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POSTERS: Biological control

Genetic factors influencing the efficacy and persistence of biocontrol of aflatoxin contamination in maize
Jane Marian Luis - CIFR, Dept of Entomology and Plant Pathology, North Carolina State University. Mark Weaver- USDA-ARS, Biological Control of Pests Research Unit, Kira Bowen- Dept of Entomology and Plant Pathology, Auburn University, Ron Heiniger- Dept of Crop Science, North Carolina State University, Thomas Isakeit- Dept of Plant Pathology and Micro

A large acreage of maize grown in the southern United States is chronically at risk of aflatoxin contamination caused by Aspergillus flavus. Biocontrol treatments using atoxigenic strains of A. flavus can reduce contamination by up to 95%. Commercial biocontrol strains are of the mating type MAT1-2 and are applied annually for effective performance. Currently, there is interest in the development of sustainable biocontrol approaches to successfully reduce aflatoxin contamination. First, we examined the efficacy of RMb10, a novel biocontrol strain of the MAT1-1 type, in replicated large-scale field trials in AL, MS, NC, and TX from 2016 to 2018. Second, we investigated the genetic factors that may influence the persistence of biocontrol strains in the field. Isolates (n = 300) of A. flavus were collected from specific maize fields in MS, NC, and TX. These fields had 3 to 7 years history of annual Afla-Guard treatment, but applications were terminated when harvested grain exhibited no aflatoxin contamination in subsequent seasons. In both experiments, isolates were screened for colony morphology, sclerotia production, mating type, and aflatoxin cluster composition, and then subjected to multi-locus sequencing using five loci (amdS, aflM, aflW, mfs, and trpC). Results of this study will provide insights into the population genetic structure of fields with reduced contamination and inform future biocontrol strategies.