Heterosis and Combining Ability Studies in A 5x5 Diallel Crosses of Maize Inbred Lines

The present study was conducted to evaluate the genetic architecture of five diverse maize genotypes using combining ability analyses. General combining ability (GCA) mean squares were non-significant for grain yield and its related components. Specific combining ability (SCA) mean squares were highly significant for grain yield, the number of grains per row and cob girth while non-significant for days to tasseling, days to silking, plant height, cob height and cob length. These studies suggested the preponderance of non-additive type of gene action for grain yield, cob girth and number of grains per row and additive gene action for days to tasseling, days to silking, plant height, cob height and cob length. The genotypes MIL2020-51 and MIL2020-52 were good general combiners for grain yield, grains per row, cob height and plant height. These lines were the poorest general combiner for days to 50% tasseling and days to 50% silking which suggested that these genotypes had sufficient genes for inducing earliness. The crosses MIL2020-51 x MIL2020-54, MIL2020-52 x MIL2020-53, MIL2020-51 x MIL2020-55, MIL2020-53 x MIL2020-55and MIL2020-52 x MIL2020-55 were the best performing combinations for grain yield. These crosses involved good x good and good x poor general combiners. The reciprocal cross combinations MIL2020-55 x MIL2020-53, MIL2020-52 x MIL20220-51, MIL2020-54I x MIL2020-52, MIL2020-55 x MIL2020-51, MIL2020-54 x MIL2020-51and MIL2020-55 x MIL2020-54 showed large positive estimates for grain yield suggesting that cytoplasmic inheritance also had a role in the expression of grain yield. SCA variances were higher than GCA variances for grain yield, plant height, cob height, number of grains per row, cob girth and cob length which highlighted major role of non-additive genes in the inheritance of these traits. Additive gene action was found more important for number of days to 50% tasseling and number of days to 50% silking