THE GOAL OF THE PROPOSED PROJECT IS TO IMPROVE COLD TOLERANCE IN SORGHUM BICOLOR BY (1) QUANTITATIVELY MEASURING BASAL AND ACCLIMATED COLD TOLERANCE AND UNCOVERING THE GENETIC BASIS COLD TOLERANCE AND (2) BY EXPLORING CROSSTALK BETWEEN THE PLANT HORMONE ABSCISIC ACID (ABA) SIGNALING AND COLD ACCLIMATION SIGNALING. SORGHUM BICOLOR (SORGHUM) IS AN IMPORTANT STAPLE CEREAL AND FORAGE CROP IN FOOD-LIMITED AREAS OF THE WORLD AND A PROMISING BIOFUEL FEEDSTOCK IN THE UNITED STATES. IT IS KNOWN FOR ITS DROUGHT AND HEAT RESILIENCE, BUT OVERALL SORGHUM YIELD IS LIMITED BY ITS SENSITIVITY TO COLD TEMPERATURES. COLD ACCLIMATION IS A PROCESS BY WHICH PLANTS ARE BETTER ABLE TO SURVIVE COLD TEMPERATURES AFTER EXPOSURE TO NON-LETHAL LOW TEMPERATURES. SINCE COLD ACCLIMATION HAS NOT PREVIOUSLY BEEN EVALUATED IN THE SORGHUM, THIS STUDY WILL QUANTITATIVELY MEASURE BASAL AND ACCLIMATED COLD TOLERANCE OF A SORGHUM POPULATION DESIGNED TO STUDY COLD TOLERANCE AND IDENTIFY GENOME REGIONS ASSOCIATED WITH VARIATION IN COLD TOLERANCE. EVIDENCE FROM OTHER PLANT SPECIES SUGGESTS THAT TREATMENT WITH THE PLANT HORMONE ABA IMPROVES COLD TOLERANCE, SO THIS STUDY WILL ALSO EVALUATE THE ABILITY OF ABA APPLICATION TO IMPROVE COLD TOLERANCE OF SORGHUM AND ANALYZE THE GENE EXPRESSION OF ABA- AND COLD-TREATED SEEDLINGS TO UNCOVER INTERSECTIONS BETWEEN THE TWO SIGNALING PATHWAYS. UNDERSTANDING VARIATION IN COLD TOLERANCE AMONG SORGHUM GENOTYPES WILL FURTHER EFFORTS TO BREED SORGHUM THAT IS MORE RESILIENT TO COLD TEMPERATURES AND EXPAND THE RANGE THAT SORGHUM CAN BE PLANTED IN AND ULTIMATELY INCREASE SORGHUM YIELDS.