** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** COTTON IS A MAJOR COMMERCIAL CROP IN THE SOUTHEASTERN UNITED STATES HOWEVER, THE WARM AND WET SUMMERTIME WEATHER IN THE REGION CAN CREATE FAVORABLE CONDITIONS FOR DISEASE DEVELOPMENT, CAUSING CHALLENGES FOR COTTON GROWERS. SPECIFICALLY, SEEDLING DISEASES CAN CAUSE DELAYED CROP DEVELOPMENT AND LOSS OF YIELD, UNIFORMITY, AND STAND, REQUIRING REPLANTING WHICH INCREASES INPUT COSTS FOR GROWERS. THE LONG-TERM GOALS OF THIS RESEARCH PROJECT ARE TO IMPROVE KNOWLEDGE ABOUT PATHOGEN ABUNDANCE AND FUNCTION ACROSS THE SOUTHEASTERN REGION AND TO IDENTIFY BENEFICIAL MICROORGANISMS THAT IMPROVE COTTON SEEDLING HEALTH AND GROWTH. THIS GOAL WILL BE ACCOMPLISHED THROUGH THREE OBJECTIVES: 1) CHARACTERIZATION OF PATHOGEN ABUNDANCE, 2) DETERMINING PATHOGEN FUNCTION ACROSS THE REGION, AND 3) IDENTIFICATION OF GROWTH-PROMOTING MICROORGANISMS SPECIFIC TO COTTON. A TARGETED SEQUENCING APPROACH (AMPLICON SEQUENCING) WILL DETERMINE THE PATHOGEN PRESENCE AND ABUNDANCEWHILE AN UNTARGETED SEQUENCING APPROACH (SHOTGUN SEQUENCING)WILL DETERMINE PATHOGEN FUNCTION ACROSS THE REGION.WHEN THESE SEQUENCE DATA ARE PAIRED WITH ENVIRONMENTAL AND SOIL VARIABLES, WE CAN UNCOVER REGIONAL OR ENVIRONMENTAL PATTERNS IN PATHOGEN ABUNDANCE AND FUNCTION. FURTHER, WE WILL USE THESE SEQUENCE DATA TO IDENTIFY PLANT-SELECTED MICROBES, CREATE SYNTHETIC COMMUNITIES USING THE IDENTIFIED MICROBES, AND TEST, VIA PLANT INOCULATIONS, IF THESE COMMUNITIES BENEFIT COTTON SEEDLING GROWTH AND HEALTH.THIS PROJECT IS DIRECTLY RELEVANT TO THE PROGRAM AREA 'AGRICULTURAL MICROBIOMES IN PLANT SYSTEMS AND NATURAL RESOURCES' BECAUSE THE PURPOSE OF THIS PROJECT IS TO CHARACTERIZE THE MICROORGANISMS PRESENT IN THE SOIL, RHIZOSPHERE, AND ROOTS OF COTTON SEEDLINGS, AN UNDERSTUDIED FIELD CROP, COLLECTED ACROSS THE SOUTHEASTERN US TO IDENTIFY PATTERNS OF PATHOGEN ABUNDANCE AND FUNCTION BY REGION OR ENVIRONMENTAL FACTOR.FINDINGS FROM THIS PROJECT WILL PROVIDE GEOGRAPHIC-SPECIFIC FOUNDATIONAL INFORMATION ABOUT THE SOIL AND PLANT-ASSOCIATED MICROBIOME THAT COTTON GROWERS CAN APPLY TO IMPROVE SEEDLING HEALTH AND YIELD. IT WILL ALSO REVEAL FOUNDATIONAL KNOWLEDGE ON THE DRIVERS OF SEEDLING PATHOGENS AND GROWTH PROMOTION THAT FUTURE STUDIES CAN USE AS THE BASIS FOR MECHANISTIC STUDIES OF HOW COMMUNITIES FORM AND FUNCTION.