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Agronomic Crops Network

Ohio State University Extension


Isolation Requirements for Identity Preserved (IP) Non-GMO Corn Production

Managing pollen drift is an important consideration in the production of specialty corns and non-GMO (non-transgenic) corn as IP grain crops. Corn is a cross-pollinating crop in which most pollination results from pollen dispersed by wind and gravity. Although most of a corn field’s pollen is deposited within a short distance of the field, with a 15-mph wind pollen may travel as far as 1/2 mile in a couple of minutes. Pollen from corn containing transgenes—genetically modified organism (GMOs), such as Bt corn―may contaminate (by cross-pollination) nearby non-GMO corn. 

The European Union guidelines require that foods, including grains, containing more than 0.9 percent biotech material (GMOs) are labeled as genetically engineered. Ohio producers of IP non-GMO corn, such as organic farmers, need to minimize pollen contamination by GMO corn if they are to obtain premiums. This can be challenging since most of the corn planted in Ohio is GMO corn. Growers can follow several planting practices to minimize GMO pollen contamination, including use of isolation and border rows, planting dates and/or hybrid maturity. 

Several state seed certification agencies that offer IP grain programs for corn require that non-GMO IP corn be planted at a distance of at least 660 feet from any GMO corn. This isolation distance requirement may be reduced by removing varying numbers of non-GMO border rows, the number of which is to be determined by the acreage of the non-GMO IP corn field. These isolation and border-row requirements are designed to produce corn grain that is not more than 0.5 percent contaminated with GMOs. 

In recent years the demand for organic corn has increased sharply. Although organically produced corn hybrid seed is available for planting, some organic corn growers prefer to grow open-pollinated varieties. Open-pollinated varieties are perceived as more nutritional and less likely to have been contaminated by transgenic traits. Because of their superior agronomic performance, hybrids account for nearly all the corn produced in the U.S. In comparisons of open-pollinated varieties with hybrids in the Ohio Corn Performance Test, hybrid yields averaged 60 percent greater than those of the open-pollinated varieties. Stalk lodging was higher in the open pollinated varieties (29 percent versus 8 percent). 

Several seed companies producing non-GMO corn seed for organic growers have been marketing hybrids that contain the PuraMaizeTM gene system, also known as the Ga1-s isolating mechanism. This is a naturally occurring gene in corn that impedes pollen originating from a plant that does not have the Ga1-s gene from being able to pollinate a plant that does have the Ga1-s gene. As a pollen recognition system, corn plants that contain the PuraMaize gene system will quickly accept pollen from other PuraMaize plants and essentially block pollen from foreign plants, such as GMO corn, allowing the pollen from PuraMaize plants to fertilize the developing kernels.