Understanding the genetic basis of hybrid performance under different conditions is crucial to design appropriate breeding strategy in variety development. The present study examined the performances of single crosses and the GCA and SCA effects of highland maize inbred lines for grain yield and yield related traits under optimum and low-nitrogen conditions. Eleven inbred lines were crossed using half-diallel mating design, which generated 55 F1 hybrids and tested along with a standard hybrid check. The performances of the hybrids for desirable agronomic traits were evaluated using alpha-lattice design with two replications in 2018 cropping season. Combined analysis of variance across environments showed significant mean squares for all studied traits. Out of the 55 F1s, four hybrids were found consistently high yielders across optimum and low-N environments. Additive gene action was observed more important for GY and yield related traits under optimum management condition than non-additive gene action, which was more important under low-N management condition. Three parental lines manifested desirable GCA effects for GY and some traits under both management conditions. Generally inbred lines exhibited good agronomic performances under both conditions further implying their potential use as inbred line testers in the highland maize breeding program.

Keywords: Diallel, General combining ability, Hybrid performance, Low-nitrogen and Specific combining ability