Abstract:
A half diallel cross among seven yellow maize inbred lines was evaluated under low (60 kg N fed-1) and normal (120 kg N fed-1) nitrogen levels for six quantitative characters i.e., plant height, ear length, ear diameter, number of rows ear-1, number of kernels row-1 and grain yield plant-1, to estimate general (GCA) and specific (SCA) combining ability effects and their interactions with nitrogen levels as well as identify the superior inbred lines and crosses. Significant differences were detected between the two nitrogen levels for all the studied traits except ear diameter and number of rows ear-1. Mean squares of crosses and crossesxN interaction were significant for all the studied traits. Both GCA and SCA mean squares were highly significant for all the studied traits under the two nitrogen levels and their combined data. The ratio of GCA/SCA exceeded the unity for plant height, ear diameter, number of rows ear-1 and number of kernels row-1, indicating that these traits were mainly controlled by additive gene action. On the contrary, predominance of non-additive gene action chiefly controlled the expression of ear length and grain yield plant-1 under both and across nitrogen levels. Significant interaction mean squares between GCA and SCA with nitrogen levels were detected for the most studied traits. Three crosses P3xP6, P2xP6 and P4xP7 at low nitrogen level, four crosses P3xP6, P4xP7, P1xP3 and P4xP5 at normal nitrogen level and five crosses P3xP6, P2xP6, P4xP7, P1xP3 and P4xP5 at the combined data were significantly outyielded the check hybrid SC168. The inbred lines P3 and P4 were the best general combiners for ear length, number of rows ear-1, number of kernels row-1 and grain yield plant-1 under both nitrogen levels and their combined data. Six crosses i.e., P2xP6, P3xP6, P4xP5, P4xP7, P1xP3 and P1xP5 were distinguished specific combiners for grain yield plant-1 and most of its components under low and normal nitrogen levels as well as the combined data.
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