Trial summary on the comparison of various non-aflatoxigenic strains of aspergillus flavus on mycotoxin levels and yield in maize

Abstract

The fungus Aspergillus flavus can contaminate maize (Zea mays L.) by producing aflatoxins (AFs), secondary metabolites that have been shown to have adverse health impacts for humans and animals when ingested in large quantities or over extended lengths of time. The FDA strictly regulates that corn contaminated with more than 20 parts per billion (ppb) AFs cannot be marketed for human consumption; therefore, AFs cost US corn growers billions of dollars every year. Current methods to curb aflatoxin contamination in fields involve dense applications of non-aflatoxigenic biological control (biocontrol) strains, either Afla-Guard or AF36, that outcompete native strains and reduce toxicity levels throughout the field. This fungus is heterothallic and sexual reproduction occurs between isolates of opposite mating types, either MAT1-1 or MAT1-2. Both biocontrol strains are of a single mating type MAT1-2. The implications of adding a strain of opposite mating type (MAT1-1) to this formulation are unknown. Here we examine the ability of native non-aflatoxigenic strains applied singly and in combination to reduce AF concentrations in a cornfield in Rocky Mount, NC. We show that native, non-aflatoxigenic A. flavus strains reduced aflatoxin levels and increased yield when compared with untreated controls. Moreover, the strain formulations that included sexually compatible MAT1-1 and MAT1-2 strains showed the greatest reduction in aflatoxin levels. We propose that using a combination of native isolates of opposite mating types reduces AF levels further than current biocontrol agents of a single mating-type strain and could potentially provide a more long-term form of control.