**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** FUNGAL PATHOGENS CAUSE SIGNIFICANT LOSSES OF CROP YIELD AND ARE A SERIOUS BIOLOGICAL THREAT TO FOOD SECURITY. EFFECTIVE MANAGEMENT OF FUNGAL DISEASES IN CROPS HAS BECOME A MAJOR CHALLENGE DUE TO DEVELOPMENT OF FUNGICIDE RESISTANCE IN PATHOGEN POPULATIONS AND LACK OF SINGLE GENE RESISTANCE. THUS, IT IS IMPORTANT TO LOOK FOR COUNTERMEASURES. SMALL CYSTEINE-RICH ANTIFUNGAL PEPTIDES THAT EXHIBIT POTENT ANTIFUNGAL ACTIVITY AGAINST ECONOMICALLY IMPORTANT FUNGAL PATHOGENS OFFER PEPTIDE-BASED BIOFUNGICIDE ALTERNATIVES TO ON-FARM CHEMICAL FUNGICIDES. WE HAVE IDENTIFIED TWO SMALL ANTIFUNGAL PEPTIDES FROM LEGUMINOUS PLANTS THAT OFFER SIGNIFICANT POTENTIAL FOR DEVELOPMENT AS SECOND-GENERATION SAFE AND SUSTAINABLE BIOFUNGICIDES. FOR EFFECTIVE USE OF THESE PEPTIDES FOR CROP PROTECTION IN AGRICULTURE, IT IS IMPORTANT TO UNDERSTAND THEIR STRUCTURE-ACTIVITY RELATIONSHIPS AND MECHANISMS OF ANTIFUNGAL ACTION. PRELIMINARY STUDIES HAVE REVEALED THAT THESE PEPTIDES EXHIBIT MULTI-FACETED MODES OF ACTION. INTHIS PROPOSAL, ACTIVE SITES OF THESE PEPTIDES GOVERNING THEIR ANTIFUNGAL ACTIVITY WILL BE DETERMINED AND EXTENSIVE HIGH-RESOLUTION MICROSCOPY WILL BE USED TO INVESTIGATE SUBCELLULAR TARGETS OF THESE PEPTIDES IN A FUNGAL PATHOGEN THAT CAUSES GRAY MOLD DISEASE IN FRUITS AND VEGETABLES. FURTHER, BIOCHEMICAL TOOLS WILL BE EMPLOYED TO IDENTIFY MOLECULAR TARGETS OF THESE PEPTIDES IN THE FUNGUS. THIS PROJECT PROVIDES INTERDISCIPLINARY TRAINING TO A POSTDOCTORAL STUDENT AND A TECHNICIAN.