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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Research Project #430864

Research Project: Improved Environmental and Crop Safety by Modification of the Aspergillus flavus Population Structure

Location: Pest Management and Biocontrol Research

2016 Annual Report

1. Optimize and expand use of biological control of aflatoxins based on atoxigenic strains of Aspergillus flavus in order to improve access, affordability, and area-wide management. Subobjective 1.1. Evaluate area-wide influences where atoxigenic biopesticides are widely used and develop strategies to increase cost-savings and efficacy based on area-wide effects. Subobjective 1.2. Evaluate the potential to adapt hydropriming from seed technology to use with atoxigenic strain products to increase atoxigenic strain release under low humidity. Subobjective 1.3. Advance biological control products based on atoxigenic strains of A. flavus with commercial field testing. Subobjective 1.4. Improve access to atoxigenic strain biopesticides by assisting stakeholders to reduce costs of manufacture and distribution and expand biopesticide products while engaging USEPA in dialogue on biocontrol regulatory issues and public sector roles. 2. Develop an understanding of the distribution of Aspergillus flavus genetic haplotypes and vegetative compatibility groups worldwide in order to improve selection of biological control agents. Subobjective 2.1. Identify A. flavus endemic in and adapted to target agroecosystems. Subobjective 2.2. Determine utility of SSRs in tracking mechanisms and histories of divergences within A. flavus. Subobjective 2.3. Develop an SSR database to support global efforts to delineate distributions of A. flavus genotypes and relationships among strains under investigation in diverse locations. 3. Improve understanding of development, evolution, and stability of populations of Aspergillus flavus, including phenomena occurring both within and between VCGs, in order to inform to inform optimization of long-term beneficial effects of atoxigenic strain biocontrol. Subobjective 3.1. Determine the nature of clonal evolution in A. flavus with genomic analyses. Subobjective 3.2. Assess mutation rate in an A. flavus genome during asexual reproduction in controlled laboratory evolution studies.

Biological control products, developed during previous projects, with atoxigenic strains of Aspergillus flavus as active ingredients have been successful at greatly reducing aflatoxin contamination of corn and peanut in commercial fields in the US and in thousands of farmer’s fields across Nigeria, Kenya, Senegal, Burkina Faso, Zambia, the Gambia, and Ghana. The current project seeks to improve biological control to increase both single-season and long-term aflatoxin management to provide a context for both efficient area-wide aflatoxin management and reductions in cost of biological control programs. Area-wide influences of current commercial practices utilizing atoxigenic strain biocontrol agents will be quantified with culture and DNA based techniques. Diversity among and distributions of naturally occurring atoxigenic strains of potential use in biological control products will be determined and atoxigenics will be selected and field tested for the next generation of aflatoxin prevention biocontrol products. Simple Sequence Repeat (SSR) analyses will be expanded to allow better understanding of strain distribution and divergence. A worldwide SSR database for A. flavus will be developed to allow the global scientific community to identify genotypes reported in the literature and/or incorporated into biocontrol products under development around the world. Comparative genomic analysis will be performed to characterize adaptation, divergence, and the relative contributions of recombination and clonality to A. flavus community structure. The resulting information will provide improved cost effective tools for production of safe foods and feeds.

Progress Report
This is the first report for this new project which began on May 26, 2016 and continues research from the previous project, 2020-42000-021-00D, "Reducing Aflatoxin Contamination Using Biiological Control and Crop Management". See the report for the previous project for additional information. We are selecting study areas with collaborators in Texas and California to begin the first year assessment of commercial strip treatments. A request for an experimental use permit for atoxigenic biocontrol product production is being prepared and submitted to the Environmental Protection Agency (EPA). This experimental program, once approved, will be a component of the new project. Simple sequence repeats (SSR) are being run to increase the total characterized isolates. We continued to improve molecular tools needed for the new project. This included developing and refining a pipeline to perform SSR analyses of 20,000 Aspergillus flavus isolates during the next five years, collection of A. flavus isolates of potential value to upcoming projects, and collaborating with industry partners in mitigating aflatoxin contamination related issues. Field trials for the 2016 season proceeded in collaboration with pistachio, corn, and cotton farmers in order to improve recommendations for and implementation of biological control with atoxigenic strain based products. Genomics, population genetics, and microbiological approaches continued in efforts to better determine the risks and benefits of using atoxigenic strains of Aspergillus flavus to prevent aflatoxin contamination and also to improve the abilities of U.S. industries and farmers across the globe to use atoxigenic strain based biocontrol to alleviate the burdens of aflatoxin contamination. Cooperative research endeavors with colleagues in several nations will also serve to assist development of the database required by the new project. These pending, initiating or continuing collaborations include Haiti, Costa Rica, Senegal, Nigeria, Zambia, Tanzania, Kenya, Mozambique, Rwanda, Burundi, Malawi, and Uganda.