by 3.6-fold, ranged from 16.85 to 60.77 mg kg-1 with the mean of 30.41 mg kg-1 and, grain Fe concentrations varied by 2.6-fold, ranging from 26.26 to 68.78 mg kg-1 with the mean of 39.65 mg kg-1 (Table 1, Fig. 1). Analysis of variance showed highly significant differences existed among entries for Zn concentration and contents (Table 2). Nine accessions (50.95-60.77 mg kg-1) had > 50 mg kg-1 Zn concentrations. The highest Zn concentrations were observed in a Chinese accessions ‘HONG DUAN MANG’ followed by a Turkish accession ‘AKSEREZ’, and these accessions are being used as potential donor for germplasm improvement at CIMMYT.

Table 1: Core-collection accession with high Zn and Fe concentrations (>mean+2 SD), Cd. Obregon, Mexico
Image for - Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin
1, 2 and 3 are accessions with >mean+2SD for Zn concentration, Fe concentration and common for both Zn and Fe concentrations, respectively

Top ranking accessions with high Zn and Fe concentrations are being evaluated in replicated trials in Mexico, also in target countries to study their Genotype x Environment interaction for expression of these micronutrients.

A large and highly significant difference among the accessions was also found for Fe concentration and content. Thirty-five accessions (50.12-68.78 mg kg-1) had grain Fe concentrations >50 mg kg-1, ‘ANDALUCIA 344’ accession originated from Spain had highest grain Fe, followed by a accession from USA ‘PI352426” and then, Turkish accession ‘AKSEREZ’ (second ranked for Zn concentrations).

Image for - Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin
Fig. 1: Frequency distribution of grain Zn and Fe concentrations in core-collection accessions

Image for - Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin
Fig. 2: Relationship between grain Zn and Fe concentrations in core-collection accessions

This was expected considering a highly significant and positive correlation between Fe and Zn concentration (r = 0.81; p<0.01) (Fig. 2). Similar relationship between Fe and Zn have been reported in maize (Dixon et al., 2000), rice (Zhang et al., 2004) and wheat (Ortiz-Monasterio et al., 2007), indicating that selection for either Fe or Zn will lead to correlated selection response for the other micronutrient.

In total, 89 accessions showed grain Fe concentrations above mean+1 SD for Fe and 19 accessions had above mean+2SD. For Zn, 83 accessions showed above mean+1 SD and 27 accessions had above mean+2SD. Of these, there are 13 accessions are common for both Zn and Fe concentrations with mean+2 SD, indicating close relationship between the Zn and Fe concentrations. Table 1 also provides total amount of Zn and Fe per seed (content). Large variation was observed for Zn (0.49-2.06 μg grain-1) and Fe content (0.63-2.38 μg grain-1) indicates large differences for seed weights among accessions. For example, the accession ‘PI 352426’ with a second highest concentration of Fe (>65.80 mg kg-1) also had high seed weight (or seed size) and had, consequently the highest total amount of Fe (2.38 μg grain-1). A similar trend was observed for Zn.

Table 2: Analysis of variance for grain Zn and Fe concentrations and contents
Image for - Variation for Grain Micronutrients Concentration in Wheat Core-collection Accessions of Diverse Origin
*, ** Significant at 5 and 1% probability levels, respectively

There was a highly significant correlation between the concentration and content of Zn (r = 0.65; p<0.01) and Fe (r = 0.45; p<0.01) indicating accessions with high Zn and Fe concentrations also had greater grain weight, suggesting that higher grain Zn and Fe concentrations are not necessarily related to small grain size or weight.

Table 2 shows the Pearson correlations between Zn and Fe concentrations and content. A strong positive correlation was found between Zn and Fe concentrations (r = 0.81; p<0.01) and contents (r = 0.85; p<0.01) indicating simultaneous improvement is possible as these minerals accumulation controlled by common genetic factors. A very strong correlation between grain Fe and Zn concentrations with grain protein was also shown previously by Ortiz-Monasterio et al. (2007), indicating grain protein may be sink for Zn and Fe. Recent studies have shown that the Gpc-B1 (Grain protein content-B1) locus from wild emmer wheat affects both grain protein content and the concentrations of these minerals in grain (Distelfeld et al., 2007). This locus encodes an NAC transpiration factor (NAM-B1) that accelerates senescence and increases remobilization of nutrients (Fe, Zn, N) from leaves to developing grains (Uauy et al., 2006). This positive correlation between Zn and Fe concentrations and, with protein content would be useful information to develop wheat cultivars with high protein with highest Zn and Fe concentrations.

CONCLUSIONS

This research showed the existence of large variability for Zn and Fe concentrations among a diverse range of core-collection accessions. Top ranking accessions with high Zn and Fe concentrations would serve as a potential donor for further germplasm improvement with elevated micronutrients. High positive correlation between Zn and Fe indicates simultaneous selection would be highly effective. Genetic enhancement of grain Zn and Fe concentrations in wheat is being integrated with genetic improvement of grain yield, disease resistance and other agronomic traits at CIMMYT. In the pursuit of this objective, studies are underway to examine the association of grain Zn and Fe with grain yield and other agronomic traits.

ACKNOWLEDGEMENTS

This research was supported by a grant from HarvestPlus Challenge Program of the Consultative Group on International Agricultural Research (CGIAR).

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