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Postharvest Pathology and Mycotoxins

Fungal Interference with Aspergillus flavus Infection and Aflatoxin Contamination of Maize Grown in a Controlled Environment. D. T. Wicklow, Northern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604; B. W. Horn, O. L. Shotwell, C. W. Hesseltine, and R. W. Caldwell. Department of Plant Pathology, University of Wisconsin, Madison. Phytopathology 78:68-74. Accepted for publication 10 June 1987. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/Phyto-78-68.

The ability of 'competing fungi' in preharvest maize to interfere with Aspergillus flavus infection and aflatoxin contamination of developing kernels was examined. Experiments were conducted in a plant growth room to eliminate insect damage of the ear, contaminating fungi, and unpredictable climatic events. Silk inoculation of uninjured ears resulted in fewer than 2% A. flavus-infected kernels and no detectable aflatoxin. Sterile toothpick-wounding of several kernels on ears that were similarly silk-inoculated promoted substantial A. flavus infestation and aflatoxin contamination of the wounded kernels. Many of the uninjured kernels also became infected with A. flavus. Kernel wounding by toothpick also promoted ear infection by Fusarium moniliforme, Acremonium strictum, and Aspergillus niger. When kernels were directly wound-inoculated with A. flavus and competing fungi, high levels of aflatoxins were detected in both the wounded kernel tissues and the first surrounding circle of uninjured kernels. However, the competing fungi, particularly F. moniliforme, inhibited A. flavus from further infecting and contaminating the other uninjured kernels on the same ear with aflatoxin.