Efficient promotion of the nutritional and processing quality of wheat grain by Zn forliar spraying at 5 days after anthesis

Objectives Zn is one of the essential trace elements to wheat growth and development. The objective of our study was to investigate the effect of zinc application on grain quality of wheat.

Methods Field experient was conducted in 2013–2014 and 2014–2015 using wheat cultivar ‘Yangmai 16’ as materials. There were three treatments, no Zn fertilizer (CK), spraying Zn at the jointing stage (JS) and spraying Zn at 5 days after anthesis (5DAA). The Zn accumulation, grain nutritional quality and processing quality were determined.

Results Compared to CK, spraying Zn significantly increased Zn contents in wheat flour, and the increments were 27.2% and 57.8% in treatments of spraying Zn fertilizer at JS and spraying Zn fertilizer at 5DAA, respectively. Spraying Zn promoted the accumulation of nitrogenous substances, the contents of total protein, protein components, glutenin polymer (GMP), high molecular weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) were significantly increased (P < 0.05). The total grain protein contents were increased by 4.2% and 10.3% in the treatments of spraying Zn fertilizer at JS and at 5DAA, respectively. The nitrogen contents of stems, leaves, glumes and grains at the maturity were also increased by Zn, especially in the treatment of spraying Zn fertilizer at 5DAA (P < 0.05). Spraying Zn fertilizer also significantly increased dry gluten content and wet gluten content in flour. The dry gluten contents in the JS and 5DAA treatments were increased by 17.3% and 23.9%, respectively, and the wet gluten contents were increased by 15.4% and 20.1%, respectively. Meanwhile, Zn also increased the bread volume, with increments of 16.3% and 20.0% in the treatments of JS and 5DAA. The hardness and chewiness were decreased markedly. The decrements in hardness were 13.5% and 26.2%, and the decrements in chewiness were 6.8% and 24.3%, respectively.

Conclusions Forliar spraying of Zn can improve wheat grain quality, and the effect is more significant when sprayed at the grain filling stage, ie. 5 days after anthesis. The main reason is that later Zn application is more efficient in promoting assimilated nitrogen accumulation in wheat grain after anthesis.