** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** COMMERCIALLY VALUABLE ESSENTIAL OILS ARE OBTAINED BY HYDRODISTILLATION FROM VARIOUS AROMATIC HERBS AND TREES. UNFORTUNATELY, EFFORTS AIMED AT ENHANCING EXISTING CULTIVARS HAVE MET CRITICAL CHALLENGES, AS COMMERCIALLY GROWN CULTIVARS ARE OFTEN STERILE, POLYPLOID HYBRIDS. WE HAVE MADE CONSIDERABLE PROGRESS WITH AN APPROACH THAT BUILDS ON THE UNDERSTANDING THE DETERMINANTS OF OIL BIOSYNTHESIS IN DIPLOID ACCESSIONS OF SPECIES ANCESTRAL TO COMMERCIAL POLYPLOIDS OF MINT. SPECIFICALLY, WE HAVE (I) ANALYZED OVER 200 DIVERSE MINT ACCESSIONS FOR OIL CHARACTERISTICS, (II) GENERATED A CHROMOSOME-LEVEL ASSEMBLY OF THE GENOME OF A DIPLOID MODEL MINT SPECIES ANCESTRAL TO POLYPLOID SPEARMINT AND PEPPERMINT, AND (III) DEMONSTRATED THE FEASIBILITY OF INTRA- AND INTER-SPECIES CROSSES BETWEEN DIFFERENT MINT ACCESSIONS. OUR CENTRAL HYPOTHESIS IS THAT THE FUNCTIONALIZATION ENZYMES INVOLVED IN MINT MONOTERPENOID BIOSYNTHESIS ARE PROMISCUOUS, THUS ENABLING THE DEVELOPMENT OF NOVEL, VALUE-ADDED SPECIALTY OILS. BUILDING ON THE SUBSTANTIAL BODY OF EXPERIMENTAL DATA, WE PROPOSE TO ENGAGE IN RESEARCH TO MEET FOUR COMPLEMENTARY OBJECTIVES: 1) ASSESSING THE SPECIFICITY OF CYTOCHROME P450-DEPENDENT MONOOXYGENASES FOR THE FORMATION OF MONOTERPENE ALCOHOLS AND EPOXIDES; 2) INVESTIGATING THE SPECIFICITY OF (-)-TRANS-ISOPIPERITENOL DEHYDROGENASES FOR DIVERSE MONOTERPENE ALCOHOLS AS SUBSTRATES; 3) EVALUATING THE SPECIFICITY OF (+)-PULEGONE REDUCTASES FOR UNSATURATED MONOTERPENE KETONES AS SUBSTRATES; AND 4) DEMONSTRATING TRANSLATIONAL CAPABILITIES USING KNOWLEDGE-BASED APPROACHES FOR BREEDING MINTS ACCUMULATING SPECIALTY OILS. THE PROPOSED ACTIVITIES WILL INFORM BREEDING EFFORTS AIMED AT DEVELOPING MINT CULTIVARS WITH ENHANCED AGRONOMIC TRAITS, BUT ALSO HAVE BROADER IMPLICATIONS FOR POLYPLOID ESSENTIAL OIL PLANTS IN GENERAL.