Assessment of the contents of phytic acid and divalent cations in low phytic acid (lpa) mutants of rice and soybean

The objective of the study was to investigate the influence of mutational breeding on the contents of nutritionally relevant minerals in low phytic acid (lpa) mutants compared to their wild-types. Three lpa rice (Os-lpa-XQZ-1, Os-lpa-XS110-1, Os-lpa-XS110-2) and two lpa soybean mutants (Gm-lpa-TW75-1, Gm-lpa-ZC-2) were analyzed regarding their contents of phytic acid, lower inositol phosphates and the minerals calcium, iron and zinc. Additionally, cadmium was included into the spectrum of divalent cations analyzed. The phytic acid reduction in lpa rice was consistently more pronounced in Os-lpa-XS110-1 than in Os-lpa-XQZ-1 and Os-lpa-XS110-2. However, only for Os-lpa-XQZ-1, levels of calcium, iron and zinc were found to be consistently increased, whereas the cadmium level was shown to be predominantly decreased compared to the wild-type. Investigation of the two lpa soybean mutants, characterized by absence (Gm-lpa-TW75-1) and accumulation (Gm-lpa-ZC-2) of lower inositol phosphates, respectively, revealed no consistently decreased or increased contents of calcium, iron, zinc and cadmium. The data do not change the view that lpa mutations do not result in systematic increases or decreases of mineral contents in these crops. However, on the basis of the molar ratios of phytate/minerals in lpa rice and soybean mutants which are considered as predictive parameters, an improved bioavailability of minerals in the lpa materials can be expected.