Responses of some sunflower genotypes to drought stress using different stress tolerance indices

To determine the genotypes with high yield and tolerance to drought stress and find the best drought stress indices, a field experiment was carried out in a randomized complete block design with three replications. In this experiment six genotypes of sunflower Azargol, Allstar, Record, Mehr, CMS60/52*R82 and CMS19*R256 were evaluated at Islamabad Research Station in 2002-2003. Genotypes were planted in two separate experiments, one with normal irrigation and the other with three irrigations in planting, buding and flowering stages. Results showed that drought stress caused a severe reduction in leaf area index, grain and oil yield, stem diameter and plant height. Under normal irrigation condition the highest grain yield obtained from Mehr and Record with 3908 and 3901 kgha-1, respectively. In drought stress conditions, the highest grain yield obtained from Azargol and Record with 2850 and 2634 kgha-1, respectively. It appeared that stress tolerance index (STI) and geometrical mean (GMP) might be the best indices to evaluate the genotypes for drought stress tolerance