Evaluation of some bread wheat genotypes for low nitrogen fertilization using different stress tolerance indices

THIS STUDY was conducted for evaluation of some promising Egyptian cultivars to identify low-N-tolerant wheat genotypes by integrating stress indices (STI, GMP) with GGE-biplot analysis, offering a dual approach for breeding programs. The study was conducted as two field experiments at the experimental farm of El Gemmeiza research station. The two growing seasons 2021/2022 and 2022 / 2023 under four rates of nitrogen fertilizer (60, 120, 179 and 239 kg N / ha.). The experiment was designed in split plot. with three replications. Results showed that, the mean square of genotypes, nitrogen and their interactions showed high significance of all studied traits. Nitrogen stress shortened the heading duration The nitrogen stress caused a shorter duration to heading in the 1^st season by an average of 14.22% and 13.41 % in the 2^nd season and by an average of 8.45% and 7.77% and average of 3.46% and 3.83% under 1^st, 2^nd and 3^rd nitrogen fertilizer rates, respectively, compared with the normal rate (N=75 kg nitrogen) under both conditions, Misr1 and G3 displayed the shortest plants, while Sakha 95 and G1 genotypes exhibited the earliest heading and maturity dates. Under both circumstances, Misr 2 was the best genotype overall in terms of the number of kernels per spike, 1000-kernel weight, and grain yield ton/ha . According to the GGE-biplot, Misr 3, G5, G6, and Giza 171 were the most stable cultivars across all eight environments. The correlation coefficients between grain yield under normal and low nitrogen conditions and stress tolerance indices show that the optimum yield indices in low and normal nitrogen circumstances can include the stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), and harmonic mean (HM).