Project Number: 6402-42000-005-00
Project Type: Appropriated

Start Date: Dec 31, 2011
End Date: Dec 30, 2016

Objective:
The overall objective of this project is the improved biological control of aflatoxin in corn through a more complete ecological understanding of the pathogen and the agroecosystem through applied investigation of biocontrol agent delivery systems. Over the next 5 years our research will focus on the following objectives: Objective 1: Determine the environmental fate of non-toxigenic strains of Aspergillus (A.) flavus using molecular tools. Sub-Objective 1a. Compare DNA sequence information from current biocontrol strains with indigenous strains to identify unique molecular markers. Sub-Objective 1b. Monitor the post-release spatial and temporal distribution of A. flavus biocontrol strains in corn fields. Objective 2: Determine the mechanisms of biocontrol efficacy with non-toxigenic Aspergillus flavus strains. Objective 3: Optimize a water dispersible formulation and application procedure for the use of non-toxigenic strains of Aspergillus flavus for biocontrol of mycotoxins in corn. Sub-Objective 3a. Develop and evaluate water dispersible granular (WDG) formulation of non-toxigenic Aspergillus flavus strains. Sub-Objective 3b. Evaluate the Accu-Flo™ spray nozzle for aerial application of biological materials. Sub-Objective 3c. Determine the effect of timing of the application of K49 and Afla-Guard® as a WDG formulation. Sub-Objective 3d. Compare the effect of a combined inoculum of K49 and Afla-Guard® to these inoculants used separately.

Approach:
Maize (corn) production in the United States is valued at $65 billion annually. Infection of corn by some strains of Aspergillus (A.) flavus, and subsequent contamination with the mycotoxin aflatoxin, results in costs of $923 million (UN Food and Agriculture Organization) and illnesses, including cancer or death in livestock and humans. Fungicides, altered agronomic practices and breeding efforts, including the use of transgenic Bt-corn have all been insufficient in mitigating aflatoxin contamination. Presently, the most effective approach to reduce aflatoxin contamination in corn is biological control, using non-aflatoxin-producing strains of A. flavus, as developed by USDA-ARS researchers. This technology is now commercially available as Afla-Guard®. Substantial progress has been made in the implementation of this product, but important research questions remain, which are addressed in this proposal: First, the post-release environmental fate of non-toxigenic strains of A. flavus must be evaluated. This is an essential environmental stewardship issue and may yield insight into A. flavus ecology and the plant disease cycle. Another objective includes experiments to evaluate mechanisms of biological control, including a model to explain why biocontrol strains are more effective at reducing aflatoxin contamination than predicted by simple competition. Finally, improvements in formulation and application methods of A. flavus biocontrol strains are needed for better, more consistent aflatoxin control. The commercialization of Afla-Guard® was important in the effort to exclude aflatoxin from food and feed. The basic and applied research in this proposal is essential to complete the implementation of the biocontrol strategy for reducing aflatoxin contamination of corn.