Experiments to evaluate the performance of 10 bread wheat genotypes with nitrogen deficiency and diagnose the optimal genotype for the appropriate environment commenced in the winter seasons, 2021-2022 and 2022-2023, in three locations of Iraq, i.e., Baghdad, Wasit, and Diwaniyah. All the experiments had a randomized complete block design (RCBD) with split-plot arrangement. Nitrogen levels (0, 50, and 100 kg N ha^-1) occupied the prime plots, with 10 wheat genotypes (T2, T3, S1, S2, S148, IPA99, Adana99, Rasheed, Buhooth-10, and Buhooth-22) allocated to the subplots with three replications in each location. The interaction of wheat genotypes, nitrogen levels, and locations revealed that genotype S2 with 50 kg N ha^-1 at Baghdad showed the highest mean nitrogen use efficiency at 105.00 and 96.00 for 2021-2022 and 2022-2023, respectively. However, these values showed nonsignificant differences from the obtained values of wheat genotypes S148 and the IPA-99 during the second season, in the same location and fertilizer level, i.e., 92.87 and 90.00, respectively. Also, the genotype S2 gave the highest grain yield (6.53 t ha^-1) with N2 fertilizer level in the Baghdad site, not differing significantly from two other wheat genotypes, S148 and IPA99 (6.13 and 5.85 t ha^-1, respectively) in the second season. The presented study authenticated that some wheat genotypes provided good yield under nitrogen stress (50 kg N ha^-1), as there were no significant increases in grain yield when doubling the nitrogen level (100 kg N ha^-1). Therefore, the study suggested these genotypes’ cultivation with nitrogen deficiency to preserve a healthy environment and promote sustainable agriculture.

Keywords: Bread wheat (Triticum aestivum L.), cultivars, nitrogen levels, locations, genotype by environment interaction, combined analysis, biological and grain yield

Key findings: Wheat genotype S2 with 50 kg N ha^-1 in Baghdad for both seasons had the highest nitrogen utilization efficiency of 105.00 and 96.00. Likewise, the genotypes S-148 and IPA-99 yielded 92.87 and 90.00 in the second season at the exact location with the same nitrogen level. In Baghdad, genotype S2 with 100 kg N ha^-1 produced 6.53 t ha^-1 and was at par with S-148 and IPA-99, which yielded 6.13 and 5.85 t ha^-1 in the second season.