MANAGING CROP MICROBIOMES FOR ENHANCED PRODUCTIVITY AND DISEASE RESISTANCE IS A MAJOR CHALLENGE GIVEN THEIR TAXONOMIC AND FUNCTIONAL COMPLEXITY. ON THE OTHER HAND, MANAGING A DISCRETE COMPONENT OF THE MICROBIOME MAY BE A MORE REALISTIC GOAL IF WE CAN SELECTIVELY BREED FOR PLANT GENOTYPES THAT ARE ENRICHED IN A TAXONOMIC GROUP THAT IS BENEFICIAL TO PLANTS, OR MANIPULATE PLANT GENOMES TO PROMOTE PARTICULAR BENEFICIAL PLANT-FUNGAL SYMBIOSES. THE PROPOSED STUDY WILL ADVANCE SUSTAINABLE DISEASE MANAGEMENT IN AGRICULTURAL SYSTEMS BY CONTRIBUTING TO THE DEVELOPMENT OF PLANT GENETIC IMPROVEMENT TARGETS THAT FACILITATE PLANT DISEASE SUPPRESSION BY EPIPHYTIC YEASTS. WE WILL DO THIS BY LEVERAGING PLANT GENOMIC RESOURCES IN THE MODEL TREE, POPULUS TRICHOCARPA, TO IDENTIFY PLANT SNPS/GENES ASSOCIATED WITH THE ABUNDANCE OF EPIPHYTIC YEAST SPECIES AND THEIR ANTAGONISM OF A LEAF RUST PATHOGEN. WE WILL ADDITIONALLY EXPLORE YEAST-PATHOGEN ANTAGONISM IN THE CONTEXT OF A SYNTHETIC COMMUNITY, ASKING WHETHER YEAST ARRIVAL ORDER INTO THE COMMUNITY IMPACTS DISEASE SUPPRESSION. WE EXPECT THAT RESULTS OF OUR PROJECT WILL REVEAL THE POTENTIAL FOR PLANT GENETIC IMPROVEMENT OPTIMIZING BOTH EPIPHYTIC YEAST COLONIZATION AND YEAST PRIORITY EFFECTS FOR ROBUST DISEASE CONTROL. THIS NOVEL APPROACH TO DISEASE MANAGEMENT HAS THE POTENTIAL TO BE BOTH SAFER AND MORE SUSTAINABLE THAN THE USE OF CONVENTIONAL PESTICIDES. OUTCOMES OF THE PROPOSED RESEARCH ADDRESS TWO KEY USDA AFRI PROGRAM AREAS: PLANT HEALTH AND PRODUCTION, AND BIOENERGY, NATURAL RESOURCES AND THE ENVIRONMENT.