Location: Water Quality and Ecology ResearchTitle: The herbicide glyphosate impacts rhizosphere soil exoenzyme activities and microbial community structure associated with glyphosate–tolerant and non-tolerant corn
Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/9/2013
Publication Date: N/A
Technical Abstract: Background Conservation tillage practices across the country have been implementing genetically engineered herbicide resistant crops along with applications of the herbicide glyphosate. We tested the hypothesis that five years of glyphosate applications to both resistant and non-resistant corn would impact key soil exoenzymes involved in mineralization and their associated soil microbial community. Method The experimental design for this conservation tillage study was a randomized complete block with glyphosate resistant (GR) and non-GR corn and with and without glyphosate applications. Bulk and rhizosphere soil samples from this study at the USDA-ARS Southern Weed Science Research Unit farm, Stoneville, MS were analyzed for three exoenzymes ß-glucosidade (BG), ß-N-acetylglucosaminidase (NAG), acid phosphatase (AP), and for fluorescein diacetate (FDA) hydrolysis as a measure of total microbial activity. DNA extracted from corn rhizosphere and adjacent bulk soils was prepared for analysis by denaturing gradient gel electrophesis (DGGE) profiling of 16sRNA genes from bacterial and archaeal components of both soil microbial communities. Results Differences (at P < 0.05) in mean AP, NAG, and FDA activities in rhizosphere soils were observed for treatments without glyphosate applications. No differences were observed for bulk soils. DGGE profiles indicated differences between treatments in both bacterial and archaeal communities. Sequencing of unique bands will have been performed. Conclusion Glyphosate applications appeared to decrease exoenzyme activity in rhizosphere soil of both GR and non-GR corn, and appeared to impact the associated rhizosphere soil microbial communities.