Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/10/2006
Publication Date: 9/1/2006
Citation: Garvin, D.F., Welch, R.M., Finley, J.W. 2006. Historical shifts in the seed mineral micronutrient concentration of U.S. hard red winter wheat germplasm. Journal of the Science of Food and Agriculture. 86:2213-2220. Interpretive Summary: Given the importance of wheat as a crop for human subsistence, it is important to understand whether large yield improvements have negatively impacted the concentration of mineral micronutrients in the grain. We examined the seed concentrations of 4 essential mineral micronutrients in 14 U.S. wheat varieties released at different times during the period between 1874 and 1995. We found negative associations between seed mineral concentrations and yield that were significant approximately one-half of the time. Frequently, the oldest variety examined had higher concentrations of iron, zinc, and selenium than many of the newer varieties. Our results indicate that in some instances, newer and higher yielding U.S. wheats have lower levels of certain human mineral micronutrients. These results are significant because they indicate that breeding wheat to contain higher levels of mineral micronutrients, which has been proposed to reduce human micronutrient malnutrition, might reduce yields.
Technical Abstract: It is not clear what impact genetic gains in wheat (Triticum aestivum L.) yields have had on the concentration of human mineral micronutrients found in the grain. We compared seed iron (Fe), zinc (Zn), copper (Cu), and selenium (Se) concentrations in 14 U.S hard red winter wheat varieties from production eras spanning more than a century. The seed that was analyzed came from replicated field trials conducted at two locations in Kansas. The Fe, Zn, and Cu data were obtained by inductively coupled plasma emission spectroscopy (ICPES), and Se data were obtained by hydride-generated atomic absorption spectrometry (HG-AAS). Significant location effects on all micronutrient concentrations were detected. In all but one instance, significant differences between varieties for seed micronutrient concentrations were detected. Significant negative correlations between yield and seed Zn were detected at both locations (r = -0.62 and -0.85) and between yield and Fe at one location (r = -0.57). Our results suggest that genetic gains in yield in U.S. hard red winter wheats have resulted in significant reductions of seed Fe and Zn concentrations, with a similar trend observed for Se. However, the expression of this reduction is dependent on growing location.