**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** TO REMAIN COMPETITIVE AND PROFITABLE, THE U.S. GREENHOUSE INDUSTRY MUST CONTINUALLY DEVELOP NEW TECHNOLOGIES THAT OPTIMIZE THE EFFICIENCY OF PRODUCTION AND IMPROVE CROP QUALITY WHILE REDUCING THEIR ENVIRONMENTAL IMPACT. THE RHIZOSPHERE IS THE AREA AROUND A PLANT'S ROOTS THAT IS INHABITED BY A UNIQUE POPULATION OF MICROORGANISMS (PRIMARILY FUNGI AND BACTERIA). THIS COLLECTION OF MICROBES IS CALLED THE MICROBIOME. THE MAKEUP OF THE MICROBIOME IN THE RHIZOSPHERE IS INFLUENCED BY THE HOST PLANT AND THE ENVIRONMENT. BACTERIA THAT CAN INHABIT AND COLONIZE THE PLANT RHIZOSPHERE AND PROVIDE BENEFITS TO PLANT GROWTH ARE CALLED PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) THE APPLICATION OF MICROBIAL INOCULANTS THAT INCLUDE THESE PGPR CAN INCREASE THE AVAILABILITY AND PLANT UPTAKE OF ESSENTIAL NUTRIENTS, THEREBY REDUCING NUTRIENT LEACHING AND ENVIRONMENTAL CONTAMINATION. MOST PGPR-CONTAINING PRODUCTS HAVE INCONSISTENT BENEFITS FOR GREENHOUSE CROPS BECAUSE THEY HAVE NOT BEEN TESTED OR OPTIMIZED FOR THE CONDITIONS THAT ARE UNIQUE TO CONTROLLED ENVIRONMENT AGRICULTURE. THE GOALS OF THIS PROPOSAL ARE TO IDENTIFY PGPR THAT BENEFIT CROP PERFORMANCE IN SOILLESS, CONTAINERIZED PRODUCTION SYSTEMS AND TO INVESTIGATE HOW THE RHIZOSPHERE MICROBIOME IS INFLUENCED BY COMMON GREENHOUSE PRACTICES. WE WILL IDENTIFY BACTERIA THAT CAN HELP PLANTS TAKE UP AND UTILIZE PHOSPHORUS AND IRON MORE EFFICIENTLY. GREENHOUSE EXPERIMENTS WILL BE CONDUCTED TO DETERMINE IF THESE BACTERIA IMPROVE THE GROWTH AND QUALITY OF VEGETABLE AND ORNAMENTAL BEDDING PLANTS. SYNTHETIC BACTERIAL COMMUNITIES THAT CAN INCREASE FERTILIZER USE EFFICIENCY AND IMPROVE CROP PERFORMANCE WILL BE CREATED. WE WILL EVALUATE THE INFLUENCE OF PH, NUTRIENT DEFICIENCY, MEDIA MOISTURE CONTENT, AND PLANT GROWTH RETARDANTS ON THE RHIZOSPHERE MICROBIOME COMMUNITY STRUCTURE.