The International Consortium on Agricultural Biotechnology Research (ICABR)


Pollen transport from genetically modified corn

J.M. Jemison, Jr., M. Vayda, University of Maine





Concern over the transport of genetically engineered (GE) corn pollen in the U.S. is growing. Organic producers fear the loss of their organic certification if GE proteins are found in their corn. Although corn pollen grains are among the heaviest of wind pollinated plants, transport is possible. Critics of GE frequently refer to the "gene cloud" of mutant corn pollen travelling distances of many miles to cross pollinate and contaminate non-GE corn. In 1999, we planted four research plots to corn between May 15 and May 17. An 83-day Roundup-Ready (RR) corn (DeKalb 335 RR) hybrid was used for two of these studies, and one of these studies was vandalized in August after the corn had shed pollen. These studies were located side by side. In the other two studies, (a phosphorus fertility trial and another weed control study), we planted another 83-day hybrid, Agway 144. Due to close planting dates and similar maturities, we were able to evaluate cross pollination of GE corn pollen with standard corn silage hybrids.

The two studies with RR corn located side by side were approximately 37,190 ft2 and were located between the two other corn trials. The phosphorus study was approximately 12,000 ft2 and was located 100 feet east of the RR study. The prevailing winds are southwestly, and this field should represent a worst-case scenario for cross pollination. The other weed control study was located 1150 feet southwest of the RR study. The size of that plot was 11,520 ft2. Due to the greater distance and direction, this represents a reduced chance for cross pollination. To evaluate the effect of position in the field, we divided each study into three areas: closest to the field, a middle section and a section farthest away from the GE pollen source. Four replicate samples were collected from each study. We collected corn from the RR study offspring as well. A figure showing the layout is presented below.

Corn was harvested from each study on September 17 to provide seed for germination in the greenhouse. We collected 100 ears from each location within each study area. Corn ears were dried in a greenhouse, and seeds were sown in 0.14 m2 greenhouse flats with potting soil at one cm spacing or approximately 170 seeds/flat. Plant emergence was over 90%. At the 2 leaf stage, plants were sprayed by hand with a 0.5% solution of glyphosate. Surviving plants were scored, harvested, dried, and above-ground biomass measured. This process was repeated four times. The highest cross-pollination was found 100 ft from the GM source at 1%. Cross pollination dropped to 0.1% in the center tier and 0.03% in the farthest tier. No cross-pollination was found in the weed control experiment. Offspring of the RR plants had 72% survival, 98% of the RR parents survived, and none of the Ag144 survived glyphosate application. Although cross-pollination does occur, it appears to drop off exponentially with distance from the source. We will repeat this study in 2000.



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