**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 PHYLLOSPHERE IS ONE OF THE LARGEST NICHES ON THE PLANET AND IS OCCUPIED BY NON-PATHOGENIC YEAST, BUT WE DO NOT HAVE A GOOD UNDERSTANDING OF THEIR ROLES IN DISEASE OUTCOMES AND CROP HEALTH. THEREFORE, TO USE THEM AS TOOLS, IMPROVEMENTS TO THE KNOWLEDGE OF YEAST ECOLOGY ARE NEEDED. LEVERAGING A COLLECTION OF YEAST CULTURES FROM SIX FUNGAL SUBPHYLA AND 33 DISTINCT YEAST LINEAGES, INCLUDING SEVERAL NOVEL SPECIES, THIS PROJECT'S LONG-TERM GOAL IS TO PRODUCE FOUNDATIONAL KNOWLEDGE OF BENEFICIAL YEASTS SO THEY CAN BE USED AS AGRICULTURAL TOOLS. THIS GOAL WILL BE ACCOMPLISHED THROUGH THREE OBJECTIVES: 1) YEAST INTERACTIONS WITH FUNGAL PLANT PATHOGENS AND BENEFICIAL PHYLLOSPHERE BACTERIA, 2) PLANT GROWTH-PROMOTING PHENOTYPES OF YEASTS, AND 3) COMPARATIVE GENOMICS OF NOVEL YEAST LINEAGES. INTERACTION STUDIES WILL IDENTIFY ANTAGONISTIC INTERACTIONS BETWEEN PLANT PATHOGENS AND POSITIVE INTERACTIONS WITH BENEFICIAL BACTERIA. IDENTIFICATION OF YEAST WITH CAPABILITIES TO PRODUCE PLANT GROWTH-PROMOTING COMPOUNDS AND ENZYMES WILL NARROW THE SPECTRUM OF YEASTS TO USE AS CROP INOCULANTS. LASTLY, DRAFT GENOMES OF NOVEL YEAST STRAINS WILL ENABLE THE DISCOVERY OF NOVEL BIOSYNTHETIC GENE CLUSTERS AND ALLOW PLACEMENT ON THE FUNGAL TREE OF LIFE. THESE OBJECTIVES AND THE PLANS ALIGN WITH THE PESTS AND BENEFICIAL SPECIES IN AGRICULTURAL PRODUCTION SYSTEMS PROGRAM BY INVESTIGATING INTRA- OR INTERSPECIES INTERACTIONS AND/OR COMMUNICATION SYSTEMS RELEVANT TO PEST MANAGEMENT AND THE ABUNDANCE OR SPREAD OF AGRICULTURALLY IMPORTANT BENEFICIAL SPECIES. THIS PROJECT WILL ADVANCE THE KNOWLEDGE OF UNDERSTUDIED PHYLLOSPHERE MEMBERS AND HELP MITIGATE THE IMPACTS OF BIOTIC CONSTRAINTS IN FOOD PRODUCTION THROUGH BIO-BASED PRODUCTS.