Identification of high-yielding and stable genotypes of barley in the cold climate of Iran using AMMI and GGE biplot models

Breeding strategies aiming at achieving broad adaptation require an initial characterization of genotype-by-environment interaction (GEI) through multi-environment trials (METs). A panel of 17 recently developed barley genotypes, along with a local check cultivar, was evaluated over two cropping seasons (2021-2023) across eight locations within the cold climate zone of Iran: Ardebil, Miandoab, Arak, Hamedan, Mashhad, Jolgeh-Rokh, Tabriz, and Karaj. To assess genotype responses to terminal drought stress, additional targeted evaluations were conducted in Hamedan and Mashhad, which represent the most drought-prone environments in the region. The contribution of GEI to grain yield variation was substantial, accounting for 51.28% of the variation according to the additive main effects and multiplicative interaction (AMMI) model and 17.47% based on combined analysis of variance (ANOVA). Several genotypes were identified as both stable and high-yielding according to the AMMI model and associated stability parameters, including WAAS, WAASY, and AMMI biplot analyses. The GGE biplot analysis indicated that Hamedan and Tabriz were the most representative and discriminative testing environments. The multi-trait stability index (MTS), which integrates drought tolerance indices such as TOL, STI, MP, GMP, YI, and RSI, identified STI as having the highest selection gain (SG) among the evaluated indices. Based on the MTS index, genotype G3 emerged as a promising candidate for drought-prone environments. Furthermore, based on yield performance and specific adaptability across target environments and drought stress conditions, genotypes G3 and G4 were identified as superior entries according to polygon and ideal genotype analyses. These genotypes are therefore strong candidates for further validation and potential varietal release in the cold agroecological zones of Iran, as well as in regions with comparable climatic conditions.