Genetic Variability and Heritability of Maize Yield in Diverse Inbred Lines: Implications for Economically Efficient Breeding

Abstract

Effective maize breeding relies on a precise understanding of how genetic factors contribute to phenotypic expression. However, Environmental Variance (EV) often masks true genetic potential, complicating selection and determining the utility of direct selection. Therefore, this study was conducted to investigate genetic parameters in 50 diverse maize inbred lines across 16 agronomic, morphological, and yield traits, with the primary aim of classifying these traits to inform and optimize economically efficient breeding strategies. Analysis of variance confirmed highly significant genetic differences (P < 0.01) for all traits, demonstrating substantial exploitable genetic variability. Genotypic coefficients of variation (GCV) ranged from 1.02% (Days to Dry Husk) to 13.75% (ASI). Anthesis-Silking Interval (ASI) demonstrated exceptional selection potential, exhibiting the highest broad-sense heritability (h²) and genetic advance (GA% = 27.70%) and lowest for Days to Dry Husk and Grain Weight (0.20). This confirms ASI is under strong additive gene control and is suitable for reliable direct phenotypic selection. Genetic advance as percentage of mean (GA%) varied from 0.95% (Days to Dry Husk) to 27.70% (ASI). Key yield components, including Grain Yield Per Plot (h2 = 0.41, GA% = 11.28%) and Cob Weight Per Plant (h2=0.43, GA% = 12.86%), showed moderate heritability and moderate genetic advance, indicating that effective selection is feasible if the high EV is managed. Conversely, phenological traits like Days to Dry Husk and Days to Anthesis exhibited low heritability (0.20–0.23) and minimal genetic advance (0.95–1.31%), suggesting limited improvement via conventional direct selection and recommending heterosis exploitation instead. Economic analysis suggests prioritizing selection for ASI, Cob Weight Per Plant, and Kernel Rows Per Cob to maximize genetic gain. The findings provide a strong basis for genetic improvement, confirming that a successful breeding program must integrate direct selection on additive traits with targeted heterosis breeding for traits controlled by non-additive gene action.