Assessing genetic variability in maize inbred lines and hybrids for enhanced agronomic performance under high density planting conditions

Planting density plays an important role in enhancing maize productivity, but tolerance to high-density planting remains limited in several commercial hybrids. Therefore, developing hybrids with high-density tolerance is essential to meet global population increase and climate challenges. This study aimed to assess the combining abilities of newly developed maize lines, identify promising hybrids and investigate gene action controlling key traits under low and high-density planting conditions. Seven maize inbred lines were crossed using a half-diallel mating design to develop 21 F1 hybrids, which were evaluated alongside a commercial hybrid (SC-10) over 2 seasons at low (57143 plants/ha) and high (95238 plants/ha) planting densities. Results showed significant differences in traits due to planting density and hybrid type. Highdensity reduced ear length, kernel number, ear diameter and kernel weight by 11.7, 18.2, 6.3 and 13.17 respectively compared to low-density. Otherwise, it increased plant height, days to silking and grain yield per ha by 11.2, 3.7 and 16.0% respectively, compared to low-density. Lines L1, L2, L5 and L6 exhibited strong general combining ability for improving grain yield under high-density conditions, while L1 and L3 were identified as good combiners for early maturity. Hybrids L2 × L6, L3 × L5, L4 × L7 and L6 × L7 demonstrated significant specific combining ability for increasing maize productivity under high-density. Additionally, L3 × L5 and SC-10, showed high tolerance to density stress. These hybrids are recommended for further testing for potential commercial cultivation, offering valuable insights for developing maize hybrids that adapted under dense planting and contribute to sustainable agriculture.