Poor soil fertility is among the major abiotic stresses affecting maize productivity in Ethiopia. The objectives of this study were to assess hybrid performance and estimate combining ability of elite QPM inbred lines under optimum and low-Nitrogen (Low-N) stress conditions. One hundred and six testcross hybrids generated from line x tester crosses were evaluated together with four checks under optimum and low-N stress conditions at four locations in Ethiopia during the 2015 cropping season using a 5 x 22 alpha lattice design. Combined analysis of variance showed highly significant variations among the genotypes for grain yield and most other agronomic traits under optimum, low-N stress and across environments. Across environments, 10 and 79% of the new QPM hybrids had superior performance over the commercial QPM check (ZS261) and non-QPM check (SC627), respectively. Both general (GCA) and specific (SCA) combining ability mean squares were significant for grain yield and most other agronomic traits under each management and across environments, indicating the importance of both additive and non-additive genetic effects in the inheritance of these traits. However, the proportion of additive gene action was higher than that of non-additive for grain yield and other traits under optimum management and across environments. Combined analysis across environments showed that L3, L6, L8, 16 and L18 were good general combiners for grain yield. L4 exhibited good GCA for reduced days to anthesis and silking, and plant and ear heights. QPM inbred lines and high yielding hybrids identified in this study could be used as potential source germplasm for breeding low soil fertility tolerant varieties.
