Skip to main content
ARS Home » Research » Publications at this Location » Publication #346685
Title: Isolation distances for transgenic alfalfa seed production in the Pacific Northwest

Author
item KESOJU, SANDYA - Columbia Basin College
item Greene, Stephanie
item Martin, Ruth
item Kramer, Matthew
item WALSH, DOUG - Washington State University
item Boydston, Rick

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2018
Publication Date: 4/25/2019
Citation: Kesoju, S., Greene, S.L., Martin, R.C., Kramer, M.H., Walsh, D., Boydston, R.A. 2019. Isolation distances for transgenic alfalfa seed production in the Pacific Northwest. Crop Science. 59(4):1701-1708. https://doi.org/10.2135/cropsci2018.07.0414.
DOI: https://doi.org/10.2135/cropsci2018.07.0414

Interpretive Summary: Alfalfa was the first perennial crop genetically-engineered (GE) to resist glyphosate-resistant herbicide and was initially deregulated in 2006, and again in 2011. Since alfalfa is largely insect-pollinated the potential for pollen-mediated gene flow has been widely recognized. The Western United States is the most important production area for both alfalfa forage and alfalfa seed. Because of this, many alfalfa producers are impacted by market sensitivity to adventitious-presence (AP) of GE traits. Our objective was to quantify the extent of gene movement from GE seed fields to commercial conventional seed fields on a landscape level and to define pollen dispersal distance to provide the industry with information to support coexistence strategies. We found that with increase in distance, pollen-mediated gene flow decreased. When threshold levels were set at 0.9% AP, the isolation distance needed between conventional and GE fields was 330 m to ensure at least 95% of the samples fell below the threshold level. When threshold levels were set at 0.5% and 0.1% AP, the isolation distance between conventional and GE field was 602 m and 2441 m, to ensure 95% of the samples fell below 0.5% and 0.1%. Knowing these distances will help producers make sound management decisions to ensure conventional seed is not negatively impacted by cross contamination from GE pollen.

Technical Abstract: Alfalfa was the first perennial crop genetically-engineered (GE) to resist glyphosate-resistant herbicide and was initially deregulated in 2006, and again in 2011. Since alfalfa is largely insect-pollinated the potential for pollen-mediated gene flow has been widely recognized. The Western United States is the most important production area for both alfalfa forage and alfalfa seed. Because of this, many alfalfa producers are impacted by market sensitivity to adventitious-presence (AP) of GE traits. Our objective was to quantify the extent of gene movement from GE seed fields to commercial conventional seed fields on a landscape level and to define pollen dispersal distance to provide the industry with information to support coexistence strategies. Alfalfa seed fields were mapped in the Touchet area, Walla Walla Valley, Washington during spring 2013. GE seed fields and 14 conventional seed fields, located at various distances from GE sources, were identified. Conventional seed fields were combine and hand harvested along field edges every 30 m and within fields and seed assessed for the presence of the CP4 5-enolpyruvylshikimate-3-phosate synthase (EPSPS) protein. for every 15 m. Using a quadratic regression, the relationship between AP proportion and distance to GE source fields at 0.1%, 0.5%, and 0.9% AP threshold levels were modeled. With the increase in distance, the pollen-mediated gene flow decreased. When threshold levels were set at 0.9% AP, the isolation distance needed between conventional and GE fields was 330 m to ensure at least 95% of the samples fell below the threshold level. When threshold levels were set at 0.5% and 0.1% AP, the isolation distance between conventional and GE field was 602 m and 2441 m, to ensure 95% of the samples fell below 0.5% and 0.1%. Since we sampled field edges, overall field AP would likely be lower than our established thresholds. Spatial prediction maps were consistent with our statistical analysis results. At an average distance of 2.2 km, AP was 0.05% and decreased to 0.03 at an average distance of 8.8 km from GE seed fields.