Politics and Promiscuity In Vegetable Seed Production: The Unintended Consequences of Going Green

In Oregon’s Willamette Valley, vegetable seed production is estimated to be a 27 million dollar a year industry. Except under special permit from the Oregon Department of Agriculture, canola can only be grown in the Willamette Valley as a small scale seed crop, with larger acreage fields being relegated to specific rapeseed control districts outside of the valley. The combination of the need for rotational crops with grass seed production, and an increased desire for local biofuel production has created interest among growers to plant Brassica napus (canola) inside the valley. However, serious questions have arisen over the potential damage large scale canola production could have on the preexisting Brassica vegetable seed production. To address these concerns we developed two  specific objectives: 1) Determine the potential of gene flow and hybridization via pollen flow from B. napus to related Brassica vegetable crops; 2) Evaluate whether transgenes from B. napus will be detectable in viable and non-viable outcrossed Brassica vegetable seed. In-field crossing experiments were conducted in 2007 and 2008 using receptor plants placed within a conventional (non GMO) B. napus field. In each year, two independent crossing experiments, one using a self incompatible Brassica rapa var. chinensis, and a second using cytoplasmic male sterile (CMS) Brassica oleracea var. italica line were arranged in a 15 x15 m block within the field.  Once siliques had set on the receptor plants, each species was returned to the greenhouse and harvested individually. Results of the flow cytometry analysis conducted on the progeny indicate that hybridization does occur between B. rapa var. chinensis and B. napus, 23% in 2007 and 11% in 2008. However, all seed that were produced on the B. oleracea var. italica were shriveled and failed to germinate. Greenhouse crosses were conducted using transgenic (RoundUp Ready) B. napus and several cultivars of the previously mentioned vegetable species with blow flies (Diptera:Calliphoridae) as pollinators in enclosed cages. Results of these experiments indicate that outcrossing rates varied greatly (0.0026% to 15%) depending on B. rapa var. chinensis cultivar, and transgenes were detectable in both germinable and non-germinable seed produced on non-transgenic B. rapa female plants. Neither viable seed, nor transgenes were detected in any of B. oleracea greenhouse crosses.