Dryland Agricultural Research Institute, Gachsaran, Iran.
Terminal heat and drought are the main constraints for wheat production in the vast and diverse semi-tropical rainfed regions of Iran. High temperature stress during wheat’s reproductive stage is particularly detrimental, reducing both individual kernel weight and kernel number. Identification of adapted genotypes can improve grain yield and its stability under heat stress conditions. Selection to improve grain yield and adaptation to abiotic stress is difficult, making the use of indirect selection for grain yield attractive to plant breeders. Experimental results in diverse environments have indicated remarkable variation for canopy temperature and a significant negative correlation with grain yield, particularly in warmer environments. There is also evidence that adapted wheat genotypes are able to maintain high individual kernel weight despite heat stress. Two recently released wheat cultivars for warm rainfed regions of Iran have shown high grain weight and cooler canopy temperature under different environmental conditions. Therefore, it is concluded that plump grain and cooler canopy temperature are essential traits for the adaptation of wheat genotypes in warm rainfed regions of Iran.