Assessing Genotype × Environment Interactions for Yield Stability and Grain Quality in Spring Barley Under Contrasting Agro-Ecological Conditions for Sustainable Agriculture

Increasing climate variability is placing growing pressure on cereal production systems, highlighting the need to identify stable and resilient genotypes for sustainable crop production. This study evaluated phenotypic variability, grain yield, yield stability and grain-quality traits in 25 spring barley (Hordeum vulgare subsp. distichon (L.) Körn.) genotypes, including varieties and advanced breeding lines, under contrasting agro-ecological conditions in Romania. Field experiments were conducted over two growing seasons (2024–2025) at Turda and Fundulea using a randomized complete block design with three replications. The evaluated agronomic, phenological, and quality traits included plant height, heading and flowering time, thousand-kernel weight, grain yield, and grain protein and starch contents. The effects of year, location, genotype and their interactions were analyzed, and GGE biplot analysis was used to examine genotype performance and stability across environments. Across the 300 plot-level observations, grain yield ranged from 1631 to 7730 kg ha−1, with an overall mean of 5283 kg ha−1 and a descriptive CV of 21.99%, reflecting overall variability across the dataset rather than experimental error. Year and genotype significantly affected all evaluated traits, while location significantly affected all traits except plant height. For grain yield, protein content, starch content, thousand-kernel weight, heading time, and flowering time, all main effects and interactions were significant (p < 0.001). For plant height, the location effect was not significant, whereas year, genotype, and the interaction terms were significant. Mean grain yield ranged from 4149 kg ha−1 at Fundulea in 2024 to 6364 kg ha−1 at Turda in 2025. Grain yield was strongly negatively correlated with protein content (r = −0.832, p < 0.001) and positively correlated with thousand-kernel weight (r = 0.767, p < 0.001). Ioana had the highest grain yield in three of the four environments and the highest thousand-kernel weight in all four environments, while also showing early heading and flowering in three environments. In the AEC analysis, To 2112-21 showed a more stable yield response across the four tested environments, whereas Ioana was characterized primarily by high yield performance. These findings identify promising barley germplasm for further multi-environment evaluation and breeding for productive, adaptable spring barley under variable growing conditions in central and southeastern Romania.