Multi-trait Physio-biochemical Characterization of Contrasting Emmer Wheat (Triticum dicoccon Schrank) Germplasm under Controlled Post-anthesis Heat Stress

Emmer wheat ( Triticum dicoccum Schrank ) is a valuable genetic resource for improving nutritional and climate resilience traits in modern wheat. Fifteen dicoccum wheat genotypes, selected from multi-environment trials during Rabi 2021–22 and 2022–23 at Pune and Delhi based on grain yield HSI, including ten heat-tolerant, five heat-susceptible accessions, and five checks, were studied under control (24/14°C) and heat-stress (32/22°C) conditions at grain filling. Two-way ANOVA revealed highly significant effects of genotype, treatment, and their interaction for most of the traits. Heat stress consistently reduced RWC, MSI, CCI, and Fv/Fm, while SOD, proline, and MDA increased significantly. Under heat stress, SOD activity displayed significantly positive association with membrane stability index (r = 0.741) and relative water content (r = 0.697) and negatively with MDA (r = − 0.624), suggesting reduced oxidative and membrane damage co-occurred with better membrane stability and water content. Principal component analysis explained 63.3% of total variation, with PC1 (48.5%) and PC2 (14.8%) primarily driven by MDA and CCI, respectively. A multi-trait matrix scoring approach categorized genotypes into four tolerance classes, identifying G3, G4, G5, G6, G7, G9, and G10 as moderately heat-tolerant, exhibiting superior membrane integrity, water status, and antioxidant capacity under stress. Integration of HSI-based, physio-biochemical, and field-based classifications consistently identified G10 as heat-tolerant, while G3, G4, G5, G6, G7, and G9 were classified as moderately tolerant. The consistent performance across complementary approaches highlights these dicoccum wheat genotypes as promising and stable sources of heat tolerance for bread wheat improvement.