Reduction in Morphological and Physiological Traits in Advanced Lines of Wheat (Triticum aestivum L.) under Normal and Lag Phase Heat Stress Settings

Wheat is the staple food of many countries around the globe and approximately over three billion people depend on wheat for their daily calorie requirements. In several wheat-producing countries, wheat productivity has declined due to several biotic and abiotic stresses, largely due to heat and drought. The present study was designed to assess different morphological and physiological parameters in advanced lines of bread wheat under heat stress at the lag phase. Under heat stress conditions, the reduction in lag phase (19.7%) and relative water content (35.5%) was high in the wheat cultivar Subhani-21. Least decline in tiller plant-1 (16.5 %) and plant height (10.1 %) were perceived in advanced line HYT: 100-74 though the decrease in flag leaf area was 7.9 % in V: 20337. The smaller reduction in normalized vegetation index (29.32%) and chlorophyll content (10.62%) was detected in HYT: 100-47, indicating their stay-green trait while low canopy temperature values in heat stress as in HYT: 100-47 (-13.91%) and HYT: 100-74 (-12.9%) indicating their cooler canopies. The lowest value for % yield under stress conditions was observed in HYT: 100-47 (9.35%), followed by HYT: 100-76 (10.86%), HYT: 100-74 (11.33 %), and V: 21448 (14.19%) demonstrating their tolerance to heat stress. Canopy temperature was negatively correlated with all traits in the two states studied. These lines satisfy the standards of novelty, high yield, and heat stress tolerance. Therefore, these advanced lines could be valued and registered to combat heat stress in the country and sustain national food security.