SALINITY IS A MAJOR CLIMATE-RELATED RISK FOR SUSTAINABLE RICE PRODUCTION. THE MAJOR OBSTACLE TO DESIGN SALT TOLERANT VARIETIES IS THE NARROW GENETIC BASE OF US RICE GERMPLASM. ALTHOUGH WE HAVE SUCCESSFULLY DEVELOPED SALT TOLERANT BREEDING LINES, THE LEVEL OF SALT TOLERANCE IN THESE LINES NEEDS FURTHER ENHANCEMENT. SINCE MULTIPLE MECHANISMS CONTRIBUTE TO SALT TOLERANCE AND FAVORABLE ALLELES ARE DISTRIBUTED AMONG VARIOUS DONORS, PYRAMIDING OF GENES FROM MULTIPLE DONORS IS NEEDED. THE OVERALL GOAL OF THIS PROPOSAL IS TO EXPLOIT THE NATURAL GENETIC VARIATION TO DEVELOP RICE CULTIVARS WITH ENHANCED SALT TOLERANCE. OUR SPECIFIC OBJECTIVES ARE: (A) PYRAMIDING OF FAVORABLE SALT TOLERANCE GENES FROM SELECTED DONOR GERMPLASM, AND (B) IDENTIFICATION OF SUPERIOR SALT TOLERANT ALLELES FROM MULTIPLE DONORS FOR RICE IMPROVEMENT. INTROGRESSION LINES DEVELOPED FROM MULTIPLE DONORS WILL BE UTILIZED FOR DEVELOPING SUPERIOR SALT TOLERANT LINES THROUGH PYRAMIDING. EVALUATION OF THESE LINES FOR SALT TOLERANCE AND AGRONOMIC PERFORMANCE IN GREENHOUSE AND FIELD EXPERIMENTS WILL BE DONE TO IDENTIFY HIGH YIELDING BREEDING LINES WITH ENHANCED SALT TOLERANCE. WHOLE GENOME AND TRANSCRIPTOME SEQUENCING OF PYRAMIDED LINES AND PARENTS WILL BE DONE TO IDENTIFY POTENTIAL SALT TOLERANT GENES AND THEIR SUPERIOR ALLELIC VARIANTS. THE PROJECT WILL GENERATE ADVANCED BREEDING LINES WITH ENHANCED SALT TOLERANCE AND GENOMIC RESOURCES FOR THE PUBLIC SECTOR BREEDING PROGRAM TO ACCELERATE DEVELOPMENT OF CLIMATE RESILIENT RICE VARIETIES AND ELUCIDATION OF THE MOLECULAR BASIS OF COMPLEX SALT TOLERANCE MECHANISMS OPERATING IN RICE.