Variability in corn hybrid resistance to preharvest aflatoxin contamination

Abstract

AbstractPreliminary field studies suggested evidence for resistance of certain corn hybrids to the preharvest infection of kernels byA. flavus and contamination of the kernels with aflatoxin before harvest. A major constraint in evaluating corn hybrids for resistance to the contamination has been the unusual heterogeneity associated with the toxin distribution. A few kernels containing high levels of toxin are routinely responsible for contamination of large sample lots. Extraordinary heterogeneity is also observed in toxin occurrence among fields within a region and among large geographic areas. Edaphic and climatic differences appear to render immature kernels susceptible to aflatoxin accumulation in a discontinuous manner. To reduce intrinsic variability and acquire definitive information on hybrid differences in susceptibility to contamination, several techniques have been developed including: (a) an increase in the number of regional test sites, (b) expansion of the sample sizes, (c) an increase in replication numbers, and (d) elevation of toxin levels in kernels by experimental treatments. Reduction of test variability has allowed for delineation of hybrid differences in aflatoxin resistance. In a diallel set study, genotypes have been identified with heritable qualities of reduced aflatoxin levels in developing kernels. These results provide a basis for further characterization of a genetic facility for resistance to the toxin‐producing fungi; these factors have the potential for incorporation into commercial hybrids.