EFFECT OF NITROGEN-FERTILIZATION ON QUANTITY OF FLOUR PROTEIN-COMPONENTS, DOUGH PROPERTIES, AND BREADMAKING QUALITY OF WHEAT

Three winter wheat varieties with differing breadmaking quality were g rown at two locations in two years at 0 or 3 x 60 kg of nitrogen appli cation. The effect of nitrogen on amount of different components of gl uten proteins was determined by reverse-phase HPLC. A high amount of n itrogen led generally to a significant increase of total protein conte nt. However, this increase was obvious only for the gluten proteins; a lbumins and globulins remained nearly unaffected. The effect of increa sed protein content on gliadin to glutenin (gli-glu) ratio was inconsi stent. While increased protein content increased the gli-glu ratio in the variety Capo, the opposite was true for the variety Renan. Gli-glu ratio of the variety Lindos showed no discernible tendency. As total protein content increased, the ratio of low molecular weight (LMW) to high molecular weight (HMW) glutenins decreased consistently, i.e., in all varieties, in both years and locations. Change of LMW to HMW rati o showed a significant negative correlation to sedimentation value and bread volume. There was no consistent change in the ratio between x- and y-type HMW subunits due to fertilization, as could be shown by den sitometric measurements on SDS-PAGE gels. This ratio appeared to be de pendent on the genotype and has decreased with decreasing quality. The amount of x-type subunits correlated closely with sedimentation value and bread volume. These results suggest that ratio of HMW glutenins, especially x-type subunits, to total protein content could be the best early detectable parameter with high predictive value for breadmaking quality.