Genetic gains in three breeding eras of maize hybrids under low and optimum nitrogen fertilization
2014
Bello, Omolaran B. (Fountain University, Osogbo (Nigeria). Department of Biological Sciences) | Olawuyi, Odunayo J. (University of Ibadan, Ibadan (Nigeria). Depatment of Mathematical and Computer Sciences) | Lawal, Mohammed (Fountain University, Osogbo (Nigeria). Department of Biological Sciences) | Ige, Sunday A. (University of Ilorin, Ilorin (Nigeria). Department of Agronomy) | Mahamood, Jimoh (Lower Niger River Basin Development Authority, Ilorin (Nigeria)) | Afolabi, Micheal S. (Landmark University, Omuaran (Nigeria). Department of Crop Science) | Azeez, Musibau A. (Ladoke Akintola University of Technology, Ogbomoso (Nigeria). Department of Pure and Applied Biology) | Abdulmaliq, Suleiman Y. (Ibrahim Badamasi Babangida University, Lapai (Nigeria). Department of Agronomy)
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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