Differences between two grain sorghum genotypes in adaptation to drought stress. I. Crop growth and yield responses

A sorghum F1-hybrid, E57 , with reputed drought resistance was compared with another F1-hybrid, TX- 671, under irrigation and dryland conditions of severe rainfall insufficiency but ample soil water at depth in a deep cracking clay soil. Significant cultivar differences in grain yield occurred under rain-fed but not under irrigated conditions. Differences in yield were associated with different morphological responses to drought stress, with the variety E-57, in comparison with TX-671, having a lower level of floret abortion, the ability to maintain green leaf area longer during grain-filling and probably a higher root to shoot ratio. The implication of these results in relation to adaptation to drought stress is discussed.