Advanced biometrical strategies for genetic analysis and heterosis assessment in maize germplasm

Maize (Zea mays L.) is a cornerstone of global agriculture, contributing significantly to food security and economic stability as one of the world's most important cereal crops. Breeding programs enhancing maize productivity depend on strategically exploiting genetic variation and heterosis. This study employed biometrical approaches to analyze combining ability, heterosis, and heritability in 29 genotypes, including 9 parental lines and 20 F1 hybrids, developed through a Line × Tester mating scheme. Significant genetic variability was observed, with P4 (B73) and P1 (Zheng58) identified as superior combiners for nitrate reductase (NR) activity, glutamine synthetase (GS) activity, and grain yield. Testers P8 (Mo17) and P9 (PH4CV) exhibited strong combining abilities for NR activity, ear length, and grain yield, indicating the importance of parental selection. Additionally, hybrids P1 × P9 (Zheng58 × PH4CV) and P5 × P7 (PH6WC × 178) exhibited strong specific combining ability (SCA) effects, signifying both additive and non-additive gene actions in trait improvement. High mid-parent heterosis (MPH) and better-parent heterosis (BPH) were observed, with MPH ranging from 61.91% to 272.26% and BPH from 32.77% to 216.29% for grain yield, showing the potential for hybrid vigor. High heritability for grain yield, NR activity, and other traits suggests a strong genetic foundation for breeding. These findings highlight the integration of genetic variability, combining ability, and heterosis, optimizing hybrid performance and enhancing parental selection in future breeding programs.