Dissecting Heterotic Patterns and Combining Ability for Grain Yield and Nutritional Composition in Extra‐Early Quality Protein Maize Hybrids

ABSTRACT Addressing food insecurity and malnutrition in sub‐Saharan Africa requires the development of nutritionally enriched and high‐yielding maize hybrids tailored to rainfed agro‐ecologies. This study aimed to dissect the effects of heterosis and combining ability on grain yield and nutritional traits in extra‐early white Quality Protein Maize (QPM) hybrids. A total of 45 hybrids, generated from 10 inbred lines using a partial‐diallel mating design, were evaluated alongside two commercial checks under rainfed conditions in Nigeria during 2023 and 2024. Combined ANOVA revealed highly significant ( p < 0.01) genotypic and environmental effects across all traits, indicating contributions from additive and nonadditive gene actions. GCA/SCA ratios exceeding 1.0 for grain yield (1.86), lysine (1.61), tryptophan (1.60), and quality index (1.62) underscored the predominance of additive genetic effects in trait inheritance. Inbreds TZEEQI 239 and TZEEQI 3 exhibited strong general combining ability for grain yield and nutritional traits, respectively. Crosses such as TZEEQI 3 × TZEEQI 17 and TZEEQI 49 × TZEEQI 62 demonstrated significant specific combining ability for yield, lysine, and carbohydrate content, indicating favourable nonadditive interactions. Standard heterosis estimates indicated a yield advantage of up to 22.1% over commercial checks, accompanied by significant improvements in lysine content, ash percentage, and carbohydrate concentration. Protein quality improvement was validated through biochemical profiling, and the expression of heterosis for tryptophan and crude protein exhibited notable variation among hybrids. The integration of GCA, SCA, and heterosis analyses provides a robust genetic framework for developing superior QPM hybrids. These findings support the advancement of biofortified maize germplasm with enhanced yield and nutritional traits to combat malnutrition and improve food security in sub‐Saharan Africa.