ASA Oral Presentation Abstract- Trent Tate University of Georgia Griffin Campus Institute of Plant Breeding, Genetics and Genomics Dr. Melanie Harrison-Dunn Dr. Paul Raymer Molecular Survey of Turfgrass Species for Mutations Conferring Resistance to ACCase Inhibiting Herbicides. The control of grassy weeds in turfgrass is often problematic due to lack of herbicide selectivity. Seven different naturally occurring mutation sites have been reported to confer resistance to Acetyl coenzyme A carboxylase inhibiting herbicides. One or more of these mutation sites may hold potential as the basis for an herbicide resistant system for use in turf. Mutations conferring the resistance to this class of herbicides have been molecularly characterized, but most species of turfgrass have not been surveyed for the presence of these mutations. All mutation sites are within a 315 amino acid region of the carboxyl transferase domain of ACCase and are believe to impact binding affinity of ACCase inhibiting herbicides. The objective of this research was to sequence this region of ACCase and determine if resistance conferring mutations were present in eight warm-season, eight cool-season, and eight weedy grass species. All turfgrass species included both wild material from UDSA germplasm collection as well as released cultivars. DNA was extracted using a modified CTAB method. DNA primers flanking known mutation sites were used to amplify these regions using PCR. After band verification, remaining PCR products were purified and sent to Genewiz for Sanger sequencing. Sequence data was analyzed using Geneious software. Mutations were found at the 1781 aa position in Festuca ovina and Festuca rubra indicating that they should be highly resistant to sethoxydim and perhaps other ACCase inhibiting herbicides. Poa annua also contained a different mutation at the 1781 aa position indicating that its control by ACCase inhibiting herbicides would be ineffective. These results will be useful in designing an ACCase-based herbicide resistant system for multiple turfgrass species.