Introduction
Barley is a key cereal crop known for its broad adaptability to diverse environmental conditions, particularly abiotic stresses such as drought, salinity, and low temperatures. In semi-arid regions, barley cultivars are exposed to drought stress during critical growth stages, which can significantly affect productivity. Given the importance of selecting suitable cultivars for these environments, this study aims to evaluate barley cultivars based on their morphological and phenological traits, and to identify the characteristics most closely associated with grain yield, in order to determine the best-performing cultivars under drought conditions.
Materials and Methods
In this experiment, 17 promising barley genotypes, along with four control genotypes, were evaluated under two conditions: non-stress irrigation and terminal drought stress, during the 2022–2024 growing seasons. The study was conducted using a randomized complete block design with three replications at the Darab Agricultural and Natural Resources Research Station. The multi-trait genotype–ideotype distance index (MGIDI) and multi-trait stability index (MTSI) was used to identify superior genotypes based on grain yield and other measured traits. The evaluated traits included number of days to heading (DHE), number of days to maturity (DMA), plant height (PLH), grain filling period (GFP), grain filling rate (GFR), thousand grain weight (TGW), grain yield (YLD), number of grains per spike (NGS), spike harvest index (SHI), spike fertility index (SFIm), and spike weight (SPW).
Results and Discussion
The combined analysis of variance for the studied traits indicated that the effects of environment, genotype, and genotype × environment interaction were significant for all examined traits. The environment was the primary source of variation for DHE, DMA, GFR, TGW, and YLD, whereas genotypic effects were the main source of variation for PLH, GFP, NGS, SFIm, and SPW. Factor analysis within each environment and across all environments revealed a strong association between YLD and traits such as GFP, GFR, SHI, and SFIm. Indirect selection based on these traits under both non-stress and drought stress conditions may improve grain yield in barley genotypes. Based on the MGIDI index under non-stress conditions (2022–2024), genotypes G16, G2, G20, and G1 outperformed the others, while under drought stress conditions, genotypes G16, G18, G10, and G14 were identified as superior. According to the MTSI index across all environments, genotypes G5, G8, and G3 were among the most stable for the studied traits. Under non-stress conditions, the selection differential was positive for all traits except DHE, with the highest values observed for YLD (12.6), SFIm (8.64), and GFP (8.19), indicating the effectiveness of the MGIDI method in selecting high-yielding genotypes with desirable agronomic traits. In contrast, under drought stress conditions, the selection differential was negative for DHE, DMA, and PLH, while the highest values were recorded for SFIm (13.90), YLD (10.7), and GFR (9.35). This suggests that the method is effective in selecting early-maturing genotypes with high grain yield, grain filling rate, and spike fertility index under drought stress. Across all environments and under both conditions over the two-year study period, the greatest genetic gains were observed for grain yield, grain filling rate, and spike fertility index, indicating successful identification of genotypes with high yield potential, efficient grain filling, and improved spike fertility. 
Conclusion
Overall, the results indicated that the selected genotypes under non-stress conditions (G16, G2, G20, and G1) exhibited a favorable combination of traits, including a long grain filling period, high grain filling rate, high grain yield, a high number of grains per spike, a high spike fertility index, and consequently high spike weight. In contrast, the genotypes selected under drought stress conditions (G16, G8, G10, and G14) were characterized by a long grain filling period, high grain yield, and a high spike fertility index. Therefore, these genotypes can be considered potential candidates for cultivation under both non-stress and terminal drought stress conditions. Notably, genotype G16 was selected under both conditions, indicating its superior performance and adaptability, and it can be introduced as a leading genotype. Furthermore, based on the MTSI index, genotype G3 was identified as one of the most stable genotypes, with grain yield exceeding the overall mean.