Abstract

herbicides to mitigate its numerous ecological and economic impacts. Previous research has demonstrated that while many genotypes are sensitive to herbicides, some genotypes exhibit resistance. However, the mechanism(s) underlying herbicide resistance is unknown. Understanding mechanisms for resistance would benefit the development of alternative management strategies for sensitive versus resistant populations, and reduce economic and environmental costs associated with poor management responses. One hypothesis for herbicide resistance is that resistant genotypes harbor microbial communities that block the uptake and/or metabolize herbicide, leading to reduced herbicide efficacy. To test this hypothesis, we compared the microbial communities associated with four different genotypes known to exhibit different susceptibilities to the commonlyused herbicide 2,4Dichlorophenoxyacetic acid (2,4D). Using a controlled laboratory study, we exposed three ramets (vegetatively propagated clones) of each genotype to 500 μg L1 2,4D for 48 hours, and compared them to three control ramets that were not exposed to 2,4D. Microbial DNA were extracted from the roots and shoots of these plants. We will determine microbial composition from these extracts using 16S DNA barcoding using nextgeneration sequencing. We will use these data to determine whether sensitive and resistant genotypes have predictably distinct microbial communities that may be associated with variation in herbicide sensitivity.