Location: Pest Management and Biocontrol Research
Project Number: 2020-42000-023-000-D
Project Type: In-House Appropriated
Start Date: May 26, 2021
End Date: May 25, 2026
Objective:
Objective 1: Characterize Aspergillus section Flavi diversity and population dynamics in response to biotic and abiotic factors with a focus on the soil environment. Sub-objective 1A: Characterize Aspergillus section Flavi diversity in target agroecosystems and develop/refine tools for typing and quantifying specific genotypes in the environment. Sub-objective 1B: Evaluate the survival, growth, and dispersal of biocontrol strains (atoxigenics) versus high aflatoxin producers in response to biotic and abiotic factors with a focus on the soil environment. Objective 2: Elucidate molecular mechanisms involved in aflatoxin degradation by atoxigenic Aspergillus flavus. Objective 3: Identify management practices that will increase the efficacy and reduce the cost of aflatoxin biocontrol in diverse cropping systems. Sub-objective 3A: Evaluate impact of co-applied agrochemicals on aflatoxin biocontrol efficacy. Sub-objective 3B: Optimize management recommendations for area-wide aflatoxin management with atoxigenic-based biopesticides in tree crops. Sub-objective 3C: Evaluate efficacy of aflatoxin biocontrol and develop aflatoxin management recommendations for silage corn.
Approach:
Sub-objective 1A: Global populations of Aspergillus flavus and related species will be characterized to identify genotypes that are dominant in target agroecosystems and to provide genomic targets useful for typing and tracking those lineages in the environment. Isolates of A. flavus will be provided by U.S. and international collaborators. Isolates will be genotyped using simple sequence repeat (SSR) markers, and data will be added to the previously developed SSR database (AflaSat). Molecular assays that distinguish between species/genotypes will be designed based on whole genome sequencing of multiple species/isolates within Aspergillus section Flavi. Sub-objective 1B: A series of soil microcosm experiments aimed at understanding A. flavus population dynamics in agricultural soils will be conducted. The focus will be on competition between non-aflatoxigenic biocontrol strains of A. flavus and high aflatoxin-producing S strain A. flavus in soil. Experiments will be conducted in different soil types, in autoclaved versus non-autoclaved field soil, and at different soil temperatures and moisture contents. Influences of treatments on survival, growth, and sporulation of non-aflatoxigenic and S strain A. flavus will be assessed using a combination of culture- and DNA-based methods. Objective 2: The phenomenon of aflatoxin degradation by non-aflatoxigenic A. flavus isolates will be assessed using transcriptomic analysis. Changes in gene expression in the presence or absence of aflatoxin and glucose as carbon sources will be used to identify potential mechanisms of aflatoxin degradation. In addition, a metabolomic study will determine products of aflatoxin degradation by non-aflatoxigenic A. flavus. Sub-objective 3A: A combination of laboratory, small plot, and large-scale field studies will be used to assess impacts of fertilizer, herbicide, insecticide, and fungicide co-treatments on efficacy of aflatoxin biocontrol. Sporulation of biocontrol strains on formulated products and growth of active ingredient strains will be quantified with and without exposure to co-treatment agrochemicals. Sub-objective 3B: Movement and persistence of an applied non-aflatoxigenic biocontrol strain will be quantified in a tree crop production area in Arizona. Soil will be collected from biocontrol treated pistachio orchards, non-treated tree crop orchards, fields with an annual crop (e.g., corn, cotton), and crop-adjacent desert lands. Sampling will be conducted along transects with increasing distance away from biocontrol treated areas. This will allow for quantification of biocontrol strain movement across the landscape in a tree crop production area. Sub-objective 3C: Efficacy of aflatoxin biocontrol products will be assessed in commercial fields of silage corn in Arizona. Soil will be collected prior to biocontrol application and following harvest. Chopped samples of corn silage will be sampled immediately following harvest and monthly from silage piles. Percentages of A. flavus in soil and on the crop belonging to the same genotype as the applied biocontrol strain will be quantified, and aflatoxin concentrations in silage will be measured.
