Combining Ability of Some Maize Top-Crosses

This investigation was conducted during 2013-2015 to determine the productivity and combining ability of some maize genotypes (74 top-crosses and two check hybrids). Genotypes evaluated at Experimental Farm, Faculty of Agriculture, Al-Azhar University at Assiut Branch. The obtained results revealed that highly significant differences were found among top-crosses and lines as well as, significant or highly significant differences between two testers and the interaction of lines x testers for all studied traits, except ear diameter for testers. Significant desirable GCA effects were found of some inbred lines for all studied traits. Line No.1 had the highest negative GCA effect for number of days to 50% tasseling. So, Line No.1 a good combiner for early tasseling. The highest GCA for grain yield/plant (28.37) was obtained from line No.2 The tester SC-10 was significantly the best general combiner for number of days to 50% tasseling, number of days to 50% silking, ear diameter and number of rows/ear while, the tester TWC-324 was significantly the best general combiner for plant height, ear length, 100-kernel weight and grain yield/plant. Significant desirable SCA effects were found of some top-crosses for all studied traits. Top cross (L8 x SC-10) gave the earliest tasseling (53 days). The highest grain yield /plant (241.37 g) was obtained from Top cross (L31 x TWC-324). The variance due to GCA-L was higher than GCA-T for all studied traits, indicating that most of GCA variance was due to lines. The variance of SCA exceeded that the variance of GCA (average) for all the studied traits, indicating that the non-additive gene action played an important role in the inheritance of all the studied traits. Contribution of lines was higher than testers for all studied traits. So, Lines played the major role in the inheritance of traits.