** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BACKGROUND: EXPANSION OF THE US EASTERN OYSTER AQUACULTURE INDUSTRY DEPENDS ON EFFECTIVE CONTROL OF DISEASE ORGANISMS ENCOUNTERED DURING OYSTER GROW-OUT. TWO PATHOGENS, CALLED DERMO AND MSX, ARE THE CAUSE OF OF SIGNIFICANT MORTALITY IN WILD AND AQUACULTURE OYSTERSIN THE MANY STATES ALONG THE EAST COASTAND BEYOND, AND AS SUCH, BETTER DISEASE-RESISTANT STOCKS ARE REQUIRED.GOALS: THE OVERALL GOAL OF THIS PROJECT IS TO DEVELOP A BETTER UNDERSTANDING OF THERELATIONSHIPS BETWEEN TWO SIGNIFICANT OYSTERPATHOGENS AND PERFORMANCE OF EASTERN OYSTERS GROWN IN THE FIELD DESTINED FOR HARVESTING AND SALE.SPECIFICALLY, AN ASSESSMENT OF THE HERITABILITY OF RESISTANCE TO EACH PATHOGEN SEPARATELY, OR COMBINED, WILL ENABLE THE DEVELOPMENT OF IMPROVED DISEASE-RESISTANCE BREEDING STRATEGIES.OBJECTIVES/METHODS: THE SPECIFIC OBJECTIVES OF THIS STUDY ARE TOMEASURE THE VARIANCE INSURVIVAL OF GENETICALLY-UNIQUE OYSTER GROUPS INFIELD TRIALS AT LOCATIONS WHERE THE TWO DISEASES ARE NATURALLY PRESENT IN THE ENVIRONMENT. UNIQUE GENETIC GROUPS OF OYSTERS WITH A KNOWNPEDIGREE WILL BE THE FOUNDATIONAL MATERIAL FOR THIS WORK. THE NUMBER OF OYSTERSTHAT GET INFECTED WITHIN EACH GROUP AS WELL AS HOW SEVERELY THEYARE INFECTED, INCLUDING THE SEVERITY OF THE HOSTRESPONSE, WILL BE STUDIED USING GENETIC TECHNIQUES AND TECHNIQUES THAT ALLOW MICROSCOPIC EXAMINIATION OF PRESERVED OYSTER TISSUES. THE RELATIONSHIP BETWEEN THE DIFFERENT GENETIC GROUPS (PEDIGREE INFORMATION), FIELD SURVIVAL, GROWTH AND DISEASE INFORMATION WILL BE COMBINED USING SOPHISTICATED MATHEMATICAL MODELING AND PREDICTIVE APPROACHES.THESE RESULTS WILL CLARIFY HOW THE DISEASES EFFECT OYSTER PERFORMANCE (CORRELATION VALUES) AND HOW EASILY IT IS TO BREED FOR RESISTANCE TO ONE OR BOTH PATHOGENS (HERITABILITY VALUES).OUTCOMES/IMPACTS: UPON COMPLETION OF THIS RESEARCH,THE AQUACULTURE GENETICS AND BREEDING TECHNOLOGY CENTER AT VIMS WILLCREATE NEW DISEASE-RESISTANT OYSTER STOCKS. THESE STOCKS WILL BE DISTRIBUTED TO TO REGIONAL COMMERCIAL HATCHERIES FOR PROPAGATION AND SALES OF OYSTER LARVAE AND SEED WITH SUPERIOR DISEASE RESISTANCE. IMPROVED OYSTER LINES WILL INCREASE THE SECURITY AND PROFITABILITY OF US OYSTER AQUACULTURE PRODUCTION.