Performance, Combining Ability and Heterosis of Some New Maize Inbred Lines under Normal and Stress Conditions Using Line × Tester Mating Design.

Eight maize inbred lines were crossed with three testers, which were assessed with their
24 F1 crosses under normal and stressed watering conditions, to estimate their combining
abilities and heterosis during the 2024 season. Maize genotypes included lines and testers varied
highly significantly for all studied traits under both conditions except anthesis silking intervals
(ASI) lacking significance. Thus, the investigated maize genotypes had pronounced variations
for all traits. Crosses varied significantly for days to 50% silking (SD) and 50% tasseling (TD)
only under stress conditions, as well as highly significantly for 100KW, Y/Plant, and STI under
normal and stress conditions. P. vs C. showed a highly significant mean square for all studied
traits under both conditions except for ASI. The parental lines for ASI recorded nearly the same
interval value (2.50 and 2.54) under both conditions, which indicates and provides that these
inbred lines tolerance to drought. The inbred No.52 recorded the highest value for stress
tolerance index (STI) (0.796). The cross I.278×SC.10 showed the highest value for STI (1.310)
compared with all crosses. However, the previous crosses exhibited the highest grain yield
(253.9 and 229.3 g) under normal and stressed conditions. Regarding combining ability, lines
I.278 and No.52 exhibited the most favorable general combining ability (GCA) effects for grain
yield, while hybrids No.52×SC.128, No.45×SC.128, and No.26×SC.128 showed significant and
positive specific combining ability (SCA) effects. These results strongly recommend
I.278×SC.10, and other top-performing crosses, as promising hybrids for stressed environments
due to their superior yield performance and drought tolerance.