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Unintended Effects of Genetic Manipulation


Alpha-Amylase Inhibitor


Peas engineered to be weevil-resistant elicited immune reactions in mice.

Peas engineered to be weevil-resistant had lowered starch digestibility when fed to chickens and pigs.

Bacillus thuringiensis (Bt)


Innate Immunity is Affected in Insect-Resistant GM Aspens.

“Leaf Litter from Insect-Resistant Transgenic Trees Causes Changes in Aquatic Insect Community Composition”.

Insects feed less on insect-resistant aspen leaves, but the trees don’t grow larger than unmodified aspens.


Bt cotton showed decreased ability to kill cotton bollworm larvae during flower development and flowering.

Bt cotton had altered protein metabolism and produced less insecticidal toxin in leaves when subjected to high temperatures during boll formation.

Cotton plants and seeds expressing Bt toxin were found in non-Bt refuges.

Insect-resistant, transgenic cotton was more susceptible to fungal disease than its parent line.

GM cotton and suicide rates

Traditional Non-GMO Cotton Can Yield Economic Benefits Similar to GMO Cotton on Non-Irrigated Small Farms in India

Adoption of GM Cotton Slowing in West Africa Due to Concerns About Inferior Qualities of Crop


Bt maize has higher lignin content.

Atlantic salmon fed Bt corn had altered enzyme activity in liver and intestine as well as altered proportions and numbers of different white blood cells.

Monarch butterfly larvae exposed to anthers from Bt maize ate less and gained less weight.

Byproducts from Bt maize enter streams, and in feeding experiments affected stream insects.

Bt maize varieties matured more slowly and had on average lower grain yield and higher grain moisture content than conventional varieties.

Bt maize had changed lipid composition in stems; also, lipid composition in soil was altered, and soil respiration was reduced.

Western corn rootworms were found feeding on volunteer corn plants expressing a Bt toxin specific to that pest.

The transgenic sequences of some Bt maize plants have changed since they were approved.

Western Corn Rootworm Not Killed by Bt Corn in Iowa.


Insect-resistant transgenic potatoes had less foliage and altered levels of leaf-glycoalkaloids.


Bt rice showed signs of dwarfism and other abnormalities.

Genetically modified (GM) insect-resistant rice and weedy rice hybrids have increased seed production.

Yield differences between insect-resistant Bt rice and non-GM rice.

root nodule bacteria

Root nodule bacteria with Bt transgene tended to displace non-manipulated bacteria in legume root nodules.


Wild sunflowers with transgene for Bt toxin produced more seeds than normal wild sunflowers.

Bt resistance in general

Increasing resistance of pests to genetically modified, insect-resistant Bt crops.

Field performance of Bt Transgenic crops: A review.



Lectin transgene for stemborer resistance alters growth of sugarcane.



Pheromone-producing GM wheat does not repel pests in field trials.

RNAi interference

Potential unintended effects of RNAi-based insecticidal crops.

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