Improving the bioavailability of iron and zinc: low-phytate rice mutants
2003
Rasmussen, S. K. | Josefsen, L. | Leung, H. | Sorensen, M.B.
Cereal grains contain antinutritional factors that reduce the bioavailability of iron and zinc. Phytate has for a long time been known to lower the uptake of these and other minerals. In the cell, phytate is stored together with iron, zinc, and calcium as densely packed particles similar to protein storage bodies. It can be regarded as a phosphorus storage compound as, in fact, up to 80% of the grain phosphorus is bound in phytate, while the remaining is in nucleic acids and phospholipids and present as phosphate. Mutational breeding for low-phytate barley has shown that it is possible to substantially reduce the content of phytate in the grain while still maintaining high germinantion and grain yield. The grain content of minerals, for example, Fe, does not change in the mutant lines. Furthermore, feeding trials with small animals confirmed that bioavailability of iron and zinc is improved in low-phytate barley. From the knowledge gained with barley grain mutants, we have shown that the pathway to phytate is seed-specific and that biosynthesis of phytate in vegetative tissues and pollen is not affected by these mutations. Low-phytate mutants in rice have been isolated and the material currently in use consists of M4 seeds from diepoxybutane-treated IR64. Single grains from 144 rice accessions were extracted and tested for free phosphate by molybdate blue staining and two putative mutants were collected.
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