A review of maize hybrids' dependence on high plant populations and its implications for crop yield stability

Abstract The improved grain yield per unit area of modern maize ( Zea mays L.) hybrids is due to the increased optimum plant population rather than the improved grain yield per plant. Traits associated with tolerance to various stresses, including high plant populations, and the efficiency of capture and use of resources rendered modern hybrids more productive. As a consequence of the improved tolerance to high plant populations and the low yield potential per plant, modern hybrids are strongly population-dependent as their maximum grain yield is achieved only under a narrow spectrum of high plant populations, followed by adverse effects on hybrids’ productivity and stability. Missing plants and unevenness in the plant emergence constitute common problems in the field. Grain yield loss due to missing plants is poorly compensated by the increased yield of the surrounding plants, so grain yield per unit area decreases. Unevenness in the plant emergence leads to increased plant-to-plant variability, the impact being stronger under higher plant populations. Plant-to-plant variability is associated with decreased resource use efficiency, and therefore with reduced grain yield. At higher plant populations reduced grain yield also results from the increased pollen-to-silking interval and the following barrenness. Consequently, maize breeding should seek hybrids that combine population-tolerance and improved yield potential per plant, so that a wider range of optimum plant populations insure both high productivity and stable performance.

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