ARSENIC ACCUMULATION IN RICE POSES A SERIOUS THREAT TO AGRICULTURE AND HUMAN HEALTH IN THE U.S. AND WORLDWIDE. RICE IS A STAPLE CROP THAT FEEDS BILLIONS AND IS FREQUENTLY GROWN ON ARSENIC-CONTAMINATED LANDS, WHICH REDUCES CROP YIELDS AND EXPOSES CONSUMERS TO THE TOXIC EFFECTS OF ARSENIC THROUGH CONSUMPTION OF ARSENIC-LADEN RICE GRAIN. HENCE, THERE IS AN URGENT NEED TO DEVELOP RICE VARIETIES THAT LIMIT ARSENIC ACCUMULATION. THE GOAL OF THIS PROJECT IS TO IDENTIFY THE GENETIC FACTORS THAT CONTROL ARSENIC ACCUMULATION IN RICE GRAIN AND ARSENIC TOLERANCE OF RICE PLANTS. TO UNCOVER THESE FACTORS, WE WILL (1) GENERATE SEGREGATING POPULATIONS FROM CROSSES BETWEEN RICE CULTIVARS KNOWN FOR GRAIN-ARSENIC ACCUMULATION AND EXCLUSION, (2) IDENTIFY AND USE MOLECULAR MARKERS TO DISCOVER GENETIC FACTORS LINKED TO ARSENIC-RELATED TRAITS, AND (3) TEST THE IMPACT OF MANIPULATING THE EXPRESSION OF THESE FACTORS ON ARSENIC ACCUMULATION AND TOLERANCE. OUR RESULTS WILL FACILITATE BREEDING OF RICE CULTIVARS WITH INCREASED YIELDS AND DECREASED CONCENTRATION OF ARSENIC IN THE GRAINS. THIS WILL NOT ONLY RESULT IN ENHANCED RICE PRODUCTIVITY, DIRECTLY BENEFITING U.S. AND GLOBAL AGRICULTURE, BUT WILL ALSO DECREASE CONSUMPTION OF ARSENIC-CONTAMINATED RICE, WHICH IS INCREASINGLY RECOGNIZED AS A GLOBAL HEALTH CONCERN. THE PROPOSED PROJECT ADDRESSES THE FY 2016 PROGRAM AREA PRIORITY, PHYSIOLOGY OF AGRICULTURAL PLANTS, IN SEVERAL WAYS, AS IT EMPLOYS MOLECULAR AND WHOLE-PLANT APPROACHES TO 1) UNDERSTAND HOW PLANT GROWTH AFFECTS PRODUCTIVITY, 2) IMPROVE GRAIN NUTRITIONAL QUALITY, AND 3) UNDERSTAND MECHANISMS OF PLANT RESPONSES TO ABIOTIC STRESS.