Distribution of the stable isotopes 57Fe and 68Zn in grain tissues of various wheat lines differing in their phytate content
Background and aims
Cereals are an important source of iron (Fe) and zinc (Zn) for humans, but their concentrations are generally low in white flour (which corresponds to the starchy endosperm) and their bioavailability is limited by high phytate content in the bran. The aim of this study was to investigate whether the phytate content of wheat grain affects the distribution of Fe and Zn to the bran and starchy endosperm.
The stable isotopes 57Fe and 68Zn were applied to the flag leaves of four wheat lines differing in their phytate content. The isotopes were also applied to roots of a low phytate line. Isotopic compositions in bran, starchy endosperm and straw were quantified by inductively coupled plasma mass spectrometry.
The low phytate line contained approximately half of the phytate-phosphorus concentration of the other three lines. Foliar applications of 57Fe and 68Zn increased the isotopic ratios 57Fe/56Fe and 68Zn/66Zn more in the bran than in the starchy endosperm. The low phytate line did not have a greater distribution of the isotope labels toward the starchy endosperm. The four wheat lines differed in the distribution of 57Fe and 68Zn from the flag leaves to the rest of the vegetative tissues and the grain. Little of the isotopes applied to roots at the anthesis stage reached the grain.
57Fe and 68Zn were preferentially distributed to the bran of wheat grain. Low phytate content in the bran does not appear to facilitate the distribution of 57Fe and 68Zn into the starchy endosperm.
KeywordsIron Zinc Stable isotopes Phytate Wheat grain
This research was funded by HarvestPlus Project 8055, “Optimizing the quality, species and availability of Fe in modern bread wheat cultivars in order to prevent global Fe deficiencies”. We thank Adrian Crosland and Steve Freeman for ICP analysis and to Drs. Edward Souza, Jianli Chen and Juliet Marshall (University of Idaho) for providing wheat lines and advice. Yanfang Xue acknowledges funding by the China Scholarship Council and High-Level Talents and Innovative Team Recruitment Program of Shandong Academy of Agricultural Sciences. Research in F. J. Zhao’s group is partly funded by the Innovative Research Team Development Plan of the Ministry of Education of China (grant no. IRT1256), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). Rothamsted Research receives strategic funding from the Biotechnological and Biological Sciences Research Council (BBSRC).
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