Context: Development of early maturing maize cultivars that remain productive under low N fertilizer farming system, consistent with the farmers’ technologies is a prerequisite to improving adoption of new varieties without increasing production cost. Objective: To assess the performance of ten early open pollination maize varieties (OPVs) and their F1 hybrids for grain yield and nitrogen use efficiency (NUE), and also identify productive cultivars under low N fertilizer regimes. Materials and Methods: The trials were set up in a split plot arrangement with three N fertilizer levels (0, 45 and 90 kg N ha-1) as main plot and the genotypes as sub-plot. Each plot within N level was four-row, laid out in a randomized complete block design of four replications. Ten OPVs were crossed in a half diallel to generate 45 F1 hybrids during 2004 and 2005 growing seasons. Planting were carried out on 20th July, 2005 and 2nd July, 2006. Agronomic characters studied were grain yield, maize establishment count, days to 50% tasselling and silking as well as plant and ear heights. Results: The year 2005 growing season was better for all observed characters amongst all the genotypes than the year 2006. Although, expressions of these traits in the hybrids were relatively higher than the OPVs including the grain yield. The total increase in grain yield observed was 1.72 t ha-1 and 1.95 t ha-1 for OPVs and hybrids respectively on application of 90 kg ha-1 over no N-application. However, NUE was optimum at 45 kg N ha-1 in both groups. Grain yield and NUE correlated positively with growth characters measured except for days to 50% silking. Higher genetic gains were recorded for plant and ear heights. Conclusion: Two drought tolerant varieties (Acr 90 Pool 16-Dt and Tze Comp3 Dt) that combined well with specific cultivars for grain yield and NUE probably have gene pools for low N-tolerance. DOI: http://dx.doi.org/10.3329/jbs.v19i0.13000 J. bio-sci. 19 43-52, 2011

This study was done to determine the effect of the grain yield and its related characteristics on 10 openpollinated maize varieties and their 45 F 1 hybrids using correlation and path coefficient analysis. A two-year study was conducted on maize genotypes at the University of Ilorin Teaching and Research Farm Ilorin, Nigeria, during 2005 and 2006 growing seasons. Positive and significant phenotypic and genotypic correlations were found for days to 50% tasselling with plant and ear heigh t, and grain yield with plant height, number of grains ear -1 and ear weight. Positive and significant environmental correlation was also recorded for grain yield with plant and ear height, and ear weight. The path analysis revealed that, days to 50% silking, ear weight and number of grains ear -1 had the highest direct effect on grain yield, while number of grains ear -1 had the highest moderate indirect negative effects on grain yield. Days to flowering, plant and ear height, number of grains ear -1 and ear weight could be the important selection criteria in improving open pollinated maize varieties and hybrids for high grain yield.