Evaluation of Combining Ability for Some New Yellow Maize Inbred Lines Using Line X Tester Model

This investigation was carried out to study the combining ability effects of 13 parents of maize (10 inbred lines and 3 testers) crossed in line x tester scheme for earliness and yield characteristics. The trial included the 13 parents, 30 top crosses, along with the check hybrids SC 168. The experiment was conducted at two planting dates on 24 May and 14 June 2021 at the Agric. Res. and Experimental Station of the Fac. of Agric., Moshtohor Benha University. The experimental design was randomized complete blocks with three replications. Mean squares due to crosses (C) inbred lines (L), testers (T) and line x tester (LxT) were significant for most studied traits of both sowing dates as well as for the combined analysis. Significance of interaction variance for C, L, T and LxT with sowing dates for the most studied traits was detected.  δ²_SCA played the major role in determining the inheritance of all traits, revealing that the largest part of the total genetic variability associated with these traits was a result of non- additive gene action. The magnitude of the interaction of δ² SCA x sowing date (SD) was generally higher than for δ² GCA x SD. This finding indicates that non-additive type of gene action is more affected by SD than additive and additive x additive types of gene action. The cross L3xT10 was the earlier hybrid since it expressed the lowest values for days to 50% pollen shed (59.58), days to 50% silking (60.5) and days to maturity (91.33). The top crosses   L4xT2, and L7xT1 in early sowing date,   L1xT1, L2xT1, L3xT1, L2xT2, , L1xT3, , L2xT2, , L3xT1, , L3xT2, , L3xT3, , L5xT1, , L5xT2, , L6xT1, L6xT3, L7xT1, L8xT1, L9xT3 and L10xT2 in late sowing date and  L3xT1, L4xT2, L7xT1, and L10xT2  in the combined across sowing date differed significantly from the check SC 168.