** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** RICE PRODUCTION IS IMPACTED BY BOTH DAYTIME AND NIGHTTIME HEAT STRESS. HOWEVER, HIGH NIGHTTIME TEMPERATURE (HNT) HAS A MORE DETRIMENTAL EFFECT ON RICE YIELD AND QUALITY AND IS CONSIDERED AN IMMEDIATE THREAT AS THE AVERAGE NIGHTTIME TEMPERATURE IS RISING RAPIDLY WORLDWIDE, INCLUDING IN THE U.S. SEVERAL STUDIES HAVE CATEGORICALLY LINKED HNT DURING REPRODUCTIVE STAGES TO LOW GRAIN YIELD AND QUALITY. THE NORMAL NIGHTTIME TEMPERATURE FOR THE RICE GROWING REGIONS IN THE U.S. IS CONSIDERED TO BE ~22 OC, BUT THE AVERAGE NIGHTTIME TEMPERATURE HAS BEEN INCREASING OVER THE LAST DECADES, ESPECIALLY IN CALIFORNIA AND ARKANSAS RICE GROWING REGIONS. THE HNT OF 28 OC DURING THE FLOWERING STAGE COULD LEAD TO SIGNIFICANT YIELD DECLINES AND HNT OF 32 OC IS DEVASTATING, RESULTING IN UP TO 90% LOSS IN THE GRAIN YIELD. SIGNIFICANT INCREASE IN PERCENTAGE CHALK WERE ALSO OBSERVED IN RICE GRAINS UNDER HNT. WHICH IS AN UNDESIRABLE CHARACTERSITICS THAT IMPACTS GRAIN APPEARANCE, COOKING QUALITY, AND PALATABILITY LEADING TO THE REDUCTION OF THE MARKET VALUE OF US RICE IN THE EXPORT MARKETOUR ULTIMATE GOAL IS TO PROVIDE PLANT BREEDERS AND RICE PRODUCERS IN THE U.S. A RICE GERMPLASM AND/OR VARIETY THAT IS TOLERANTT TO HNT PARTICULARLY ON TRAITS SUCH AS SPIKELET FERTILITY AND PERCENTAGE CHALK THAT INFLUENCES GRAIN YIELD AND QUALITY RESPECTIVELY. WE WILL IDENTIFY GENES OR QUANTITATIVE TRAIT LOCI (QTL) IN THE DNA OF US RICE GERMPLASM AS WELL AS N22, AN EXOTIC RICE THAT HAS A KNOWN TOLERANCE TO HNT USING GENOMEWIDE ASSOCIATION STUDIES (GWAS) AND QTL MAPPING APPROACH. WE WILL TAG THOSE IDENTIFIED GENES OR QTL AND DEVEOP DNA MARKERS. THESE DNA MARKERS FOR HNT TOLERANCE WILL BE USED IN THE BREEDING PROGRAM TO IDENTIFY LINES/VARIETIES THAT CAN BE TESTED AND ADVANCED IN THE BREEDING PIPELINE. THESE LINES WILL THEN BE SCREENED IN CONTROLLED GROWTH CHAMBER FOR HNT TOLERANCE AS WELL AS TESTED FOR ALL OTHER AGRONOMIC AND GRAIN QUALITY CHARACTERISTICSS ACROSS DIFFERENT LOCATIONS AND SEVERAL YEARS IN ARKANSAS BEFORE RELEASING AS A GERMPLASM AND/OR VARIETY. ADDITIONALY, OUR GENE EDITING APPRAOCH WILL HELP US UNDERSTAND THE MECHANISM ASSOCIATED WITH A WELL-KNOWN CHALK QTL AND COULD REVEAL PATHWAYS AND GENES CONTROLLING GRAIN YIELD AND CHALKINESS. THE TRANSCRIPTOMIC, PROTEOMIC, AND METABOLOMIC RESULTS WILL ALSO AID IN THE DEVELOPMENT OF HNT TOLERANT ELITE RICE LINES AND WILL CONTRIBUTE TO THE GENETIC RESOURCES THAT COULD BE USED IN PUBLIC BREEDING PROGRAMS OR RELEASED AS CULTIVARS, THESE DATASETS WILL BE MADE AVAILABLE TO THE RICE RESEARCH COMMUNITY THROUGH PUBLIC REPOSITORIES.