Space-Planted Condition Abates the GxE Interaction in Maize Inbred Lines and Hybrids.

Strong yield by density interaction resulting in considerable variation in optimum population is a root cause of GxE interaction in maize genotypes. Ultra-low density to ensure absence of competition has been asserted as a unique presupposition to tackle the problem. Thirty-one inbred lines were tested at ultra-low density (ULD) and typical dense stand (TDS) under both normal and water-stressed regimes at three locations. A similar experimentation was followed for 31 hybrids formed by crossing the above lines. In overall, the lines averaged 102 - 697 g/plant and 3,160 - 13,760 kg/ha when spaced and crowded, respectively. The respective values for the hybrids were 645-1,377 g/plant and 8,850 - 13,210 kg/ha. Concerning the inbreds, at the ULD all the 15 among environments linear correlations were very high (r=0.83-0.95, P<0.001); at the TDS two r values were non-significant, eight indicated moderate correlation (0.36-0.56, P<0.05-0.01), and five met the P<0.001 level. For the hybrids, at the ULD all the 15 among environments linear correlations were significant at P<0.001(r=0.69-0.93), while at the TDS just two out of the 15 r values were significant. Consequently, the absence of competition rather than the typical density exhibited less GxE interaction. In terms of inbred lines, assuming the overall yield at the TDS as index of the crop yield potential, it was positively correlated with the across-environment genotype performance at both densities. However, the ULD gave considerably higher r values, hence foresaw better the crop yield. In overall, the results were contrasting with the recommendation that there is no relationship between yield of isolated plants and crop yield, which presumably is valid when tested genotypes are heterogeneous, due to catalytic role of the yielding by competitive ability interference at the dense stand.