Abstract

Recognising the importance of developing biofortified maize with enhanced nutritional quality and stable performance across diverse environments is critical for addressing malnutrition and ensuring sustainable food security. This study elucidated the inheritance patterns, genetic parameters, and genotype-environment interactions (GEI) of grain yield, tryptophan, and carotenoid contents. Two maize inbred lines that exhibit contrasting genetic parameters (TZEEIORQ 10 and TZEEI-4) were crossed to produce six generations (P1, P2, F1, F2, BC1P1, and BC1P2) and tested in two locations across two years. Generation mean analysis revealed that additive gene action predominantly controlled these traits, with some influence from dominance and epistasis. The TZEEIORQ 10 plant had superior agronomic and nutritional properties compared to TZEEI-4. Heterosis was observed in the F1 hybrids, with small reductions in the F2 generations due to genetic recombination. Higher trait values were retained in backcrosses, BC1 (F1 × TZEEIORQ 10), promoting additive contributions through genetic inheritance. Pearson correlation analysis showed strong positive associations between grain yield and carotenoid fractions (β-carotene r = 0.83**, β-cryptoxanthin r = 0.78**, zeaxanthin r = 0.85**), and between tryptophan and carotenoids. GEI analysis indicated considerable genetic and environmental effects of 14-16% as genotype-by- environment interactions. The Which-Won-Where analysis identified high-performing, adaptable genotypes. Additive main effects and multiplicative interaction analysis confirmed significant genotypic effects, with genotypic variation explaining 45.2% of yield variation. The predominance of additive genetic effects suggests that recurrent selection and hybridisation can enhance grain yield and nutritional traits, facilitating the development of biofortified maize varieties suited to diverse agroecological conditions.