**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 RESEARCHAIMS TO GENERATE KNOWLEDGE AND TOOLS TO BETTER BREED APPLES WITH RESISTANCE TO THE DESTRUCTIVE BACTERIAL DISEASE, FIRE BLIGHT. THE FOCUS IS ONTHE PRIMARY PROGENITOR OFDOMESTICATED APPLES,M. SIEVERSII.THIS WILD SPECIES HAS MODERATELY SIZED APPLESAND GENOTYPES WITH STRONG FIRE BLIGHT RESISTANCE THAT CAN BE USED DEVELOP FIRE BLIGHTRESISTANT APPLE CULTIVARSIN LESS GENERATIONS.TO ACHIEVE THIS,WE AIM TOFINEMAPA PREVIOUSLY IDENTIFIED MODERATE EFFECT FIRE BLIGHT RESISTANCE ALLELE, MSV_FB7. A LARGE GENETIC MAPPING POPULATION, ARTIFICIAL FIRE BLIGHT INOCULATIONS AND ADENSE PANEL OF GENETIC MARKERS WILL ENABLEAMORE PRECISECHARACTERIZATIONTHE LOCATION OF MSV_FB7. LOW-COST MARKERS WILL THEN BE DEVELOPED WITH THAT KNOWLEDGE TO ALLOW APPLE BREEDERS TO UTILIZE THAT SOURCE OF GENETIC RESISTANCE IN BREEDING PROGRAMS. ADDITIONALLY, THREE GENETIC MAPPING POPULATIONS MADE FROM CROSSINGA HIGHLY SUSCEPTIBLE APPLE CULTIVARWITH SEVERAL FIRE BLIGHT RESISTANTM. SIEVERSIIGENOTYPES WILL BE USED TO IDENTIFYGENETIC REGIONS WITHFIRE BLIGHT RESISTANCE ALLELES. THE OFFSPRINGOF THESE CROSSES WILL BE SCREENED WITH A PREVIOUSLY DEVELOPED FIRE BLIGHT LEAF DISC ASSAYTO RAPIDLY FIND THE MOST RESISTANT AND SUSCEPTIBLE INDIVIDUALS AT THE SEEDLING STAGE.THEN, SEVERAL OF THE MOST RESISTANTAND SUSEPTIBLE INDIVIDUALS WILL BE SEPARATELY POOLEDFORDNA AND RNA SEQUENCING TO IDENTIFY THE GENETIC BASIS OF FIRE BLIGHT RESISTANCE IN THESE PLANTS. THE RESULTS OF THESE PROJECTSCANBE USED TO DEVELOP NEW APPLE CULTIVARS WITHFIRE BLIGHT RESISTANCE THAT ARE LESS RESOURCE INTESIVE TO MANAGE.