A field experiment was conducted to estimate combining ability and to identify direction and magnitude of standard heterosis in mid-altitude maize test crosses for grain yield and yield related traits. Eighteen inbred lines and four single cross testers were crossed in line x tester mating design during the 2014 main cropping season. The resulting 72 F1 crosses and three standard checks (BH543, BH546 and BH547) were evaluated in 5x15 alpha-lattice (0, 1) design with two replications in 2015 main cropping seasonat Haro Sabu Agricultural Research Center. The analysis of variance indicated highly significant (p<0.01) genotypic differences for all traits with the exception of shelling percentage, stand count at harvesting and common leaf rust. General combining (GCA) mean square due to lines and testers were significant for all traits except tester GCA mean square for harvesting index, anthesis silking interval, days to anthesis, days to silking and days to maturity. The mean square of specific combining ability (SCA) effect of the crosses revealed significant difference for all traits except for number of kernels per row, plant height, anthesis silking interval, days to silking, gray leaf spot and tarcicum leaf blight. Significant GCA and SCA effects were indicative of the importance of both additive and non-additive gene actions. The present study identified elite inbred lines and testers for grain yield and yield related traits and high yielding test crosses possessing positive and significant standard heterosis over the best check hybrid (BH547). These crosses could be used in maize breeding program after further confirmation of the result through evaluation over years and locations.

Keywords: Additive, Combining ability, Heterosis, Maize, Non-additive