Many physiological factors underpin corn yield potential, including source– sink relationship, plant hormones, photosynthetic capability, plant architecture, and general stress tolerance. High plant density imposes intense interplant competition for sunlight, water, and soil nutrients. Increasing tolerance to high plant density is one important strategy to meet goals of doubling corn yield.
Hybrids representing parentage of heterotic subgroups in female and male germplasm pools used in current U.S. commercial corn hybrids were evaluated at plant densities up to 54,000 ppa to identify those with the greatest potential for increasing plant density tolerance. Differences among hybrids were observed for stress response. Inbred parents of the top-yielding hybrids were recombined to generate inbreds for use as parents of testcross hybrids to map chromosomal regions conferring stress tolerance. These regions will be examined, and the results will be translated into new breeding strategies to create higher-yielding lines with increased stress tolerance. Benefits to growers will be greater net profit per acre (i.e., yield increases will overcompensate for higher seed inputs) and reduced risk of yield loss due to weather extremes and other stresses.