Traits Related to Kernel Setting of Subapical Ear in Maize Hybrids.

Maize grain yield is generally optimized with high population densities at which only apical ears contribute to total kernel number per area. Under limited conditions, however, low plant population densities are used and fertile sub-apical ears may contribute to total grain yield. In this work we have explored different traits related to prolificacy (i.e. number of fertile ears per plant) of four commercial maize hybrids (DK3F22, DK752, DK747, DK7210) released during the last four decades (1970, 1990, 2000 and 2010). Mentioned hybrids were cultivated at low (4 plants/m2), optimum (8 plants/m2) and high (12 plants/m2) plant population densities and several measurements were performed around flowering to analyze plant growth rate, biomass partitioning to ears, reproductive efficiency and the synchrony of flowering of both ears. Contribution of kernels of the sub-apical ear to total kernel number per area varied from 0 to 31 percent (i.e. at the highest and lowest plant density, respectively). Plant density and hybrid effects on prolificacy and kernel number of sub-apical ear were reflected on the contribution of kernels of sub-apical ear to total kernel number per unit area.  Thus, at the lowest plant density, the oldest genotype (DK3F22) exhibited the lowest prolificacy with the lowest kernel setting. Hence, total kernel number per unit area of modern hybrids (DK747 and DK7210) at the lowest plant density resulted similar than that of the oldest hybrid at the optimum plant density. Differences among genotypes in prolificacy and kernel setting of sub-apical were mainly determined by biomass partitioning to ears around flowering.