Estimation of General and Specific Combining Ability Effects for Quality Protein Maize Inbred Lines

Abstract

Background: Maize (Zea mays L.) plays a critical role in meeting high food demand. It is globally one of the most widely adapted and cultivated crops. Hybrid development from fixed inbred lines is one of the strategies for the improvement of maize production. The national average maize yield in Ethiopia is low and thus, selection of promising germplasm and knowledge of combining ability are prerequisites to developing high yielding maize varieties. Forty-two Quality Protein Maize (QPM) crosses (21 inbred lines each crossed with two testers) along with three popular standard hybrids were evaluated in two replications using alpha lattice during the 2017 cropping season at Ambo, Arsi-Negele, and Kulumsa. The objectives of this study were to identify lines with high GCA and estimate the SCA of crosses for grain yield, and other agronomic and morphological characters.
 Results: Significant difference among crosses was observed for 19 traits at Ambo, 14 traits at Arsi-Negele, and 19 traits at Kulumsa in the hybrid trial. Regarding the GCA effect, L8 had a significant difference to the positive side with the highest magnitude of GCA effect at three locations (3.40, 2.03, and 1.88 GCA effect values at Arsi-Negele, Ambo, and Kulumsa, respectively) which is followed by L7 for GY. All crosses did not show a significant SCA effect for GY in both directions at Ambo and Arsi-Negele but at Kulumsa, five crosses: L2xT1(1.89), L13xT2(1.88), L7xT1(1.86), L4xT2(1.49) and L19xT1(1.41) showed significant difference. In the combined analysis for six traits, Additive gene action was more important which was manifested by a higher sum square contribution of DS (79.6) EPP (79.3%), EL (80.0%), KPR (80.1%), ED (78.5%) and TSW (79.1%).
 Conclusion: Based on mean grain yield, and combining ability, L8xT2, L7xT1, L8xT1, L19xT1, L6xT2, and L18xT1 are promising crosses that could be forwarded for further use in maize breeding programs for further works.

Combining Ability and Heterosis of QPM Hybrids for Yield, Qualitative and Quantitative Traits under Heat stress in Different Environments

“…The variability for selection and the expected genetic advance is in the population of singe cross is largest. The whole of the additive, dominance and epistatic components of genetic variation is available for exploitation in single crosses [18,19]. Combining ability investigations of parental generations need to be conducted under appropriately stressed selection environments for the successful selection of suitable parents that can be used in hybridization programs [20].…”

“…Successful estimation of combining abilities involves various steps such as parental selection for crossing, performing crosses using a definite mating design, evaluation and data interpretation. The study of the effects of combining ability, both general combining ability (GCA) and specific combining ability (SCA), are important indicators of potential value for assessing inbred lines in hybrid combinations as a step to develop hybrid varieties in maize [19]. Heterosis and combining ability are the prerequisites for formulating hybrid breeding programme.…”