**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 PROPOSAL IS AN INTERNATIONAL AND MULTISTATE COLLABORATION USING MODERN BIOTECHNOLOGY TOOLS TO HELP WITH ADVANCING ALLELES FOR RESISTANCE TO MAJOR PATHOGENS AND PESTS AFFECTING PEANUT PRODUCTION WORLDWIDE. WE WILL TRANSFER NOVEL WILD SPECIES ALLELES INTO A SET OF BACKCROSSED BREEDING LINES SHARING A COMMON, POPULAR GENETIC BACKGROUND (THE VARIETY FLORUNNER), AND EACH POSSESSING A SMALL SEGMENT OF CHROMOSOMAL DNA INHERITED FROM THE WILD SPECIES PARENTS. AS PART OF THIS EFFORT, WE WILL SCREEN THE INVOLVED BREEDING LINES FOR DISEASE AND PEST RESISTANCE, IDENTIFY DNA MARKERS DIAGNOSTIC FOR THESE RESISTANCES, AND IDENTIFY CANDIDATE GENES RESPONSIBLE FOR RESISTANCE. THE PRODUCT BREEDING LINES WILL BE AVAILABLE FOR MARKER-ASSISTED PYRAMIDING OF ALLELES INTO MULTIPLE DISEASE-RESISTANT CULTIVARS.OBJECTIVES OF THE PROJECT ARE:1. PERFORM HIGH-RESOLUTION SCORING OF A POPULATION FORMED FROM BACKCROSSING A WILD SPECIES-DERIVED PARENT BY A COMMON PEANUT CULTIVAR, AND IDENTIFY SINGLE-NUCLEOTIDE POLYMORPHISM DNA MARKERS TO DISTINGUISH THE ACCESSIONS AND THEIR CHROMOSOMES.2. MAKE BACKCROSSES TO THE CULTIVATED PARENT, AND USE DNA MARKERS TO SELECT ACCESSIONS WITH THE COMMON GENETIC BACKGROUND, AND ONLY DIFFERING BY A SMALL SEGMENT OF A CHROMOSOME THAT WAS INHERITED FROM ONE OF THE WILD SPECIES PARENTS. THIS SET OF ACCESSIONS, CALLED NEAR-ISOGENIC INTROGRESSION LINES, WILL BE RELEASED AS SEED AS A RESOURCE FOR BREEDERS AND OTHER SCIENTISTS TO USE IN THEIR WORK.3. SCORE PLANT MATERIALS FOR THE STRENGTH AND MECHANISMS OF RESISTANCE TO ROOT-KNOT NEMATODES, LEAF SPOTS, AND AFLATOXIN CONTAMINATION, AND IDENTIFY DNA MARKERS (CALLED QUANTITATIVE TRAIT LOCI, QTLS) LINKED TO DIFFERENT GENES FOR RESISTANCE.4. STUDY DIFFERENCES IN THE EXPRESSION OF GENES IN RESISTANT AND SUSCEPTIBLE MATERIALS, AND USE THESE RESULTS TO IDENTIFY GENES THAT MAY BE ASSOCIATED WITH RESISTANCE. 5. TEST THE QTL MARKERS FOUND IN THE BACKCROSSED LINES AFTER CROSSING TO OTHER VARIETIES, TO DETERMINE WHETHER THE SAME MARKERS CAN BE USED TO SELECT FOR RESISTANCE IN PLANT POPULATIONS MADE WITH OTHER PARENTS. THIS TESTING WILL BE DONE USING SELECTED BACKCROSS LINES AS DONOR PARENTS OF RESISTANCE, WITH RUNNER AND SPANISH VARIETIES AS THE SECOND PARENT. TESTING WILL BE PERFORMED IN THE US AND WEST AFRICA.6. PROVIDE EDUCATIONAL OPPORTUNITIES FOR GRADUATE AND UNDERGRADUATE STUDENTS IN NATURAL SCIENCES AND AGRICULTURE AT US UNIVERSITIES, INCLUDING A MINORITY-SERVING UNDERGRADUATE COLLEGE, AND IN UNIVERSITIES IN WEST AFRICA.