Estimation of Genes Effect and Combining Ability of Agronomic Traits in Some Bread Wheat Varieties under Drought Stress

Drought is one of the main dangers for optimum production of wheat. Achieving optimal results in breeding programs require to make informed choices of parents based on general and specific combining ability.In order to study the genetic characteristics, general and specific combining abilities and gene actions under drought stress conditions, a half diallel cross including 9 varieties of wheat was used. Seeds of parents and F2 hybrids were planted based on a randomized complete block design with three replicates in Shahid Bahonar University in autumn of 1392. Parents and F2 progenies were compared in a number of agronomic traits such as plant height,days to maturity,spike length,peduncle length,seed weight,flag leaf area and grain yield. Diallel results based on method 2 of Griffing B model and Hayman _ Jinks showed that general combining ability was significant for seed weight, plant height, days to maturity, peduncle length in statistical level of 1% and for the other traits at 5% statistical level and specific combining ability was significant for seed weight, plant height and grain yield in statistical level of 1% and for the other traits at 5% statistical level.The ratio of mean square of gca to sca was significant for all traits except of grain yield.Therefore, in grain yield most genetic variation is belonged to non-additive genetic variances. The broad and narrow sense heritabilities for the studied traits had ranged from 55 to 74 and from 32 to 61 percent, respectively. The Hayman _ Jinks graphical analysis showed plant height, days to maturity and grain yield controlling by over dominance gene actions however the other traits was controlled by relative dominance gene actions.