Genetic Potential of New Maize Inbred Lines in Single-Cross Hybrid Combinations under Low-Nitrogen Stress and Optimal Conditions

Maize (Zea mays L.) productivity in sub-Saharan Africa (SSA) remains low, despite breeding efforts spanning across decades. Currently, three-way cross hybrids (TWCH) dominate SSA; however, there is the potential to increase yields by using single-cross hybrids. In this study, five new and four elite CIMMYT lines were inter-mated in a half diallel mating scheme to estimate the combining ability of the lines and to determine the stability of their corresponding 36 single-cross hybrids for grain yield under low-nitrogen stress and optimum growing conditions in Zimbabwe and Zambia. The results revealed that the new inbred line CL121290 showed the highest GCA effects under optimum conditions (1.4 tha(-1); p < 0.001) and across sites (0.93 tha(-1); p < 0.001). The single-cross hybrids G12 (CML311 x DJL173527) and G16 (DJL173887 x CL1211559) were highly stable and were observed as ideal crosses within both the low-nitrogen and optimal environments. However, G18 (CML311 x DJL173887), which was depicted as ideal genotype under the two management conditions, was an unstable genotype. Hybrid G31 (CML311 x CML312) had the least grain yield under low-nitrogen, optimum and across environments. The hybrid G11 (DJL173527 x CL121290) was the highest yielding genotype amongst the new single-cross hybrids and across environments but was unstable and can be recommended for high potential in environments. Overall, the data demonstrated the potential of single-cross hybrids to supplement TWCH in boosting maize productivity under optimal and nitrogen-stress environments in SSA as well as under other areas with similar climatic conditions in the world.