**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** SORGHUM IS THE FIFTH MOST PRODUCED GRAIN CROP, AND THE U.S. IS THE LARGEST PRODUCER IN THE WORLD. DUE TO ITS RESILIENCE TO ABIOTIC STRESSES AND MARGINAL SOILS, SORGHUM IS EMERGING AS A PROMISING FOOD, FEED, AND BIOFUEL CROP ADAPTED TO LOW-INPUT CONDITIONS. AT PRESENT, HYBRID SORGHUM BREEDING RELIES ENTIRELY ON THE CYTOPLASMIC MALE STERILITY (CMS)-BASED THREE-LINE SYSTEM. NOT ONLY IS THE CMS SYSTEM COMPLICATED AND EXPENSIVE IN PRODUCING HYBRIDS, BUT ALSO IT LIMITS THE EFFICIENT EXPLORATION OF DIVERSE GERMPLASM RESOURCES FOR DEVELOPING ALL TYPES OF COMMERCIALLY DESIRED HYBRIDS. NUCLEAR MALE STERILITY (NMS)-BASED TWO-LINE SYSTEMS IN RICE AND MAIZE HAVE BEEN SHOWN TO BE EQUAL OR MORE EFFECTIVE AT CAPTURING HETEROSIS AS CONVENTIONAL SYSTEMS; HOWEVER, NO SUCH SYSTEM HAS BEEN DEVELOPED OR TESTED IN SORGHUM. IN THE TWO-LINE BREEDING SYSTEM, HYBRID SEEDS ARE PRODUCED BETWEEN A MALE-STERILE SEED PARENT AND A MALE-FERTILE POLLEN PARENT. IN HYBRID MAIZE BREEDING, MAIZE PLANTS PRODUCE SEPARATE MALE AND FEMALE INFLORESCENCES; THEREFORE, THE COMPLETE MALE STERILE LINES CAN BE ACHIEVED BY PHYSICALLY REMOVING TASSELS. IN RICE, CONDITIONAL MALE STERILE LINES ARE USED TO GENERATE MALE STERILE PLANTS FOR HYBRID SEED PRODUCTION UNDER THE RESTRICTIVE ENVIRONMENTAL CONDITION, AND TO MAINTAIN THEMSELVES UNDER THE PERMISSIVE ENVIRONMENTAL CONDITION. SORGHUM PLANTS PRODUCE BISEXUAL FLOWERS AND SORGHUM CONDITIONAL MALE STERILE LINES ARE NOT FOUND. THUS, THE GOAL OF THIS PROJECT IS TO DEVELOP THE BRIDGE PLANT WHICH CAN BE USED FOR TWO-LINE HYBRID BREEDING IN SORGHUM. RECENTLY, WE IDENTIFIED A STABLE AND EASILY RECOGNIZABLE SORGHUM MALE STERILE MUTANT MS8, WHICH IS DEFECTIVE IN ANTHER DEVELOPMENT AND CONSEQUENTLY FAILS TO PRODUCE POLLEN. WE THEN CLONED THE CAUSAL GENE MS8 FROM THE MS8 MUTANT. WE WILL MAKE THE BRIDGE PLANT BY GENETICALLY INTRODUCING A CONSTRUCT CONTAINING THREE TRANSGENES INTO THE MS8 MUTANT BACKGROUND. THE BRIDGE PLANT CAN PRODUCE 100% PURE TRANSGENE-FREE MALE STERILE PLANTS WHICH WILL SERVE AS FEMALE PARENTS TO BE POLLINATED WITH VARIOUS ELITE LINES FOR EFFICIENTLY BREEDING DESIRED HYBRIDS IN SORGHUM. IN ADDITION, THIS SYSTEM CAN MAINTAIN ITSELF FROM SELF-POLLINATION. IF SUCCESSFUL, THE OUTCOME OF THIS PROJECT SYSTEM WILL ACCELERATE BREEDING EFFICIENCY IN SORGHUM BY SIMPLIFYING AND EXPEDITING SORGHUM BREEDING PROCESS, AND BY BROADENING THE SPECTRUM OF HYBRID COMBINATIONS THAT CAN BE RAPIDLY EVALUATED. SUCH A SYSTEM WOULD HELP SORGHUM BREEDERS ACHIEVE BETTER GENETIC GAINS AND COULD POTENTIALLY PROTECT THE U.S. SORGHUM CROP FROM DEVASTATING DISEASES. THEREFORE, OUR PROJECT WILL ADDRESS CRITICALLY NEEDED AGRICULTURAL ISSUES. THE PROPOSED PROJECT WILL ALSO PROVIDE VALUABLE OPPORTUNITIES TO INCORPORATE RESEARCH INTO EDUCATIONAL ACTIVITIES IN PLANT BIOLOGY VIA INTEGRATING THE PROPOSED RESEARCH WITH TRAINING OF UNDERGRADUATE STUDENTS AND PROMOTING SCIENCE EDUCATION FOR HIGH SCHOOL STUDENTS.