May 2010
URL: http://www.kingcorn.org/news/timeless/BiotechTraits.html

A Compendium of Biotech Corn Traits

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen at purdue.edu
 

Click image to view larger version.
Percent of U.S. corn acres planted to
biotech corn hybrids since 2000.

orn hybrids containing transgenic traits (aka GMO, biotech) were once a novelty, but now occupy the overwhelming majority of the acres of commercial dent corn grown in the U.S. In 2009, the United States Dept. of Agriculture estimated that approximately 85% of the U.S. corn acres were planted to biotech hybrids (USDA-NASS, 2009).

The two broad categories of transgenic traits available to U.S. corn growers today include resistance to certain insect pests and tolerance to certain herbicides. No more. No less. Sounds simple, doesn't it?

Well, it is a little more complex than that.

There are two general categories of transgenic insect resistance available in corn. Both are governed by genes obtained from soil bacteria known as Bacillus thuringiensis and are referred to as "Bt" genes. The first category of Bt genes confer resistance to rootworm species (Coleoptera, Diabrotica sp.). The other category of Bt genes confer resistance to "moth" type insects such as European corn borer, Southwestern corn borer, western bean cutworm, fall armyworm, corn earworm, and black cutworm. Within each category of insect resistance, plant breeders have available two or more "flavors" of the Bt gene that they can work with.

There are also two broad categories of herbicide tolerance biotech traits in corn. One confers tolerance to glyphosate (Roundup® and assorted generics) and the other offers tolerance to glufosinate (the so-called "Liberty Link" trait).

Click image to view larger version.

European corn borer larva.

To complicate things further, biotech traits are not defined simply by the particular "flavor" of the responsible transgene. The chromosomal location of the transgene also defines the genetic event. Two different genetic events may contain the same "flavor" of a transgene, but are marketed under different trade names because the transgenes occupy different positions within the chromosomal makeup of the hybrid. One example is Syngenta's Agrisure® CB/LL trait and Monsanto's YieldGard® Corn Borer trait. Both traits contain the same Bt transgene (Cry1Ab), but because the transgenes occupy different chromosomal locations they are named as different genetic events (Bt11 vs. Mon810) and marketed under different trade names.

Additionally, this Syngenta event also contains the "pat" transgene that confers tolerance to the herbicide glufosinate. The "pat" transgene was included in the event as a selectable marker that enabled the researchers to more easily identify "successful" genetic transformations during the development of the Bt event. This dual-purpose use of the "pat" transgene for glufosinate tolerance is also evident in the TC 1507 and DAS-59122-7 Bt events from Dow Agrosciences / Pioneer Hi-Bred, but not in the Monsanto Bt events.

Finally, so-called "stacked" hybrids contain two or more biotech traits packaged together in a single hybrid. For example, Monsanto's YieldGard® Plus contains two Bt transgene events; one for the control of rootworms and one for control of several of the corn borer species.

So, even though there are only two broad categories of biotech traits available in corn today, there are many different "flavors" to choose from, packaged in many different combinations and it is easy for growers and consultants alike to become confused. The following table lists and describes the biotech traits available in 2010 for U.S. corn growers according to the trade name of the transgene event.

The information was copied directly from a database maintained and published by the National Corn Growers Association (NCGA). The information is based on annual surveys of the seed industry by the NCGA and, consequently, the accuracy the information is dependent on the accuracy of the completed surveys.

For the latest up-to-date listing of biotech traits, visit the NCGA database online at http://www.ncga.com/know-you-grow. That Web site offers the additional advantage in that you can click on each event name to view a list of commercial hybrid names and brands that contain each specific event.

A complementary source of background information on transgenic crops of all sorts is the GM Crop Database maintained by the Center for Environmental Risk Assessment. This resource offers more technical information about the myriad of transgenic events that exist today.

Related References

Acreage. 30 June 2009. USDA Nat'l Ag. Statistics Service. [online] http://usda.mannlib.cornell.edu/usda/nass/Acre//2000s/2009/Acre-06-30-2009.pdf [URL accessed May 2010].

CERA. (2010). GM Crop Database. Center for Environmental Risk Assessment (CERA), ILSI Research Foundation, Washington D.C. [online] http://cera-gmc.org/index.php?action=gm_crop_database [URL accessed May 2010].

Know Before You Grow. 2010. National Corn Growers Association. [online] http://www.ncga.com/know-you-grow [URL accessed May 2010].

For other timely crop management info...
Chat 'n Chew Cafe: http://www.kingcorn.org/cafe
CNN Archives: http://www.kingcorn.org/news/archive.html

© 2010 , Purdue University, an equal access, equal opportunity university. This material may be available in alternative formats. If you have trouble accessing this page because of a disability, please contact RLNielsen at rnielsen@purdue.edu.