Identification of Heat-Tolerant Wheat Genotypes Through Integrated Physiological, Yield, and Multivariate Statistical Analysis

Terminal heat stress during reproductive and grain filling stages is a major constraint to wheat (Triticum aestivum L.) productivity globally, particularly in emerging wheat ecosystems such as Manipur, Northeast India. This study evaluated the heat tolerance of 12 diverse wheat genotypes under normal and delayed sowing conditions that simulate terminal heat. Integrated physiological parameters (chlorophyll content, canopy temperature depression, relative water content, membrane stability index, chlorophyll fluorescence), yield traits (tillers per plant, spike length, grains per spike, 1000-grain weight, grain yield per plot), and multivariate statistical tools (Principal Component Analysis (PCA), Cluster Analysis, and Multivariate Regression) were used to discriminate heat-tolerant lines. Heat stress significantly reduced physiological efficiency and yield across genotypes; however, genotypes HD 2967, PBW 343, and UP 2338 consistently maintained higher physiological stability and yield under stress. PCA revealed that a combination of canopy cooling, membrane integrity, and chlorophyll retention accounted for 68% of the variation in heat tolerance. Heat Susceptibility Index (HSI) and Stress Tolerance Index (STI) further corroborated the superior performance of these genotypes. The results suggest that integrated physiological and multivariate statistical screening enhances the identification of heat-tolerant wheat, providing vital germplasm for climate-resilient breeding programs in Manipur and similar agro-climatic zones.