Genetic investigation of grain yield and its components in bread wheat genotypes using diallel method

In order to estimate genetic variance components and to determine the gene function, this experiment was conducted using crosses from 12 parents through diallel mating design in bread wheat. A total of 66 F2 hybrids obtained from a one-way diallel cross with their parents in a randomized complete block design (RCBD) were conducted in West Azarbaijan Agricultural Research Station in Saatlu region in three replications during 2013. The results of analysis of variation showed a significant difference between parents and F2 crosses in studied traits. The significance of the mean square of the parents against the crosses indicated a significant heterozygosity for the traits. Considering the significant differences for mean squares of General Combination Analysis (GCA) and Special Combination Analysis (SCA) in plant height, number of spikelet per spike, harvest index and biological yield, both additive and non-additive effects gene effects played a significant role in genetic control of traits. The highest heritability was belong to plant height with 83.7% and the lowest one was belong to harvest index with 54.2%. Narrow sense heritability varied from 16.1 for grain number per spike to 54.2% for plant height. Two parents of Qirmizigul-1 and Qiymatli-2/17 had the highest rank in most traits of yield components and had the highest GCA. In the studied traits, the frequency of dominant and recessive alleles was not in equilibrium in most traits, and dominant alleles were more than recessive ones. According to the graphical analysis of Hayman-Jinks analysis, it can be concluded that for peduncle length, number of seeds per spike, single plant grain yield and biological yield, are controlled by over dominant gene actions, while harvest index was controlled by relative dominant one. Final results of this experiment showed that increasing of grain yield per plant, number of seeds per spike, spikelet number, biological yield, plant height and peduncle length were controlled by recessive allels. Since both additive and non-additive effects are involved in controlling of grain yield, it is possible to assemble additive genes and create an opportunity to gain of dominance variation in a breeding program with suitable selection method, such as periodic selection.