Sulfur and nitrogen effects on winter wheat quality

Authors: WILSON, TARA - Kansas State University; NELSON, NATHAN - Kansas State University; FRITZ, ALLAN - Kansas State University; Guttieri, Mary; Tilley, Michael - Mike

Submitted to: AACC International
Publication Type: Abstract Only
Publication Acceptance Date: 3/16/2020
Publication Date: 4/1/2020
Citation: Wilson, T., Nelson, N., Fritz, A., Guttieri, M.J., Tilley, M. 2020. Sulfur and nitrogen effects on winter wheat quality. AACC International. https://doi.org/10.1016/j.jcs.2020.102969.
DOI: https://doi.org/10.1016/j.jcs.2020.102969

Interpretive Summary: Amino acid concentration, Grain Protein concentration and Grain Protein composition are all key factors in winter wheat quality. Asparagine is an essential amino acid precursor of protein in wheat grain. Any interruption in grain protein assembly in the developing seed can potentially increase asparagine concentration in harvested grain. In the preparation of some foods, asparagine is converted to acrylamide, which is a health concern. The SDS-SRC is a very important test because it shows the absorption of solvent in easy and timely way. Solvent retention correlated to our farinograph stability numbers. This research examined the role of sulfur and nitrogen fertilization in regulating final asparagine concentration in harvested grain of five winter wheat varieties grown on sulfur-deficient soil. Sulfur treatment increased solvent retention, farinograph stability and total protein content and composition. Nitrogen treatment and genotype also affected SDS-SRC, farinograph stability, protein content and composition and asparagine concentration. These results indicate that adequate sulfur fertility is an important component of producing wheat with higher overall quality.

Technical Abstract: Grain protein concentration and composition are key factors in winter wheat quality. Elevated asparagine concentration in wheat flour also can lead to acrylamide production in baked food products, which can be a health concern. Asparagine concentration represents the acrylamide-forming potential of flour. And, unlike acrylamide, asparagine can be measured cost-effectively. The objectives of this study were to determine the effect of genotype, nitrogen (N), and sulfur (S) fertility on protein concentration, protein quality, dough rheology, and asparagine concentration in winter wheat. The experiment was set up in a 3x2x4 factorial in 2017 and 3x2x5 factorial in 2018. There were 3 levels of N (56, 101 and 146 kg ha-1 as urea), 2 levels of S (0 and 22 kg ha-1 as ammonium sulfate), and 4 levels of genotype (cvs. Everest, Fuller, Jagger, and 2137) in 2017 with an additional genotype (cv. SY Monument) added in 2018. Treatments were arranged in a split-split plot design with four replications each year. Protein composition was evaluated as the percent polymeric protein using size exclusion high performance liquid chromatography. Solvent retention capacity was evaluated using the whole grain SDS-SRC hybrid method. In both years, the ratio of polymeric to monomeric protein was increased by sulfur fertilization, although in 2017 total protein decreased due to dilution. In 2017 asparagine concentration in grain was affected by N, S, genotype, and an N by genotype interaction. Without S, Fuller and Jagger had asparagine concentrations of 20.7 to 21.0 µmol/g and Everest and 2137 had lower asparagine concentrations of 12.8 to 13.8 µmol/g (p<0.05). When S was applied, asparagine concentrations declined to < 3 µmol/g, and genotypes were not different from each other. In 2018 treatment effects were not significant. In 2018, S application increased SDS-SRC from 217% to 308%. Treatment effects on dough rheology were evaluated in the 2018 trial using the farinograph. Sulfur application increased average farinograph stability from 9.2 min to 14.6 min. Farinograph stability was effectively predicted by the whole grain SDS-SRC test (R2=0.78). Sulfur deficiency is increasingly common in agricultural soils due to lack of S fertilization, increasing yields removing more S from the soil, and the Clean Air Act improving the removal of S emissions from industrial sites. Therefore, information from this study will help producers manage sulfur-deficient fields to improve grain quality and food safety while maximizing yield potential.