Genetic gains in three breeding eras of maize hybrids under low and optimum nitrogen fertilization

Department of Biological Sciences, Fountain University, Osogbo, Osun State, Nigeria (1)
Depatment of Botany and Microbiology, University of Ibadan, Oyo State, Nigeria (2)
Department of Mathematical and Computer Sciences, Fountain University, Osogbo, Osun State, Nigeria (3)
Department of Agronomy, University of Ilorin, Kwara State, Nigeria (4)
Lower Niger River Basin Development Authority, Ilorin, Kwara State, Nigeria (5)
Department of Crop Science, Landmark University, Omuaran, Kwara State, Nigeria (6)
Department of Pure and Applied Biology, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria (7)
Department of Agronomy, Ibrahim Badamasi Babangida University, Lapai, Niger State, Nigeria (8)


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A comparative study on the response of six maize hybrids: two hybrids each from the 1980s (8321-21 and 8425-8), 1990s (9801-11 and 9803-2) and 2000s (0103-11 and 0103-15) to sub-optimal and optimal nitrogen fertilization was conducted in Oke-Oyi, Nigeria. The trials were set up in a split plot with three nitrogen levels (0, 30 and 90 kg N ha-1) as a main plot and six hybrids as sub-plots. Significant interactions were observed between hybrid and N level for all characters, with increasing in variation as the level of N decreased. Mean grain yield reductions across eras were 73.8% at no-N and 32.6% at low-N, and those of optimal-N fertilization were 34.3% and 15.7% for 1980s and 1990s genotypes respectively. Depending on N treatment, grain yield varied from 0.67 to 4.89 t ha-1. Kernel number was most severely reduced by N stress, but had positive and highly significant (p≤0.01) correlation with grain yield at all N levels. Genetic gains in grain yield were 42% (between 1980 and 2000 eras) and 9% (between 1990 and 2000 eras) under optimal-N fertilization. The two modern hybrids of 2000 era (0103-11 and 0103-15) were outstanding for all the agronomic traits and leaf chlorophyll concentration at all N levels. Improving traits associated with fertilizer N response could accelerate rate of genetic gains in maize yields.

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