Quantitative Genetic Expression, Yield Architecture, and Heterotic Responses in Top-Cross Hybrids from Quality Protein Maize (IPB Var. 6) and Visayan White Corn (Zea mays L.)

Hybrid vigor remains a cornerstone of maize improvement, particularly in nutritionally enhanced germplasm such as quality protein maize (QPM). This study evaluated quantitative genetic expression, yield architecture, and heterotic responses in top-cross hybrids derived from QPM (IPB Var. 6) and Visayan white corn. Significant genotypic variation was detected among hybrids for grain yield and its component traits, indicating substantial genetic diversity and the contribution of non-additive gene action. Several hybrids expressed positive mid-parent heterosis and better-parent heterosis for yield, demonstrating superior performance over parental lines. Yield advantage was largely associated with improvements in ear length, kernel number, and kernel weight, suggesting coordinated trait expression underlying heterosis. These findings highlight the breeding potential of QPM × landrace top-cross hybrids and reinforce the importance of heterosis exploitation for developing high-yielding, nutritionally improved maize cultivars.