Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/28/2004
Publication Date: 3/1/2005
Citation: Welch, R.M., House, W.A., Monasterio, I., Cheng, Z. 2005. Potential for improving bioavailable zinc in wheat grain (triticum sp.) through plant breeding. Journal of Agricultural and Food Chemistry. 53:2176-2180. Interpretive Summary: Over 30% of the world's population may suffer from zinc deficiency especially among resource-poor women and children resulting in increased mortality and morbidity rates and decreased cognitive function causing significant negative impacts on national development efforts and suffering among those afflicted. Ways need to be developed that will increase the dietary amounts of bioavailable zinc in foods that target those groups at highest risk of developing zinc deficiency. Plant foods provide significant amounts of zinc, but there are questions concerning the bioavailability of zinc in staple plant foods such as the wheat. Wheat grain are important dietary sources of zinc for many resource-poor families globally. Improving the bioavailable amounts of zinc in wheat grain could contribute significantly to lowering zinc deficiency among high-risk groups. We determined the bioavailable amounts of zinc in the grain of various wheat genotypes considered for use in global plant breeding programs. Our results show large variation in bioavailable grain-zinc between wheat lines studied using a rat model. Genetic selection for wheat grain with more bioavailable zinc appears possible in wheat breeding programs, thus allowing a sustainable food-based approach to reducing zinc deficiency among target populations globally dependent on wheat as a staple food.
Technical Abstract: A "whole-body" radioassay procedure was used to assess retention and absorption by rats of Zn in mature kernels of whole grain wheat harvested from 28 genotypes (Triticum spp.) grown in nutrient solution supplied 65Zn. Grain-Zn concentration differed between genotypes and ranged from 33 to 149 ug g-1 dry weight (DW); similarly, grain-Fe concentration varied about four-fold, from 80 to 368 ug g-1 DW. Concentrations of Zn and Fe in the grain were positively correlated. Therefore, selecting genotypes high in grain-Zn also tends to increase grain-Fe concentration. Concentrations of myo-inositolhexaphosphate (phytate) in the wheat grain varied from 8.6 - 26.1 umol g-1 DW. Grain intrinsically labeled with 65Zn was incorporated into test meals fed to Zn-depleted rats. All rats readily ate the test meals so that Zn intake varied directly with grain-Zn concentration. As determined by the % of 65Zn absorbed from the test meal, the bioavailability to rats of Zn in the wheat genotypes ranged from about 60 to 82%. The amount of bioavailable Zn (ug) in the grain was positively correlated to the amount of Zn accumulated in the grain. There was a significant negative correlation between grain-phytate levels and % Zn absorbed from the wheat grain but the effect was not large. These results demonstrate that concentrations of Zn in whole-wheat grain, as well as amounts of bioavailable Zn in the grain, can be increased significantly by using traditional plant breeding programs to select genotypes with high grain-Zn levels. Increasing the amount of Zn in wheat grain through plant breeding contrivances may contribute significantly to improving the Zn status of individuals dependent on whole grain wheat as a staple food.