Can nitrogen fertilization be used to modulate yield, protein content and bread-making quality in Uruguayan wheat?

Genotype and environment jointly determine yield and bread-making quality of bread wheat, being possible modulators for these characters. Eleven cultivars were grown at three different nitrogen regimes combining quantity and timing of nitrogen availability for two years; yield, grain protein concentration and Alveograph parameters were determined. Amount and size distribution of proteins were measured using Size Exclusion-High Performance Liquid Chromatography. The results showed year to be the most important determinant of percentage of unextractable polymeric protein in total polymeric protein (%UPP) and yield, while nitrogen regime determined grain protein concentration, the total amount of SDS-extractable and -unextractable proteins, Alveograph W and L. High nitrogen regime generated three types of responses among the cultivars; i) an increase of yield and grain protein concentration, ii) an increase in grain protein concentration but a reduction in %UPP, and iii) an increase in %UPP. For group ii, a low nitrogen regime at early stages but high at later stages was preferential, while for other groups, a high nitrogen regime during the whole season was the most beneficial. This study showed that it is possible to modulate yield and quality in bread wheat by the nitrogen regime, although an understanding of genotype-environmental relationships is necessary.