**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE COTTON LEAFROLL DWARF VIRUS, WHICH CAUSES COTTON BLUE DISEASE (CBD), IS REGARDED AS THE SECOND MOST DAMAGING VIRAL DISEASE TO COMMERCIAL COTTON WORLDWIDE. THE RECENT DISCOVERY OF CLRDV IN THE U.S. INDICATES THIS VIRUS MAY POSE A SIGNIFICANT THREAT TO THE PROFITABILITY OF COTTON PRODUCTION. IDENTIFYING DURABLE SOURCES OF GENETIC RESISTANCE AND THE UNDERLYING MECHANISMS THAT CONTRIBUTE TO THE TRAIT IS AN IMPORTANT STEP IN THE DEVELOPMENT OF RESISTANT VARIETIES. IN THIS PROPOSED RESEARCH, A TEAM OF SCIENTISTS, WHICH INCLUDE A BREEDER (KOEBERNICK), GENETICIST (CHEE), AND VIROLOGIST (BAG) WITH COMPLEMENTARY SKILL SETS, WILL WORK CLOSELY WITH AN ENGAGED STAKEHOLDER (JONES) TO UNDERTAKE ACTIVITIES SALIENT TO GERMPLASM EVALUATION AND PRE-BREEDING FOR CLRDV RESISTANCE, AND TO THE DEVELOPMENT AND APPLICATION OF TOOLS TO PREDICT PHENOTYPE FROM GENOTYPE TO ACCELERATE BREEDING OF CLRDV RESISTANT CULTIVARS. THE SPECIFIC OBJECTIVES OF THIS PROJECT ARE TO: 1)IDENTIFY SOURCES OF RESISTANCE TO CLRDV IN UPLAND COTTON, 2) GENETIC MAPPING TO IDENTIFY DIAGNOSTIC MARKERS FOR THE RESISTANT GENE(S), AND 3) ELUCIDATE AND CHARACTERIZE PUTATIVE DEFENSE GENES AGAINST THE REDDENING AND LEAF DOWNWARD CUPPING SYMPTOMS THAT ARE COMMONLY ASSOCIATED WITH CLRDV. WE EXPECT THIS PROJECT TO UNCOVER NEW SCIENTIFIC KNOWLEDGE AND GENETIC RESOURCES FOR GENETIC IMPROVEMENTS OF HOST PLANT-RESISTANCE FOR THIS EMERGING VIRAL DISEASE. THIS PROPOSAL IS SUBMITTED IN RESPONSE TO AND SUPPORTED BY THE COTTON BOARD AND AIMS TO DEVELOP AND DEPLOY GERMPLASM, GENETIC, AND MOLECULAR TOOLS FOR RESISTANCE TO CLRDV.