Effects of Cysteine and Inorganic Sulfur Applications at Different Growth Stages on Grain Protein and End-Use Quality in Wheat

The aim of this study was to test the significant effects of inorganic sulfur and cysteine on grain protein and flour quality in wheat and to provide a theoretical basis of wheat cultivation techniques with high yield and quality. In the field experiment, a winter wheat cultivar, Yangmai 16, was used, and five treatments were established, i.e., S₀ (no sulfur fertilizer application during the whole wheat growth period), S(B)₆₀ (60 kg ha⁻¹ inorganic sulfur fertilizer was applied as the basal fertilizer), Cys(B)₆₀ (60 kg ha⁻¹ cysteine sulfur fertilizer was applied as the basal fertilizer), S(J)₆₀ (60 kg ha⁻¹ inorganic sulfur fertilizer was applied as the jointing fertilizer), and Cys(J)₆₀ (60 kg ha⁻¹ cysteine sulfur fertilizer was applied as the jointing fertilizer). The fertilizer application at jointing stage showed a better influence than basal fertilizer application on protein quality; for the content of albumin, gliadin, and high molecular weight glutenin (HMW-GS), Cys(J)₆₀ was the best among these treatments. An increase of 7.9%, 24.4%, 43.5%, 22.7% and 36.4% was found in grain yield, glutenin content, glutenin macro-polymer (GMP), low molecular weight glutenin (LMW-GS), and S content under Cys(J)₆₀, in relation to the control, respectively. A similar trend was found in the end-use quality, as exemplified by an increase of 38.6%, 10.9%, 60.5%, and 109.8% in wet gluten content, dry gluten content, sedimentation volume, and bread-specific volume, respectively; a decrease of 69.3% and 69.1% in bread hardness and bread chewiness was found under Cys(J)₆₀. In terms of application period, topdressing at jointing stage is compared with base fertilizer, the sulfur fertilizer application at jointing stage showed larger effects on grain protein and flour quality, from the different types of sulfur fertilizer, the application of cysteine performed better than the use of inorganic sulfur. The Cys(J)₆₀ exhibited the best effects on protein and flour quality. It was suggested that sufficient sulfur application at jointing stage has the potential to enhance the grain protein and flour quality.