Resistance to fungi causing deterioration of corn stalks late in the season is complicated. Fusarium, Gibberella and Diplodia species usually identified with rotten stalks were on and nearly all the plants in the field all season, successfully stopped by the corn plants from destroying the plants. Even if artificially inoculated into the stalks by puncturing the lower stalk and inserted into the stalk pith tissue, these fungi rarely can kill the plant in any manner suggesting simple resistance genetics. Living vigorous cells in the pith react to the presence of these fungi by limiting their growth within the tissue.
Corn varieties do differ in the tendencies to get these late-season stalk rots. Although every plant in a field is exposed to the same fungi stalk rots show in isolated plants, in some areas of the field in some years despite all plants within a single-cross hybrid having the same genetics. This distribution pattern strongly supports the interaction of environmental factors with the occurrence of stalk rot.
Plants that develop stalk rot also have rotting roots, causing the plants to wilt. Roots rotted because they received insufficient photosynthates to maintain defense against the many soil organisms capable of digesting root cell contents. Resulting plant wilting caused senescence and death of the cells in the stalk pith. Consequently, the many fungi surrounding the stalk and in the soil moved through the stalk, destroying the cellular strength.
Stalk rot resistance genetics involves those affecting photosynthesis. This must include structures and physiology basic to production of carbohydrates- leaf size and shape, mineral uptake and utilization, stomata function and number.
Stalk rot resistance genetics must also involve how the carbohydrates are distributed and utilized. The balance of transporting sufficient energy to the root cells for maintenance of vigorous defense against soil microbes and the competing movement of carbohydrates to the developing grain involves multiple genetics for structure and physiology.
These genetic complexities and strong environmental influences leaves us with only being able to express the tendencies of a hybrid to get stalk rot. It is complicated!
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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.