Differential Responses of Landrace and Improved Spring Wheat Genotypes to Stress Environments
Drought and heat stress are major environmental factors reducing grain production of rainfed wheat (Triticum aestivum L.) in semiarid regions. The objective of this research was to identify bread wheats with improved adaptation to hot, dry environments. Field studies were conducted to measure effects of terminal drought and heat stress on duration of developmental phases, grain yield, and yield related traits of day-length insensitive spring wheats. Fifteen genotypes, including lines from landraces of southwestern Iran and improved cultivars from Iran and California, were grown in a nonstress and three artificially imposed stress environments at Moreno Valley, CA, in 1986. Genotype ✕ environment interactions were significant for grain yield and its components. Stress susceptibility of each genotype was estimated using a calculated index based on grain yield. Landrace genotypes and improved cultivars that were evaluated exhibited a wide range in stress susceptibility and adaptation to stress environments. Landrace genotypes and cultivars did not vary for mean stress-susceptibility index values. Landrace genotypes generally had lower yield potential than the cultivars. The stress-susceptibility index identified some genotypes that did not have outstanding yield performance per se in stress environments due to low yield potential and others that had high average yield in stress conditions. Stress susceptibility and yield potential were not associated, indicating that they may be independent components which both contribute to adaptation to stress environments. The stress-susceptibility index was negatively correlated with number of grains per head, grain weight, grain yield, and harvest index under stress conditions, indicating selection for these characters in stress environments might result in decreased susceptibility to stress.
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