Exploring Qualitative and Quantitative Genetic Variations of Barley (Hordeum vulgare L.) Genotypes Grown under Heat Stress Conditions
: Heat stress is a major abiotic constraint limiting barley ( Hordeum vulgare L.) productivity in regions experiencing rising temperatures. This study evaluated the genetic variability and morphophysiological as well as yield responses of 50 barley genotypes under control and heat-stressed conditions to identify superior lines for thermotolerance breeding. A completely randomized design (CRD) with replications was used, and data was collected for ten morpho-physiological and yield traits. Analysis of variance (ANOVA) indicated highly significant ( p ≤ 0.001) effects of genotype, treatment, and their interaction on most of the measured traits. Wide phenotypic variation was observed for grain yield (1.62–9.60 g plant − 1 ) and thousand-grain weight (19.18–40.02 g). High genotypic and phenotypic coefficients of variation, heritability, and genetic advance for grain yield plant − 1 , total biomass accumulation plant − 1 , and leaf area plant − 1 indicated strong additive genetic control. Correlation and network analyses showed strong positive associations among plant height, total biomass accumulation plant − 1 , chlorophyll content, leaf area plant − 1 , thousand-grain weight, and grain yield plant − 1 . Heatmap clustering and the multi-trait genotype-ideotype distance index (MGIDI) identified BD7194, BD7188, BD8579, BD9681, and IBON14 as best heat-tolerant genotypes. Principal component analysis (PCA) revealed variation primarily driven by grain yield plant − 1 , leaf area plant − 1 , and number grains spike − 1 . Overall, these findings demonstrate substantial genetic variation for heat tolerance and identify promising genotypes that can be used as valuable resources for developing climate-resilient barley cultivars suited to heating environments.