**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BACTERIAL SPOT CAUSED BY XANTHOMONAS ARBORICOLA PV. PRUNI (XAP, A GRAM-NEGATIVE BACTERIUM) IS A MAJOR DISEASE OF PEACH AND OTHER STONE FRUITS. IN THE SOUTHEAST, PEACH GROWERS ROUTINELY SPRAY COPPER AND ANTIBIOTICS (OXYTETRACYCLINE) THROUGHOUT THE GROWING SEASON TO MANAGE BACTERIAL SPOT, BUT ANNUAL LOSSES OF OVER $20 MILLION WERE STILL REPORTED IN YEARS WITH HEAVY DISEASE PRESSURE IN SOUTH CAROLINA AND GEORGIA ALONE. TO MAKE MATTERS WORSE, ANTIBIOTICS-RESISTANT AND COPPER-TOLERANT XAP STRAINS HAVE RECENTLY EMERGED IN SOUTH CAROLINA PEACH ORCHARDS, WHICH WILL THREATEN TO REDUCE THE EFFICACY OF THE FEW CHEMICALS WE DO HAVE TO MANAGE BACTERIAL SPOT. THERE ARE MNAY UNKNOWNS THAT MUST BE ANSWERED TO IMPROVE DISEASE MANAGEMENT STRATEGIES.SPECIFICALLY, WHAT ARE THE MECHANISMS OF ANTIBIOTICS RESISTANCE AND COPPER TOLERANCE IN THE BACTERIAL PATHOGEN? ARE THE EMERGENCE AND PREVALENCE OF THESE RESISTANT/TOLERANT XAP STRAINS AFFECTED BY DIFFERENT CHEMICAL SPRAY PROGRAMS IN THE ORCHARDS? CONSIDERING THE DECREASE IN COPPER DOSAGE AS THE SEASON PROGRESSES FOR BACTERIAL SPOT CONTROL, AT WHAT POINT ARE COPPER SPRAY NO LONGER EFFECTIVE AGAINST THE COPPER TOLERANT XAP? DO RESISTANT/TOLERANT BACTERIAL PATHOGENS OVERWINTER ON PEACH TREES AND CONTRIBUTE TO THE DISEASE DEVELOPMENT IN THE FOLLOWING SEASON? WHICH ENVIRONMENTAL FACTORS AFFECT OVERWINTER SURVIVAL OF XAP? IF THE RESISTANT/TOLERANT XAP DO PERSIST AND SPREAD, WHAT WILL BE THE NEW OPTIONS FOR DISEASE CONTROL?GIVEN THE SIGNIFICANT IMPACT OF XAP ON THE PEACH INDUSTRY, WE PROPOSE TO INVESTIGATE THE QUESTIONS ABOVE TO BETTER UNDERSTAND ANTIBIOTICS RESISTANCE AND COPPER TOLERANCE IN XAP AND DEVELOP STRATEGIES TO MITIGATE RESISTANCE AND IMPROVE DISEASE CONTROL. THE FIRST OBJECTIVE OF THIS PROPOSAL IS TO EVALUATE HOW DIFFERENT SPRAY PROGRAMS IN DIFFERENT SOUTHEASTERN ORCHARDS IMPACT THE PREVALENCE OF ANTIBIOTICS RESISTANCE AND COPPER TOLERANCE IN XAP, AS WELL AS HOW THE RESISTANT/TOLERANT XAP AFFECT THE CURRENT CHEMICAL CONTROL PROGRAMS. THE SECOND OBJECTIVE IS TO IDENTIFY THE GENES CONFERRING ANTIBIOTICS RESISTANCE AND COPPER TOLERANCE IN XAP. THIS WILL NOT ONLY HELP US UNDERSTAND THE RESISTANCE/TOLERANCE MECHANISMS, BUT THE RESISTANCE GENES IN XAP WILL BE USED AS MARKERS TO DEVELOP MOLECULARDETECTION TOOLS FOR HIGH-THROUGHPUT MONITORING OF CHEMICAL RESISTANCE IN XAP POPULATIONS IN WHICH RESULTS COULD BEUTILIZED TO TAILOR SPRAY PROGRAMS IN REAL TIME.THE THIRD OBJECTIVE IS TO EVALUATE NOVEL CHEMICALS WITH DEMONSTRATED EFFICACY AGAINST XANTHOMONAS PATHOGENS OF OTHER CROPS FOR THEIR ABILITY TO CONTROL BACTERIAL SPOT OF PEACH WITH THE PRESENCE OF ANTIBIOTICS-RESISTANT AND COPPER-TOLERANT STRAINS. THESE NOVEL CHEMICALS COULD SERVE AS NEW OPTIONS FOR CONTROLLING XAP. THE FOURTH OBJECTIVE IS TO STUDY THE OVERWINTERING CAPABILITY OF XAP AND DEVELOP AN EPIDEMIOLOGICAL MODEL BASED ON ENVIRONMENTAL FACTORS DURING THE DORMANT SEASON TO PREDICT THE INOCULUM LEVELS FOR THE SUBSEQUENT GROWING SEASON. THIS MODEL WILL BE COMPLEMENTARY TO THE PREDICTION MODELS RECENTLY DEVELOPED FOR BACTERIAL SPOT DISEASE DEVELOPMENT, AND CAN LIKELY BE COMBINED TO FORM A DISEASE FORCASTING SYSTEMFOR THE GROWERS IN THE FUTURE.THE NOVEL CHEMICALS IDENTIFIED IN THE THIRD OBJECTIVE WILL BE TESTED FOR THEIR EFFECT ON REDUCING THE INOCULUM ON DORMANT TREES AS WELL.THE RESULTS FROM THIS PROJECT WILL CONTRIBUTE TO THE FUTURE DEVELOPMENT OF A SUSTAINABLE AND ENVIRONMENTALLY FRIENDLY DISEASE MANAGEMENT PROGRAM WITH HIGHER EFFICACY TO REDUCE XAP INOCULUM AND MINIMIZE DISEASE DEVELOPMENT, WHICH WILL THEN CONTRIBUTE TO LOWER DISEASE INCIDENCE, HIGHER FRUIT YIELD, AND HIGHER RETURNS FOR THE GROWERS. THIS PROJECT WILL BENEFIT PEACH AND OTHER STONE FRUIT GROWERS IN THE 22 STATES THAT CONTEND WITH BACTERIAL SPOT, AND ESPECIALLY IN THE SEVEN STATES WHERE THIS DISEASE IS IDENTIFIED AS A STAKEHOLDER IPM PRIORITY. THIS PROJECT WILL CONTRIBUTE TO POTENTIAL LONG-RANGE IMPROVEMENT IN SUSTAINABILITY OF U.S. AGRICULTURE AND FOOD SYSTEMS BY SUSTAINING THE ECONOMIC VIABILITY OF PEACH AND OTHER STONE FRUIT PRODUCTION, SATISFYING HUMAN FOOD NEEDS, AND ENHANCING THE QUALITY OF LIFE FOR FARMERS AND SOCIETY AS A WHOLE.