The influence of different nitrogen treatments on the size distribution of protein fractions in hard and soft wheat

The relative quantity of specific proteins, protein subunits, as well as amount and size-distribution of polymeric proteins in wheat kernels may vary due to environmental conditions. In this study, the effect of different nitrogen treatments on polymeric and monomeric proteins in wheat was determined. Two soft white biscuit wheat cultivars, a cracker wheat and a hard red bread wheat were planted under irrigation in a randomized complete block design with three replications in two successive years at six different nitrogen treatments. SE-HPLC was used to determine the amount of monomeric and polymeric proteins, and various quality characteristics were measured after harvesting. The large and small SDS-extractable polymeric proteins were not influenced by different N levels. There was a strong cultivar influence, where some cultivars had a larger reaction to N treatments than others. The later application (at flag leaf stage) of nitrogen did not increase the protein fractions. The total amount of N given seemed to have a greater influence on the protein fractions than the timing of the fertilizer application. The lowest N treatment consistently gave the lowest flour protein content value. There was a strong correlation between flour protein content and large monomeric proteins.