**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE SOYBEAN CYST NEMATODE (HETERODERA GLYCINES; SCN) IS ONE OF THE MOST DESTRUCTIVE AND DIFFICULT TO MANAGE ROOT PATHOGENS OF SOYBEAN. SOILS UNDER NO-TILLAGE AND LONG-TERM SOYBEAN MONOCULTURE HAVE BEEN SHOWN TO SUPPRESS AND MAINTAIN LOW LEVELS OF THIS PATHOGEN IN SOIL. ALTHOUGH SOME BACTERIA AND FUNGI HAVE BEEN IDENTIFIED FROM THESE SOILS, WHICH SPECIES ARE INVOLVED IN SUPPRESSION AND HOW THEY CONTROL NEMATODE LEVELS IN SOIL ARE NOT WELL UNDERSTOOD. COMBINATIONS OF NEMATODE PARASITIC MICROBES HAVE OFTEN SHOWN GREATER EFFICACY THAN INDIVIDUAL SPECIES, DUE IN PART TO INTERACTIONS OF MICROBES IN THE SOIL. THIS PROJECT AIMS TO IMPROVE OUR UNDERSTANDING OF MICROBIAL SPECIES INTERACTIONS INVOLVED IN SUPPRESSING THE SCN. USING HIGH-THROUGHPUT GENOME SEQUENCING AND CHARACTERIZATION OF GENES HIGHLY EXPRESSED IN SUPPRESSIVE SOILS, WE WILL IDENTIFY KEY TAXA, SPECIES INTERACTIONS, GENES, AND METABOLITES IN SCN SUPPRESSIVE SOILS. USING COMPUTER NETWORK MODELLING, WE WILL ANALYZE THIS DATA TO IDENTIFY INTERACTIONS BETWEEN MICROBIAL SPECIES THAT MAY BE RESPONSIBLE FOR NEMATODE SUPPRESSION. FINALLY, BASED ON THESE RESULTS, WE WILL SELECT AND TEST COMBINATIONS OF SEVERAL MICROBIAL SPECIES IN PLANT BIOASSAYS FOR THEIR ABILITY TO CONTROL THE SCN. THIS RESEARCH WILL ADVANCE THE USE OF MICROBES FOR DEVELOPMENT OF ECOLOGICALLY AND ECONOMICALLY SUSTAINABLE CONTROL OF THE SCN.