It is corn harvest time in the Northern hemisphere. Benefits of genetic diversity in this species becomes increasingly evident at harvest time. Grain yields vary among the hybrids and environments. Differences were the culmination of the multiple genetically influenced morphological features. Roots that extended deep in the drier environments provided access to more water, increasing the turgor pressure for silk elongation during the time of exposure to pollen. On the other hand, if the post flowering environment was extremely wet this tap-rooted hybrid type could be vulnerable to root lodging. The hybrid with shallow, branching roots favored in organic rich soils favored by frequent rain during the season, may not have had enough turgor to push out these silks during much of the pollen shedding time, harming the grain yield.
Leaf size and shape differences were factors in photosynthetic rates among hybrids. These morphological features interacted with plant density, fertilizer and sunlight intensity of the summer to affect carbohydrate production by the plants. Leaf disease resistance affected net photosynthesis during the season. Genetic differences among hybrids for reaction to accumulated heat influenced the timing of pollination. Longer time to flowering allowed for more accumulation of carbs in the stalk and more reserve for grain fill if late season stresses reduced photosynthesis. Genetically influenced differences in vascular tissue structure affected the rate of movement to sugars to the grain. Varieties differed in hormone influenced rate of movement to each kernel. Duration of sugar translocation after pollination was also affected by genetics. Ability of roots to maintain life when under the competitive pressure from grain filling was another difference among hybrids.
Kernel feature differences become visible, especially to corn breeders as they harvest nurseries. Endosperm texture differences are evident. Yellow colors vary in intensity, with simply inherited traits such as blue, red and white endosperms being most extreme. Shape and length of the ear are inherited traits contributing to the grain yield and drying characters of the hybrid. Less obvious genetically influenced character such as pericarp thickness are important to grain drying after formation of the abscission layer at the base of the kernel. Genetics affected the number and length of husk leaves surrounding the ear. This affected protection of grain from pests but also field drying of the grain.
As we observe the diversity of corn genetics we should appreciate that 8000 years of human interaction with this species as resulted in a diverse crop adapted to multiple environments across the earth. Each season, in each field, may favor different specific genetics but diversity is the key to the long-term success of this efficient converter of light into useful stored energy.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.