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Postharvest Pathology and Mycotoxins

Interference Competition and Aflatoxin Levels in Corn. D. T. Wicklow, Research microbiologist, Northern Regional Research Center, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Peoria, IL 61604; C. W. Hesseltine(2), O. L. Shotwell(3), and G. L. Adams(4). (2)(3)(4)Laboratory chief, research leader, and biological laboratory technician, respectively, Northern Regional Research Center, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Peoria, IL 61604. Phytopathology 70:761-764. Accepted for publication 1 February 1980. 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, 1980. DOI: 10.1094/Phyto-70-761.

An experiment was designed to determine whether certain fungi commonly isolated from corn at harvest can affect aflatoxin development when inoculated with Aspergillus flavus (NRRL 6412) onto individual sterilized corn kernels (incubation 8 days at 28 C). No aflatoxins were detected when Aspergillus niger (NRRL 6411) or Trichoderma viride (NRRL 6418) were paired with A. flavus. Aflatoxin contamination was substantial (mean values for B₁ ranging from 676 ppb to 3,765 ppb) in 11 other simultaneous pairings. When inoculation with A. flavus followed by 5 days that of the other test fungi, aflatoxin was detected only in pairings with Candida guilliermondii (B₁, 16 ppb; B₂, 1 ppb). However, A. flavus invaded a number of the other preinoculated kernels in this series, as evidenced by its abundant sporulation on kernel surfaces and/or the formation of a bright greenish-yellow (BGY) fluorescence in kernel tissues examined under black light (365 nm). The status of individual fungal colonists as interference competitors, and the order in which species colonize a kernel (ie, prior to, or simultaneous with, the introduction of A. flavus), are examined as factors contributing to variation in aflatoxin levels among field samples.