Twenty six yellow maize in-bred lines were topcrossed with three testers, i.e. inbred line Gm-1002, inbred line Gm-1021 and SC-155 at Mallawy Agric. Res. Station to produce 78 topcrosses. The crosses were evaluated at two locations, Gemmeiza (Gm) and Mallawy (Mall) Agric. Res. Stations in 2005 season.. In 2006 season two experiments were carried out at Gemmeiza and Mallawy Agric. Res. Station to evaluate 52 single crosses, 26 three way crosses (TWC) and three check hybrids, namely; SC-155, SC Pioneer-3084 and TWC-352 for days to 50% silking, ear length, no. of rows/ear, no. of kernels/row, 100-kernel weight and grain yield/plot . Combined analysis over the two locations revealed that the mean squares due to crosses, lines, testers and line x tester were significant or highly significant for the studied traits, except testers and line x tester for no. of rows/ear. The interactions of crosses, lines and testers x location were significant or highly significant for the stud-ied traits, except the crosses x location for no. of rows/ear, lines x location for grain yield (Kg/plot) and tester x location for no. of rows/ear and 100-kernel weight. Mean squares due to lines x testers x location interac-tion were highly significant for ear length and no. of kernels/row.
The combined data showed that variance magnitude due to σ2 GCA-L was higher than σ2 GCA-T for all studied traits, except grain yield (Kg/plot), indicating that most of the total GCA vari-ance was due to lines. The ratio σ2A/σ2D was less than unity for no. of kernels/row and grain yield/plot, indicating that the dominance gene action played an important role in the inheritance of these traits. On the other side, the ratio σ2A/σ2D was more than unity for days to 50% silking, ear length and 100-kernel weight.
For grain yield per plot, the combined data revealed that six single crosses (L-13, 9, 14 and L-1 x Gm-1021) and (L-8 and L-9 x Gm-1002) outyielded the best check hybrid SC-3084 by 23.47, 21.64, 19.75, 14.50, 13.66 and 9.45%, respectively. The best 3-way crosses were L-1, 20, 3, 7, 22 and L-25 x SC-155. These 3-way crosses out yielded the check hybrid TWC-352 by 43.1036.19, 34.05, 32.14, 28.57 and 28.33%, respectively. The best GCA effects were inbred lines no. 1, 10, 13, 14 and 16 for days to 50% silking; lines no. 1, 3, 7and 11for ear length; lines no.8, 10, 14, 17, 20 and 24 for no. of rows/ear; lines no.7 and 23 For no. of kernels/row; lines no. 6, 7, 11 and 12 For 100-kernel weight. With respect to grain yield/plot, seven inbred lines (no.1, 9, 3, 7, 8, 20 and 13) over locations had positive and significant GCA effects.
The best SCA effects were 4, 5, 1, 4 and 1 topcrosses for earli-ness, ear length, no. of rows per ear, no. of kernels per row and 100 kernel weight Regarding grain yield/plot based on the combined data, the highest SCA estimates were detected from the topcrosses (line-13 x Gm-1021), (line-14 x Gm-1021), (line-8 x Gm-1002), (line-15 x Gm-1002), (line-25 x SC-155), (line-19 x Gm-1021), (line-1 x SC-155), (line-20 x SC-155) and (line-21 x Gm-1002).