GENE ACTION OF YIELD AND ITS COMPONENTS OF F2 GENERATIONS POPULATION IN BREAD WHEAT UNDER RAINFALL CONDITIONS

Abstract

A full diallel crosses among five bread wheat genotypes were made during the growing season 2009-2010 . Grains of 20 F1s and their five parents was cultivated during the growing season 2010-2011. During the growing season, 2012-2013, the 5 parents and their 20 F2 crosses was planted on 15 Nov., 2012 at the experimental farm, Agriculture Research Station/Koya, Erbil under rainfall conditions by using Randomized Complete Block Design with three replications in order to analysis genetic control of grain yield and yield components by using Griffing, Hayman and Jinks – Hayman approach’s. The results basis on the performance and combining ability revealed that two parents proved as a best general combiner which can be used in hybridization program for obtaining desirable combinations and two crosses had a best specific combiner in desirable direction for most traits. Additive genetic component (a) were important in the inheritance of all traits except no. of grains/spike and harvest index, in opposite non-additive component (b) were significant of plant height, 1000-grain weight, biomass yield/plant and grain yield/plant. Additive genetic component ( ) was smaller in magnitude than both components of dominance ( and ) for all traits. The average degree of dominance (H1/D) ½ being greater than unity indicated involvement of over-dominance for phenotypic expression of all traits. The ratio of the symmetry of the frequency of dominant and recessive alleles in all gene location controlling traits (H2/4H1) is less than 0.25 for all traits except days to flowering, plant height, no. of spikes/plant and harvest index. Five traits have shown above unity value for the proportion of dominant and recessive genes among the parents (KD/KR). The narrow sense heritability Hn.s. was high for all traits except days to flowering, plant height and no. of spikes/plant, indicating that selection for improvement of these traits would be effective in early generation