Pre-harvest silk treatment with Trichoderma harzianum reduces aflatoxin contamination in sweetcorn

Abstract

One of the most promising management tools to reduce mycotoxins in food and feed is the pre-harvest biological control of mycotoxigenic fungi using microbes. The goal of this investigation was to evaluate the potential of a stain of Trichoderma harzianum, T77, for control of Aspergillus flavus on sweetcorn. Under greenhouse and field conditions, T. harzianum was applied as a pre-harvest spray treatment to silks of sweetcorn plants at 1, 3, 6, 8, 10, 12 and 14 days post-midsilk. Toxigenic A. flavus was spray inoculated as a conidial suspension (103 spores ml−1) onto silks at 2, 4, 7, 9, 11 and 13 days post-midsilk. Percentage kernel infection, disease ratings, ELISA and HPLC analyses were used to quantify A. flavus infection and aflatoxin contamination. There was a significant reduction in toxigenic A. flavus infection and aflatoxin contamination after silk spray treatments with T77 at 10 and 12 days post-midsilk. In vitro dual culture bioassays and ultrastructural studies using environmental scanning electron microscopy revealed antibiosis and mycoparasitism are the probable modes of action. It thus can be seen that pre-harvest spray treatment of sweetcorn at the silk growth stage can reduce the level of A. flavus contamination of grain. An integrated approach consisting pre-harvest biological control using selected strains of T. harzianum in conjunction with other post-harvest management strategies could reduce A. flavus infection and aflatoxin contamination in grain.