Variation in traits contributing to improved use of nitrogen in wheat: Implications for genotype by environment interaction

Nitrogen (N) is an essential mineral nutrient for wheat grain yield and quality. Wheat cultivars with improved N-use efficiency (NUE, crop yield per unit availability of N from soil and fertiliser) have the potential to maximise farmers’ revenue and minimise environmental pollution risk. Thus, characterizing wheat cultivars for NUE traits is important for selection of cultivars better adapted to target production environments and for season-specific N fertiliser management. The aims of this study were to examine NUE traits in a set of modern winter wheat cultivars contrasting in phenology and grain-N content, and to assess the likely consequences of genotypic variation in N-related traits for adaptation of cultivars to specific environments. A two-year field experiment was conducted with four widely-grown commercial winter wheat cultivars (Arnold, Aurelius, Bernstein, Emilio) under four N application rates (0, 70, 140, 210 kg N ha⁻¹) at the UFT (Universitäts- und Forschungszentrum Tulln, BOKU) in Austria. Detailed plant and soil data were collected to determine Green leaf area index (GLAI), total shoot dry mass (TDM) and N uptake (TNU) at anthesis and harvest, grain yield (GY), N harvest index (NHI), N remobilisation efficiency (NRE), and NUE.The experimental factors and variation in seasonal weather conditions resulted in a wide range of GY (268 −788 g m⁻²) and TNU (6.6-22.7 g m⁻²). With average values of 80 % for NHI and NRE, all cultivars were very efficient in the use of the accumulated N for producing GY. The observed significant differences in GY were largely due to differences in pre-anthesis N allocation to leaf and stem and post-anthesis DM production and N uptake, as cultivars had similar amounts of TDM and TNU at anthesis. The highest-yielding cultivar Aurelius showed consistently greater N uptake during grain filling. Cultivars also differed significantly in the partitioning of DM and N between leaf and stem in the pre-anthesis phase, with Bernstein showing the highest GLAI and leaf-N content in both experiments. The inter-seasonal variation in environmental conditions strongly influenced the performance and ranking of cultivars with regard to NUE traits and GY. The implications of genotypic variation in traits contributing to improved N use and their importance in better matching cultivar selection to target environments and N fertiliser management are discussed.