Recurrent Selection for Phytic Acid Content in Maize Grain.

Phytic acid is the chemical form in which much seed phosphate is stored.  In the diets of monogatstric animals and humans it is poorly digested, leading to of large amounts of phosphorous in waste.  This high level of phosphorous is an environmental concern because it can lead eutrophication of lakes and streams.  Phytic acid also amplifies dietary mineral deficiencies, especially iron, because it chelates these ions, reducing their bioavailability.  For these reasons, there is interest in developing low phytic acid crops.   Several approaches to developing grain with low phytic acid have been used.  Transgenic approaches have allowed phytase, a phytic acid degrading enzyme, to be produced in the grain of transgenic plants.  Several low phytic acid mutants have been identified and mutation breeding has successfully reduced phytic acid levels in several crop species, but this approach can result in poor seed quality.  A quantitative, inexpensive, relatively high-throughput chemical assay exists for phytic acid and this assay has been used to show genetic variation exists in corn germplasm for grain phytic acid content.  We have initiated a breeding program in which we used divergent mass selection in two random-mated maize populations to alter phytic acid levels.  After two cycles of selection, the mean phytic acid levels are diverging as expected in both populations.