Differences Of Grain Zn,Fe,Cu,Mn Content Among Wheat Varieties And Their Responses To Foliar Fertilization

In this study,field experiments were carried out using 138 wheat landraces and 154 wheat cultivars released in different eras.The differences of grain zinc,iron,copper and manganese contents and their bioavailability among wheat cultivars released in different decades,and also between wheat cultivars and landraces were analyzed.The effects of foliar zinc and iron application on the grain zinc and iron contents and their bioavailability were dicussed,and to provide information for the breeding and cultivation of wheat varieties rich in micronutrients.The main conclusions are as follows:1.The grain zinc(25.22～67.25 mg kg^-1),iron(25.91～59.80 mg kg^-1),copper(3.57～9.90 mg kg^-1),manganese(17.67～51.77 mg kg^-1),Phytic acid(9.02～14.59 mg g^-1)concentrations were significantly different among wheat varieties.The concentrations of zinc,iron,copper and manganese in grain changed more than twice.Overall,the grian zinc concentration of the tested wheat varieties was relatively high,and about 40%of the varieties had higher zinc concentration than the recommended zinc concentration of wheat grain(40 mg kg^-1),however,the grain iron concentration of the tested wheat varieties was relatively low,and only 8%of the tested varieties showed higher iron concentration that higher than the recommended concentration of iron(50 mg kg^-1).Great variation of major micronutrients and phytic acid concent among wheat varieties provides a wide range of germplasm resources for screening and cultivating wheat varieties rich in mineral nutrients.2.There were no significant differences in manganese content among cultivars released in different eras,and significant differences were observed in zinc,iron,and copper content.The grain zinc content increased slightly as the eras progressed,and the varieties released in the 1990s had the highest grain zinc concent and the varieties released between 1940s to 1960s had the lowed grain zinc content.The contents of iron and copper in wheat grains did not vary significantly before 1990s,and then decreased significant.The grain phytic acid content increased first and then decreased,and the varieties released in the 1970s had the highest grain phytic concent.As the eras progressed,phytic acid to zinc molar ratio decreased slightly,and phytic acid to zinc molar ratio did not vary significantly.The grain iron content of landrace was 12.8%higher that of cultivar,however,there were no significant differences between landraces and cultivars in terms of grain zinc,copper,and manganese.As compared with landraces and the cultivars released before1990s,the cultivars released after 1990s had the highest grain zinc content and the lowest iron content.The grain phytic acid of the cultivars were significantly lower than those of the cultivars.Overall,the cultivars released after the 1990s showed higher grain zinc content and lower grain iron content,compared with thost of cultivars released after the 1990s.The breeding of wheat varieties with more iron and copper in grains should be strengthened.There are more high-zinc and high-iron varieties among landrace,which are excellent wheat germplasm resources.3.Under foliar zinc application,the grain zinc content increased significantly by 8.4 mg kg^-1(44.4-52.8mg kg^-1),the phytic acid did not vary significantly,and the phytic acid to zinc molar ratio decreased significantly by 17.8%.Under foliar iron application,the grain iron content increased significantly by 1.9mg kg^-1(39.4～41.3 mg kg^-1),the phytic acid decreased by 2.8%,and phytic acid to iron molar ratio reduced by 7.9%.This indicated that foliar zinc application can significantly increase grain zinc content,reduce the phytic acid to zinc molar ratio,and improve zinc bioavailability,while foliar iron application does not significantly increase grain iron content and increase grain iron bioavailability.4.Under foliar zinc application,for both cultivars and landraces,the grain zinc content increased significantly,and the phytic acid to zinc molar ratio decreased significantly.Compared with no foliar zinc application,foliar zinc application increased the grain zinc content by 12.5 mg kg^-1（26.9%）and 6.6 mg kg^-1（15.3%）,and reduced the phytic acid to zinc molar ratio by 24.2%and 14.9%for landraces and cultivars,respectively.The grain iron content and iron bioavailability did not increased significantly with foliar iron application compared to no foliar iron application,and no significant differences in the grain iron content and iron bioavailability between the cultivars and landraces.Overall,under foliar zinc application,the grain zinc content and grain iron bioavailability increased more for landraces than for cultivars.For both cultivars and landraces,the grain iron content and iron bioavailability did not increased significantly with foliar iron application compared to no foliar iron application.This study revealed the differences of grain zinc,iron,copper,manganese contents among wheat varieties released in different eras,and clarified the regulatory effect of foliar zinc and iron application on the nutritional characteristics of zinc and iron in wheat grains,and provides theoretical information the breeding and cultivation of wheat varieties rich in micronutrients.