| Phytic acid is a chelating agent which binds minerals and makes them unavailable for dietary absorption. Zinc is an essential micronutrient for humans but its bioavailability in many cereal grains is low because of a high molar ratio of phytic acid to zinc, which is considered as an important parameter for evaluating zinc bioavailability in the human body. Phytate/zinc molar ratios above 15 are considered to indicate low bioavailability. In order to improve grain Zn bioavailability of local modern wheat, an experiment using foliar fertilizer application was conducted in Yangzhou, China. Winter wheat cultivar Yangmai 16, Yangmai 13 and Yangfumai 2, grown in a cement tank filled with clay loam soil, were treated by foliar Zn application at 3 rates of 0（control）, 0.2% and 0.4% of Zn as ZnSO4 solution at grain filling stage. The first Zn treatment was applied at 1 week after flowering（WAF）, the second and third application were at 2 and 3 WAF, respectively. The plants in control plots received clean water. The results showed without foliar Zn application, phytic acid（PA） concentrations in bran, shorts and flour of wheat grains were 19.4 mg·g-1, 5.3 mg·g-1 and 1.8 mg·g-1, respectively; Phytic acid concentration in bran was 11 times higher than in flour. Zinc application had no significant effect on PA concentration in different grain fractions. The Zn bioavailability indicator, the molar ratio of phytic acid to Zn（PA/Zn） showed that PA/Zn in flour was lower than that in shorts or bran. Compared with control treatment, 0.2% ZnSO4 foliar application at grain filling stage decreased PA/Zn in bran, shorts and flour by 37%, 44% and 43%, respectively; 0.4% ZnSO4 foliar application at grain filling stage decreased PA/Zn in bran, shorts and flour by 54%, 58% and 54%, respectively. Foliar Zn application after flower improved Zn bioavailability in different grain fractions through increasing Zn concentration in grains of modern wheat cultivars, which is a fast and effective biofortification approach to improve Zn nutrition in humans as well as animals. |
