Genetic variability and stability of grain magnesium, zinc and iron concentrations in bread wheat

Four trials were conducted to study the grain magnesium (Mg), zinc (Zn) and iron (Fe) concentrations in bread wheat (Triticum aestivum L.). These trials used different sources of genotypes, including old French landraces, a worldwide germplasm collection and elite breeding lines or modern cultivars, grown in different environments. Mg concentration ranged from 600 to 1400 ppm in modern material, and reached 1890 ppm in some exotic genotypes. There was a negative correlation between grain yield and Mg concentration, but despite this dilution effect enough variability remains useful for selection purposes. Analysis of variance showed high genotype effects and Spearman rank correlations indicated moderate genotype by environment (G × E) interactions, so breeding for high Mg concentration can reasonably be envisaged. Zn concentration generally ranged from 15 to 35 ppm, but increased to 43 ppm in some genetic resources. Variation in Zn was also partly explained by a dilution effect. There was a significant effect of genotype, but also high G × E interactions, which would make direct selection more difficult than for Mg. However, as Zn and Mg concentrations appeared to be positively correlated, Zn concentration should respond favorably to selection for high Mg concentration. Fe concentration ranged from 20 to 60 ppm, and reached 88 ppm in non-adapted material. There were no significant genotype effects, very high G × E interactions, and the trait was poorly correlated to other mineral concentrations. Breeding for high Fe concentration will thus probably prove illusory.