Effects of source/sink manipulation on grain zinc accumulation by winter wheat genotypes

Abstract

Agronomy practices aimed at wheat (Triticum aestivum L.) grain Zn biofortification are important to alleviate Zn deficiency in humans, especially for those resource-poor people owing to subsistence on diets dominated by cereal-based foods with low concentrations and bioavailability of Zn. To promote understanding of source-sink flow processes affecting biofortification of wheat with Zn, effects of different source/sink manipulations on grain Zn accumulation by wheat were examined in pot and field at two locations. Treatments included foliar applications of deionized water, sucrose, ZnSO4, sucrose + Zn, defoliation, spike shading or partial removal of spikes. Results showed sucrose + Zn significantly increased grain Zn concentration more than Zn alone. Grain Zn concentration with sucrose + Zn averaged 66 mg kg-1 for ‘Kenong 9204’ and 59 mg kg-1 for ‘Liangxing 99’ in pot, and ranged from 42 to 58 mg kg-1 for ‘Liangxing 99’, ‘Jinan 17’, ‘Jimai 20’, ‘Jimai 22’, and ‘Luyuan 502’ under field, approaching the field-grown target 60 mg kg-1 proposed by World Health Organization. Molar ratios of phytic acid/Zn and phytic acid × Ca/Zn of ‘Jinan 17’, ‘Jimai 20’ or ‘Luyuan 502’ with sucrose + Zn were reduced to be < 15 and < 200, respectively, suggesting higher Zn bioavailability. Defoliation or spike shading decreased grain weight, Zn concentration and content. It is concluded that grain Zn accumulation of wheat can be affected by the source-sink relationship of Zn and/or carbohydrate, and the foliar spray ‘sucrose + Zn’ is recommended for increasing concentration and bioavailability of Zn in wheat grains.