Diallel Analysis for the Estimation of the Genetic Parameters of Grain Yield and Grain Yield Components in Bread Wheat

Diallel analysis was used to estimate the combining ability, gene action, gene number, heritabilties and other genetic parameters of a set of wheat genotypes. For this purpose, nine parents and their 36 crosses were evaluated for 9 traits in a randomized complete block design with three replications in 1996. The analysis of variance revealed significant differences among all genotypes for all traits. Estimates of general and specific combining ability mean squares based on Griffing’s Method 2 indicated the importance of additive and non additive effects in the expression of all traits. Alvand and Roshan cultivars for grain yield per plant, Alvand for grain number per main spike and main spike weight, and Alvand and Alamoot for 1000 grain weight were the best combiners, thus use of them is beneficial for these traits. Based on the estimates of average degree of dominance and results of graphical analysis, the gene action for grain number and spikeletes per main spike were partial dominance, while for grain yield per plant, biological yield, plant height, harvest index and 1000 grain weight, overdominance gene actions were observed. Moreover, genotypic correlation coefficients of grain yield per plant with grain number per main spike, 1000 grain weight, grain weight per main spike and main spike weight were positive and significant.