Heterosis and combining ability analysis of quality protein maize (Zea mays L.) inbred lines adapted to mid-altitude sub-humid agro-ecology of Ethiopia

Generation of information on heterosis and combining abilities of newly developed maize inbred lines is necessary for a successful hybrid and synthetic maize varieties development. Accordingly, this study was conducted to estimate the combining ability of QPM inbred lines for grain yield and yield related traits and to determine the magnitudes of standard heterosis for grain yield and yield related traits in line × tester QPM hybrids. Fifty test crosses together with two standard checks were evaluated using alpha lattice design with three replications at three mid-altitude sub humid trial sites (Bako, Hawassa and Jimma) in Ethiopia during 2016 main cropping season. Combined analysis of variance showed highly significant differences among the three locations for all the studied traits indicating the presence of considerable variation among locations for genotype performance. The interaction between sites and genotypes were highly significant and significant (P<0.05) for grain yield and ear height, indicating that the performances of the genotypes and crosses were not consistent for these traits. The significance of both general combining ability (GCA) and specific combining ability (SCA) mean square for some traits indicates the role of additive and non-additive gene action in the inheritance of the traits. However, for all the traits, the contribution of GCA variance was greater than the contribution of SCA variance, revealing the predominance of additive gene action in the inheritance of all the traits studied. L1 and L3 had significant positive GCA effects and are considered as good combiners for grain yield. In addition, L1 and L9 were good combiners for earliness. In this study, none of the crosses showed positive and significant standard heterosis for grain yield. Key words: General combining ability, grain yield, specific combining ability, standard heterosis.