Food and Drug Administration regulates genetically modified foods, it considers Bt-corn to be nutritionally equivalent to traditional corn. To transform a plant into a GMO plant, the gene that produces a genetic trait of interest is identified and separated from the rest of the genetic material from a donor organism. Most organisms have thousands of genes, a single gene represents only a tiny fraction of the total genetic makeup of an organism.
A donor organism may be a bacterium, fungus or even another plant. In the case of Bt corn, the donor organism is a naturally occurring soil bacterium, Bacillus thuringiensis, and the gene of interest produces a protein that kills Lepidoptera larvae, in particular, European corn borer.
This protein is called the Bt delta endotoxin. Growers use Bt corn as an alternative to spraying insecticides for control of European and southwestern corn borer. The Bt delta endotoxin was selected because it is highly effective at controlling Lepidoptera larvae, caterpillars.
It is during the larval stage when most of the damage by European corn borer occurs. The protein is very selective, generally not harming insects in other orders such as beetles, flies, bees and wasps. For this reason, GMOs that have the Bt gene are compatible with biological control programs because they harm insect predators and parasitoids much less than broad-spectrum insecticides.
The Bt endotoxin is considered safe for humans, other mammals, fish, birds, and the environment because of its selectivity. Bt has been available as a commercial microbial insecticide since the s and is sold under many trade names.
These products have an excellent safety record and can be used on many crops until the day of harvest. To kill a susceptible insect, a part of the plant that contains the Bt protein not all parts of the plant necessarily contain the protein in equal concentrations must be ingested. A: Bt corn pollen counts within Ontario fields averaged grains per in 2 of milkweed leaf.
The highest counts in this study were just below grains per in 2 of milkweed leaf. Q: Do lethal doses of Bt corn pollen occur on milkweed plants near Bt cornfields? A: Corn pollen is relatively heavy and does not travel far. Milkweed plants three feet from Ontario cornfields averaged pollen grains per in 2 of milkweed leaf and milkweed plants 15 feet from the field averaged nine pollen grains per in 2 of milkweed leaf. Rainfall greatly reduces pollen densities on milkweed plants in cornfields.
Q: Are there sublethal effects for Monarch caterpillars that feed on Bt corn pollen? A: Little is known about sublethal effects such as reduced growth or delayed development. However, it has been noted that Monarch caterpillars consume less when fed milkweed leaves containing Bt corn pollen than when fed clean leaves. A: The more synchrony there is between pollen shed and the presence of small Monarch caterpillars on milkweed, the greater the risk from Bt corn.
Currently, researchers believe that there is little overlap between the two, but both are variable events influenced by weather and location so there may be situations where they are well synchronized.
Q: Is there anything that can be done to protect the Monarch butterfly from Bt corn pollen in Colorado? A: The threat to Monarchs in Colorado is quite low since the Monarch butterfly is rare in our state. Where Monarchs are more common, the EPA suggests planting non-Bt corn as a pollen trap around the field or consider prevailing wind direction and likely Monarch habitat locations when deciding where Bt corn and non-Bt corn should be planted.
These suggestions would also serve to minimize the risk to other nontarget caterpillars that might be of concern. A: Many species of caterpillars occur in and around cornfields during the growing season, and might be affected by Bt corn. This will be a continuous concern as new events are introduced in corn and as other modified crops are developed. One Midwest study showed that black swallowtail larvae were unaffected by Bt corn pollen, but another indicated that event pollen could have sublethal effects on this species.
However, the detailed set of studies currently underway on the Monarch butterfly have not been undertaken for this insect. Q: Is it true that the roots of Bt corn plants leak delta endotoxins into the soil? A: Yes, this has been demonstrated in several laboratory studies.
However, the implications for various soil organisms are unclear. Since Bt is a very common soil bacterium, it is likely that exposure of these organisms to Bt toxins is common. The levels of Bt toxins measured in the lab studies were at least 10 times below those that cause observable effects in important soil organisms such as earthworms and springtails.
Q: The alternative to Bt corn seems to be the use of conventional insecticides. Which is more harmful to nontarget insects, such as the Monarch butterfly?
A: Results from studies of non-target effects indicate that the risks are relatively small. Also, millions of acres of forests have been treated for gypsy moth and other pests with Bt insecticides over the past 30 years with little documented effect on nontarget species. On the other hand, the hazards of conventional insecticides to many different nontarget insect species are very well documented.
Q: Will Bt corn affect other insects, such as natural enemies predators and parasitic insects? A: This is a complicated question because of the many species involved. There are at least three important effects. Insecticide use is lowered by the use of Bt corn if the main pests are susceptible to Bt toxins, so natural enemies will be less affected by exposure to these chemicals.
This likely is the most significant effect. Secondly, since the target pest is essentially eliminated from the crop by the Bt toxin, any natural enemy that relies on the pest for food will be negatively affected. While this is possible, the crop protection benefits of eliminating the pest likely outweigh the loss of control provided by the natural enemy. Also, biological control often is the result of the actions of a complex of natural enemy species so the overall natural enemy benefit may not be greatly affected.
Finally, natural enemies that feed on pests that have ingested the Bt toxin may be negatively affected by the toxin. This interaction has been demonstrated, however, the negative effects on the natural enemies are thought to be relatively minor.
Is this true? A: Some experimental transgenic plants have caused allergic responses. The EPA requires several food allergen tests as part of the registration process for transgenic crops containing pesticidal substances. The first test measures the length of time that the potential allergen survives in an acid environment.
Longer survival times indicate more likelihood of surviving the digestion process and being absorbed into the blood stream, which is the first step in food allergenicity. Delta endotoxins and VIPs produced by the currently available events all are rapidly broken down in the stomach and thus are not potential food allergens.
If you would like to attend a seminar, online course or an on-campus course to learn more about biotechnology in plants or work on a college degree, contact Kathy Schindler in the Department of Agronomy and Horticulture at Click links here below to watch animations in a new window which depict more details involved with each of these steps:.
Skip to main content. All of the DNA from Bacillius thiurengensis , is isolated in a laboratory. In the laboratory the specific DNA sequence which makes up the cry 1Ab gene is found and copied.
The cry 1Ab soil bacterium version of the gene is modified slightly so that it will work better once in a corn plant. In a laboratory a corn plant is transformed with this new modified cry 1Ab gene which will provide the corn plant with insecticidal protection. The corn plant which is able to be transformed does not contain all of the optimal genes which a producer needs in the field.
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