A Transgenic World: GMOs: Bt crops explained

We have talked about putting a gene of interest into a plant. But we haven't talked about what those genes may be. One common gene in crops and on the market are the "Bt" crops. There is Bt-corn, Bt-cotton and Bt-potatoes among others.

Bt stands for Bacillus thuringiensis. In nature one of the greatest reservoirs for bacteria is the soil. Thousands and thousands of different types of bacteria live in our soil. Bacteria from soil samples can be cultured and studied as was the case with B. thuringiensis. This bacteria has a gene that produces a protein that is toxic to Lepidoptera, a fancy word for caterpillars. One Lepidoptera that is a significant pest is the European Corn borer and its impact is significant.

The University of Minnesota reports: "European corn borer, Ostrinia nubilalis, is the most damaging insect pest of corn throughout the United States and Canada (Figs. 1 and 2). Losses resulting from European corn borer damage and control costs exceed $1 billion each year. For example, losses during a 1995 outbreak in Minnesota alone exceeded $285 million. A recent four-year study in Iowa indicated average losses near 13 bushels per acre in both first and second generations of European corn borer, for total losses of about 25 bushels per acre."

Controlling insects like the European corn borer and other pests is very important and the use of Bt GMO can control these insects. An insect that ingests plant material that is expressing the Bt protein will quickly stop feeding as quick as 2 hours after the first bite and if they eat enough they will usually die in a couple days. The protein binds to the insect's gut and breaks the gut down and forms pores. When the gut breaks down all types of bacteria are introduced to the insect's bloodstream it will most likely die of septicemia.

Bt crops allow farmers to reduce the need to spray insecticides for many Lepidoptera pests, a boon to the environment and saved labor and chemical costs for the farmer. Even when you do spray chemicals they are only about 80% effective compared to about 96% effectiveness from Bt. (University of Minnesota)

And most importantly Bt is safe.

"Humans exposed orally to 1000 mg/day for 3-5 days of Bt have showed no ill effects. Many tests have been conducted on test animals using different types of exposures. The results of the tests showed that the use of Bt causes few if any negative effects. Bt does not persist in the digestive systems of mammals." Reference: Bacillus thuringiensis: Biology, Ecology and Safety, Glare, T.R., O'Callaghan, M. (2000) ISBN 0-471-49630-8

Another summary of safety info taken from the University of Minnesota reports, "The EPA considered 20 years of human and animal safety data before registering Bt corn. Bt proteins are not toxic to people, domestic animals, fish, or wildlife; and they have no negative impacts on the environment. The Food and Drug Administration (FDA) exempts Bt Cry proteins from residue analyses because of Bt's history of safety and because these proteins degrade rapidly."

Bt crops show just how effective and safe GMO crops can be by controlling insects and reducing chemical use.