Updated: Sep 16, 2020
On April 11, 2016 / Bees, Brassica, Canola, GE Avoidance, GE
Canola (Brassica napus; B. rapa)
Canola is a high-risk crop in terms of contamination from GMOs. Its basic biology along with its ability to persist outside of cultivation in disturbed habitats (like field edges and roadsides) presents multiple avenues of potential contamination.
And contamination poses threat beyond canola seed growers due to its sexual compatibility with other members of the Brassica family.
There is potential for trangenes from B. napa canola to move to B. napa vegetables (rutabaga and Siberian kale) and to B. rapa vegetables−including turnip, broccoli rabe, Chinese cabbage, Chinese mustard, and other Asian Brassica vegetables−because they share a common set of chromosomes. International seed growing standards dictate a buffer of approximately 2 miles surrounding compatible Brassica vegetable seed fields.
Canola’s potential for wide pollen dispersal is aided by its long flowering window, up to 40 days, as well as the durability of the pollen itself. Canola pollen can remain viable a full week in ideal conditions.
Canola is also a candidate for contamination via inadvertent mixing. Small seed size makes it likely to remain in transportation or storage vessels, as well as harvesting and cultivating equipment. One University of California Cooperative Extension agent likens trying to encase canola seed for transport to containing water. Canola is so tiny that it flows through the cracks . Roughly 4 lbs. of seed, 500,000 seeds, can easily be left inside a combine. Additionally, plows carrying residual soil may also transport residual seed.
Studies in Manitoba, Canada, determined that harvested canola seed is left in the field at rates of 3 to 10%. However, up to 50% is not unheard of.
Residual seed can and does result in volunteer and feral populations of canola. A study from University of California Cooperative Extension found that shatter at harvest can produce up to 10 times the initial first-generation seeding rate over the course of subsequent years.
Volunteer populations, in turn, can act as additional pollen sources outside of cultivated crops.
In the U.S., wild populations of canola were first identified in 2010 in North Dakota. Feral populations exhibited two different types of transgenes: one resistant to glyphosate, the other modified to resist gluphosinate. Canola’s compatible weedy relatives, including B. rapa and R. raphanistrum (wild radish), are considered “bridge species” as the resulting canola-weed hybrids may be sexually compatible with yet another species of Brassica.
Planting canola or sexually compatible Brassica this season? Decrease your crop’s risk of GE contamination, and read the full canola chapter in Protecting Organic Seed Integrity: The Organic Farmer’s Handbook to GE Avoidance and Testing. The handbook is available as a free download.
Best Management Strategies for Canola & Compatible Brassicas…
• Identify potential points of contamination.
• Plant clean seed in fields a minimum of 1 mile from GE canola stands. 5 miles is better if possible. 10 miles is encouraged in the presence of honeybees.
• Avoid renting pollinators previously used in/near GE canola.
• Control volunteer/feral populations of canola near seed fields.
• Manage volunteer seed bank by minimizing seed shatter in the field. This can be done by harvesting at the right time with properly calibrated equipment.
• Plan cultivation practices to deplete a potential seed reservoir; this includes stale seed bed techniques and avoiding deep cultivation. Also use crop rotation.
• Avoid mixing seed during harvest, cleaning, storage, transport, sales. Use dedicated equipment and facilities if possible. Otherwise, clean thoroughly between use.