Genetic Evaluation of Different Characteristics of Bread Wheat (Triticum aestivum) in Cyclic Drought Stress Condition

Extensive and deep root system play important role in wheat drought tolerance and yield in water deficient condition. Nevertheless، a little is known about root structure genetic. In this research، a half diallel mating design was generated from crosses between eight bread wheat cultivars to study the genetic of root system. Parents and F1 progenies were planted in cyclic stress condition in a randomized complete block design with four replications and root length، root weight، root number، shoot weight، root to shoot ratio، grain yield، plant height and peduncle height were measured. Results showed that additive and dominant effects were significant for all traits. However، additive-dominant model was not adequate for root number. Non-additive variation was more important in genotypic disparity of root length and root to shoot ratio. Consequently، bulk، single seed descent and double-haploid methods are recommended in breeding program for these traits. Additive variation had imperative effect on genotypic variation of root weight and plant height. Thus، despite of mentioned breeding methods، pedigree and back-cross are recommended for these traits. Cultivar Roushan had an appropriate root system and high general combining ability for the root system traits. Accordingly، in breeding programs for developing root system، Roushan is recommended as one of the mating parents.