Evaluation of Australian wheat genotypes for response to variable nitrogen application

Aims The key aim was to assess the genetic variation for nitrogen (N) response and stability in spring wheat germplasm to determine the scope for improvement of nitrogen use efficiency (NUE) under water-limited, low yielding conditions. A further aim was to evaluate NUE stability and NUE-protein yield (PY) as suitable NUE-related traits for selection. Methods The traits measured included grain yield (GY, kg ha −1 ) and NUE (kg GY kg −1 N) under varying N applications at all sites, and NUE for protein yield (NUE-PY), harvest index and plant height at some sites. In addition, two of the trials used two seeding rates to provide an assessment of the impact of plant density on NUE. Results Genetic variation was significant for all traits studied. Grain yield was affected by both genotype (G) and N rate and the interaction between the two. Interestingly, harvest index and height showed no direct response to varying N applications. However, for these traits, there was a significant G effect and N response (G × N interaction). Conclusions Increasing N inputs led to variable responses for GY at different sites. Importantly, genetic variation in N response was detected. The information and screening techniques will enable plant breeders to select wheat genotypes that show a consistent response to high N. There is clear scope to improve NUE in spring wheat grown in low yielding environments.