**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THIS STANDARD RESEARCH PROPOSAL UTILIZES NATURALLY-OCCURRING VARIATION TO IMPROVE FIBER FINENESS IN ONE OF THE MOST ECONOMICALLY IMPORTANT AND GENETICALLY VULNERABLE US CROPS, COTTON. IN PRELIMINARY WORK WITH THE SALIENT COMMODITY BOARD, WE PRODUCED A 'NESTED ASSOCIATION MAPPING' RESOURCE FOR EXOTIC COTTONS SELECTED FOR RACIAL, GEOGRAPHIC AND SSR DIVERSITY.FOLLOWING EXPLORATORY PHENOTYPIC EVALUATION, WE GENETICALLY MAPPED POPULATIONS RANKING #1, 3, AND 29 (OF 31) IN A SELECTION INDEX THAT EQUALLY WEIGHTED LOW MICRONAIRE AND HIGH FIBER STRENGTH (THE LATTER TO PRECLUDE FIBER IMMATURITY). HERE, WE PROPOSE TO PHENOTYPE AND GENOTYPE POPULATIONS RANKING #2, 4, AND 6 - COLLECTIVELY COVERING THE FOUR BEST FOR FIBER FINENESS AND SAMPLING ADDITIONAL DESIRABLE TRAITS.A NOVEL ELEMENT IS THE USE OF COSTLY 'AFIS' TECHNOLOGY, MITIGATING LIMITATIONS OF THE CURRENT STANDARD 'HVI' TESTING OF FIBER FINENESS. IDENTIFICATION OF DIAGNOSTIC DNA MARKERS WILL FACILITATE TRANSFER OF FIBER FINENESS ALLELES INTO ELITE CULTIVARS, MINIMIZING THE NEED FOR TESTING LARGE NUMBERS OF SAMPLES TO SELECT BASED ON EITHER HVI OR AFIS-BASED FIBER QUALITY.SEVERAL GENETIC HYPOTHESES WILL BE TESTED, ALSO PRODUCING A WELL-GROOMED SET OF POPULATIONS FOR FURTHER STUDYPARTNERSHIP BETWEEN A PLANT BREEDER AND A GENOME BIOLOGIST WILL INTEGRATE TRAINING IN FIELD-BASED BREEDING WITH EFFECTIVE UTILIZATION OF GENOMICS.