Interference competition and aflatoxin levels in corn.

An experiment was designed to determine whether certain fungi commonly isolated from maize at harvest can affect aflatoxin development when inoculated with Aspergillus flavus (NRRL 6412) onto individual sterilized maize kernels (incubation 8 days at 28 deg C). No aflatoxins were detected when A. niger (NRRL 6411) or Trichoderma viride (NRRL 6418) were paired with A. flavus. Aflatoxin contamination was substantial (mean value for B1 ranging from 676 p.p.b. to 3765 p.p.b.) 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 p.p.b.; B2, 1 p.p.b.). 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 spp. colonize a kernel (i.e. prior to, or simultaneous with, the introduction of A. flavus), are examined as factors contributing to variation in aflatoxin levels among field samples.