Six tropical maize inbred lines were crossed in a half diallel fashion and evaluated along with their F1 hybrids under iow N (0 kg/ha) and high N(170 kg/ha), for grain yield, ear diameter, ear length,number of rows per ear, 100-kernel weight, ear leaf area, shoot dry weight, ear leaf chlorophyll content and plant height to determine their response to different level of N. Grain yield and ear leaf chlorophyll content measured by 48% lower under -N than under + N, and were most affected by -N. Ear length had the highest reduction under -N of 22%. Plant height and shoot dry weight were both reduced by 28%. Diallel analysis indicated significant additive as well as dominance variance for grain yield under -N. The same results were shown when one tolerant × nontolerant cross from the diallel hybrids was subjected to generation mean analysis which also indicated significant epistatic effects. These results suggest that S1 or S2 progeny selection may be an effective means of improving grain yield of tropical maize under low soil N.
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