Genotypic variability of grain phytic acid, mineral bioavailability, and their relation to foliar Zn application

Abstract

Phytic acid (PA) is the most prevalent storage form of grain phosphorus (P) and acts as an anti-nutrient by lowering mineral bioavailability. Genotypic variation of grain PA and its relation to mineral bioavailability, and their nutritional fortification potential with zinc (Zn) supply has not been fully investigated in pigmented rice. Here, we compared the differences in grain PA concentration and mineral bioavailability among 13 pigmented rice (red, yellow, and green rice) and six non-pigmented rice cultivars (three common white rice and their corresponding low-PA (lpa) mutant). Pigmented rice was enriched with micronutrients, especially Zn and Fe, on an average of 39.1 and 44.8 mg kg−1 as compared with 31.9 and 33.1 mg kg−1 in non-pigmented rice respectively. The lpa cultivars showed the highest bioavailability for most of the minerals. However, no significant difference was observed for mineral bioavailability between pigmented and common white rice, owing to higher anti-nutritional PA in pigmented rice (9.25 g kg−1) than in common white rice (8.29 g kg−1). However, a large difference in grain PA was found among green rice (11.19 g kg−1), yellow rice (9.82 g kg−1) and red rice (8.56 g kg−1) cultivars. Therefore, foliar Zn was used to investigate PA concentration and Zn bioavailability. Foliar Zn application increased grain Zn but decreased grain PA concentration, which ultimately increased grain Zn bioavailability. Zn application had a remarkable effect on Zn bioavailability for red rice (an average of 82%) as compared with common white rice (48%). These findings could provide helpful knowledge for pigmented rice fortification.