Genetic Studies of Drought Tolerance Indices of F2 Generations Population in Bread Wheat (Triticum aestivum)


The inheritance mechanism for some drought tolerance indices of F2 generations in bread wheat were studied by using Griffing, Hayman and Jinks – Hayman approach’s. During the growing season of 2012-2013, 5 parents and their 20 F2 crosses were sown on 15 Nov., 2012 at the experimental farm, Agric. Research Station/Koya, Erbil under rainfall incidences. The results revealed that some parents exhibited positive and high general combining ability, whereas, some hybrids showed specific combining ability for the majority of these indices. Mean square values of the Hayman genetic analysis for Yp, Ys and drought tolerance indices showed significant effects in many indices. Gent effect estimations revealed the significant role of additive genetic component ( ) for the inheritance of Ys, MP, GMP, YI, STI and SSI. The relative magnitude of dominant component ( ) was higher as compared to additive component ( ) in most indices. The average degree of dominance ( ) has been >1 for all indices indicates that these indices were controlled by the over-dominance of genes and ample scope for heterosis breeding. The ratio of the symmetry of the frequency of dominant and recessive alleles in all gene location controlling indices (H2/4H1) is less than 0.25 for all indices except TOL. All indices 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 indices, indicating that selection for improvement of these indices would be effective.