Genotypic variation and stability for nitrogen use efficiency in winter wheat

Wheat (Triticum aestivum L.) products account for a large portion of the total dietary calories and protein consumed globally, thus requiring efficient N management systems for optimal grower profitability and to reduce negative environmental impacts of nontarget fertilization. This investigation sought to evaluate genotypic variation for N use efficiency (NUE), assess yield stability, and validate traits for improvement of crop performance across N rates. Three separate studies were conducted over four growing seasons in the eastern United States that varied in the number of N rates and site-seasons. Study I was conducted using five N rates over three site-seasons, Study II was conducted using three N rates over six site-seasons, and Study III was conducted using two N rates over nine site-seasons. Genotype x N rate interactions were more frequently observed for grain yield when three or more N rates were used in the experimental design. The three studies identified significant genotypic variation for NUE and identified wheat lines that consistently expressed high grain yields over N-site-seasons. Aboveground biomass at physiological maturity was strongly associated with grain yield in Study II when 67 kg N ha(-1) (r = .66, P <= .05) was applied and in Study III when 67 kg N ha(-1) (r = .71, P <= .05), and 134 kg N ha(-1) (r = .89, P < .001) was applied. Findings from this investigation inform soft red winter wheat breeders on diverse sources of breeding materials and target traits to improve NUE.