AbstractAgronomic and quality data from three winter wheat (Triticum aestivum L.) lines, selected from polymorphic breeding population An b7780 grown at Helsinki University (Viikki) were analyzed to determine the effect of nitrate reductase (NR) activity and rate of photosynthesis on grain yield and quality, at Zadoks growth stages GS 13 and GS 47, respectively. This study reveals that in selection for high yield and protein concentration of grains within a winter wheat population one must consider N uptake and translocation to the grains, including long-term capacity for high NR activity and photosynthetic rate. Breeding for NR activity and photosynthetic rate may lead to improved yield, N uptake rate, protein concentration and protein quality of winter wheat.