**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 (SORGHUM BICOLOR), ARGUABLY THE WORLD'S MOST IMPORTANT MULTI-PURPOSE MONOCOT CROP GROWN FOR FOOD, FEED, AND/OR FUEL, SUFFERS SEVERE YIELD LOSSES DUE TO ATTACK BY PHLOEM-FEEDING INSECTS THAT LIMIT PLANT PRODUCTIVITY BY REMOVING PHLOEM SAP, ALTERING SOURCE-SINK PATTERNS, AND VECTORING PLANT VIRUSES. LIGNIN, AN ORGANIC POLYMER COMPOUND PRESENT IN NEARLY ALL PLANT SECONDARY CELL WALLS, PLAYS A CRITICAL ROLE IN PROTECTING PLANTS FROM BIOTIC STRESSES. HOWEVER, LITTLE IS KNOWN ABOUT HOW LIGNIN MODIFICATIONS IN SORGHUM WILL AFFECT PLANT PROTECTION AGAINST SUGARCANE APHID (SCA; MELANAPHIS SACCHARI), A CRITICAL PEST THROUGHOUT THE SORGHUM PRODUCTION REGIONS OF THE U.S. THE GOAL OF THIS PROPOSAL IS TO IMPROVE OUR UNDERSTANDING OF THE ROLE OF THE MONOLIGNOL PATHWAY, WHICH LEADS TO THE SYNTHESIS OF LIGNIN, IN SORGHUM DEFENSE AGAINST SCA.