Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/12/2016
Publication Date: 7/12/2016
Citation: Kesoju, S.R., Greene, S.L., Martin, R.C., Kramer, M.H. 2016. Pollen and seed mediated gene flow in commercial alfalfa seed production fields. Meeting Abstract. North American Alfalfa Improvement Conference, Madison, WI. July 12-14, 2016.
Interpretive Summary: Alfalfa is pollinated by bees and there are concerns that bees can inadvertently move genetically-engineered alfalfa pollen into fields that are conventional. Non genetically-engineered alfalfa hay and seed needs to remain uncontaminated since export and organic markets have low tolerance for genetically-engineered traits. But we lack information based on landscape-scale, commercial field level situations, on how far we need to separate fields in order to control the adventitious presence of genetically-engineered traits. Therefore our objective was to examine how far bees were moving pollen in a real life situation. In spring 2013, alfalfa seed and hay fields were mapped in the Touchet Valley, Walla Walla County, WA. Genetically engineered seed fields (source fields) and 14 conventional seed fields (sink fields), located at various distances from each other. We found that fields needed to be separated by 330 m to ensure that adventitious presence was below 0.9%, while 2441 m was needed to keep adventitious presence to below 0.1% level, which is considered by industry to be a non-detectable level. We found that variables such as slope, number of bees in conventional fields, and presence of alkali bees influenced isolation distances as well. This information will be useful to the alfalfa industry as they work to strengthen coexistence among alfalfa producers serving different markets.
Technical Abstract: The potential for gene flow has been widely recognized since alfalfa is pollinated by bees. The Western US is a major exporter of alfalfa seed and hay and the organic dairy industry is one of the fastest growing agricultural sectors. 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 transgene movement from GE seed fields to conventional seed fields on a landscape level based on the spatial distribution of commercial seed fields and to provide industry with information to support coexistence strategies. In spring 2013, alfalfa seed and hay fields were mapped in the Touchet Valley, Walla Walla County, WA. GE seed fields (source fields) and 14 conventional seed fields (sink fields), located at various distances from GE sources, were identified. Sink fields were harvested along field edges every 30 m and within fields for every 15 m. For constructing a predictive equation, the % AP was transformed to the logit scale. The relationship between AP proportion and distance to source fields at 0.1%, 0.5%, and 0.9% AP threshold levels were modeled using a quadratic regression. Though AP was detected in the original seed lots used to plant the sink seed fields sampled, the levels were within the company standards of threshold level 0.9% AP. If the distance from the source seed field is 330 m, about 95% of the samples will be below 0.9% detectable level while at 2441 m, 95% of the samples will be below 0.1% detectable level. Since we sampled field edges, overall field AP would likely be lower than our established thresholds. With increase in distance from GE seed field and distance from domiciles in GE seed field, the AP proportion decreased. Number of domiciles in conventional seed fields was negatively correlated with AP proportion while slope and distance from alkali bee beds were positively correlated.