Estimation of The Combining Ability and The Gene Action for Several of Genotypes for Flax (Linum usitatissimum L.)

In this study, eight Flax genotypes ( Linum usitatissimum L.) and their half diallel crosses were used to estimate the combining ability and its general and specific effects for parents. The parents planted their twenty-eight hybrids at the research station of the Field Crops Department of the College of Agriculture - Tikrit University in the 2019-2020 season. In mid-November, the complete random sector design was used with three replications. to study the traits the duration to 50% flowering, plant height, number of vegetative branches, number of plant capsules, number of seeds per capsule, seeds yield by plant and weight 1000 seeds, average leaf weight, biological yield, leaf percentage, seed yield, and harvest index. The results showed by analyzing the second method of Griffing (b1956), the static model, That the percentage between the components of the combining ability general to the specific was greater than the correct one in the traits, duration to 50% flowering, plant height, duration to maturity, number of seeds per capsule, number of capsules per plant, weight of 1000 seeds and average weight of leaves, while the percentage was less than the correct one in the traits of the number of vegetative branches. Plant seed yield, leaf percentage, biological yield, seed yield, harvest index and that the best parents were significantly desirable due to the effect of their general combining ability to mix the parent (Sakha 2) and the traits of the number of vegetative branches, the number of capsules per plant, the seed yield per plant, the average leaf weight, the total seed yield, and the parent (Giza 8) for plant height, number of capsules per plant, average leaf weight, biological yield, and total seed yield and that the highest hybrids were significantly desirable for the effects of the special combining ability in the hybrid (Sakha 2 × Syrian), the trait of the number of capsules per plant, the number of seeds per capsule, the weight of 1000 seeds, the yield of seeds per plant, the total seed yield and the harvest index, The values of the dominant genetic variance were higher than the additional genetic variance in all traits except for plant height, duration to maturity, and number of seeds per plant, indicating the importance of the dominant gene action in controlling these traits. The values of the broad sense heritability were high in traits, duration to 50% flowering, number of capsules by plants, yield of seeds by plants, weight of 1000 seeds, seed yield and harvest index, The average for the traits was plant height, duration to maturity, average leaf weight and biological yield, and a narrow sense heritability was the average for the traits of the duration to 50% flowering, plant height, duration to maturity, number of capsules per plant, weight of 1000 seeds, average leaf weight. Regarding the average of the degree of dominance, it is noted that the duration to 50% flowering, the number of capsules by the plant, the yield of the seeds by the plant, the weight of 1000 seeds, the average leaf weight, the biological yield, the percentage of the leaves, the seed yield and the harvest index, were greater than the correct one, which indicates the existence of suppression segregates with the importance of the Dominant gene action. When estimating the genetic improvement as a percentage of the general average for each traits, it becomes clear that it was low for to most the studied traits except for the number of capsules in the plant. It was average.