Influences of cultivar and nitrogen application on protein concentration and composition, and amount and size‐distribution of different protein components, were investigated in 10 spring wheat cultivars (Triticum aestivum L.) with widely varying gluten strength, grown under four nitrogen fertilizer conditions. The results showed that cultivar differences in gluten strength were determined by storage protein composition, differences in total amount of HMW glutenin subunits, the glutenin‐to‐gliadin ratio, and the relationship between SDS‐soluble and SDS‐insoluble protein polymers. Negative correlations were found between protein parameters related to gluten strength and bread volume. No cultivar stability for gluten strength in relation to differences in nitrogen application was found. Thus, the gluten strength was influenced by the nitrogen application in all the investigated cultivars. Increased nitrogen supply correlated significantly to an increase in all protein components containing gliadins and glutenins, but not to those containing albumins and globulins. The increase in protein components containing gliadins and glutenins correlated significantly with an increase in protein concentration and bread volume.

The influence of nitrogen (N) fertilizer application rate (0 vs. 70 vs. 140 kg N ha–1) and timing (early = at sowing vs. late = at sowing and before heading) on the amount of protein groups, amount and size distribution of mono‐ and polymeric proteins, and gluten strength was investigated in one set of wheat cultivars (Triticum aestivum L.). Due to their genetic background, the cultivars had different protein concentrations and gluten strengths. Despite this, all of them reacted similarly on rate and timing of nitrogen application. The rate of nitrogen fertilizer increased the variation in protein concentration, gluten strength, and also the variation in most of the investigated protein components. Higher nitrogen fertilizer rate increased protein concentration, decreased gluten strength, and increased the total amount of glutenins and gliadins as well as the amounts of most mono‐ and polymeric proteins. Timing of fertilizer did not influence protein concentration. The gluten strength and the relations of proteins were changed by the timing of fertilizer. Early nitrogen feritilizer applications led to higher gluten strength and a higher percentage of total unextractable polymeric protein in the total polymeric protein and large unextractable polymeric protein in the total large polymeric protein, compared to late nitrogen fertilizer applications.

The amount and size distribution of polymeric protein, environmentally influenced by temperature and nitrogen timing, is an important factor determining gluten strength in wheat. Differences in mature wheat might be explained by alterations in accumulation and build-up of proteins in the developing wheat grain. One cultivar was grown to maturity in a greenhouse using two temperatures and four nitrogen regimes. Plants were harvested during grain development and protein compositions were determined. Proteins were accumulated and built up similarly independent of temperature and nitrogen regime. Temperature influenced the protein concentration significantly, for all protein types throughout the grain development period and at maturity. The time for increase in amount of polymeric proteins differed with temperature if time was measured as days after anthesis, but not if time was measured as degree-days. Different temperature regimes did not generally result in changes in amount and size distribution of polymeric protein. The combination of lower temperature, different nitrogen regimes and one of the cultivations led to changes in the amount and size distribution of polymeric protein in mature grains. These differences were due to a change in amount of SDS-extractable polymeric and large monomeric proteins during grain development, indicating influences on disulphide bond formation.

SU MMARYInfluences of cultivar and environment, i.e. cultivation year and fertilizer rate, on amount of protein groups and amount and size distribution of mono-and polymeric proteins, were investigated in four sets of wheat (Triticum aestivum L.). The cultivars were chosen in order to obtain a high range of variation in protein concentration and gluten strength. Environmental influences on protein concentration and gluten strength were investigated, as well as relations between variation in protein concentration and gluten strength and variation in protein groups and amount and size distribution of mono-and polymeric proteins.The results showed that cultivar and environmental influences giving rise to variation in protein concentration also gave rise to variation in most of the investigated protein components. Protein concentration was significantly positively correlated to the total amounts of glutenins and gliadins and amounts of most mono-and polymeric proteins. However, the correlation with the amount of gliadins and sodium dodecyl sulphate (SDS)-soluble mono-and polymeric proteins were often higher than the correlation to the glutenins and the SDS-insoluble mono-and polymeric proteins. Cultivar influences giving rise to variation in gluten strength were found to influence the relation between SDSsoluble and -insoluble polymeric proteins, leading to a significant positive correlation between the gluten strength and the percentage of total unextractable polymeric protein (TUPP) in the total polymeric protein and large unextractable polymeric protein (LUPP) in the total large polymeric protein. Environmental variation in gluten strength was found to be significantly positively correlated to SDS-insoluble proteins and negatively correlated to SDS-soluble proteins. This also led to a significant positive correlation with the percentage of LUPP and/or TUPP.

Length of GMP, especially in relation to length until maturity, governs gluten strength (%UPP) and grain protein concentration (TOTE). Length of GMP is determined by cultivar, temperature during GMP and late nitrogen availability.