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Title: Bt crops producing Cry1Ac, Cry2Ab and Cry1F do not harm the green lacewing, chrysoperla rufilabris

Author
item TIAN, J - Cornell University
item WANG, X - Yangtze University
item LONG, L - Guangxi Academy Of Agricultural Sciences
item ROMEIS, J - Agroscope
item Naranjo, Steven
item Hellmich Ii, Richard
item WANG, P - Cornell University
item EARLE, E - Cornell University
item SHELTON, A - Cornell University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2013
Publication Date: 3/27/2013
Publication URL: http://handle.nal.usda.gov/10113/56012
Citation: Tian, J.C., Wang, X.P., Long, L.P., Romeis, J., Naranjo, S.E., Hellmich II, R.L., Wang, P., Earle, E.D., Shelton, A.M. 2013. Bt crops producing Cry1Ac, Cry2Ab and Cry1F do not harm the green lacewing, chrysoperla rufilabris. PLoS One. 8(3):e60125.

Interpretive Summary: Transgenic crops producing the target-specific insecticidal proteins of Bacillus thuringiensis (Bt) have been widely adopted and cultivated on millions of hectares globally. However, there remain concerns about the ecological risk associated with these crops, specifically the risk to non-target organisms. Of particular interest are non-target organisms that supply valuable ecosystem services such as natural enemies of pest insects. Insects that provide biological control services are typically exposed to the Bt proteins through the prey they consume that have fed on the Bt crop (tri-trophic interaction). A common problem in evaluating tri-trophic exposure is that the prey itself is often harmed by the Bt protein and thus it is impossible to separate the effects of prey quality from Bt toxicity on the natural enemy. Here we take advantage of cultures of two prey insects (cabbage looper and fall armyworm) that have been selected to be resistant to multiple Bt Cry proteins in three crop plants. Larvae of these species were fed Bt plants or non-Bt plants and then exposed to predaceous green lacewings, Chrysoperla rufilabris, an important natural enemy found in many crops and a common predator sold for augmentative biological control. Fitness parameters (larval survival, development time, fecundity and egg hatch) of green lacewing were assessed over two generations. There were no differences in any of the fitness parameters regardless if the predator consumed prey that had in turn consumed Bt or non-Bt plants. Additional studies confirmed that the prey consumed by the predator contained bioactive Cry proteins. These studies confirm that Cry1Ac, Cry2Ab and Cry1F do not pose a hazard to the important predator C. rufilabris. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non-target organisms. These results should be useful to governmental regulators, scientists interested in ecological risk assessment and others concerned about the risks of Bt transgenic crops.

Technical Abstract: The biological control function provided by natural enemies is regarded as a protection goal that should not be harmed by the application of any new pest management tool. Plants producing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling pest Lepidoptera on cotton and maize and risk assessment studies are needed to ensure they do not harm important natural enemies. However, using Cry protein susceptible hosts as the prey often compromises such studies. To avoid this problem we utilized pest Lepidoptera that were resistant to Cry1Ac produced in Bt broccoli (Trichoplusia ni), Cry1Ac/Cry2Ab produced in Bt cotton (T. ni), and Cry1F produced in Bt maize (Spodoptera frugiperda). Larvae of these species were fed Bt plants or non-Bt plants and then exposed to predaceous green lacewings, Chrysoperla rufilabris. Fitness parameters (larval survival, development time, fecundity and egg hatch) of C. rufilabris were assessed over two generations. There were no differences in any of the fitness parameters regardless if C. rufilabris consumed prey (T. ni or S. frugiperda) that had consumed Bt or non-Bt plants. Additional studies confirmed that the prey consumed by the predator contained bioactive Cry proteins. These studies confirm that Cry1Ac, Cry2Ab and Cry1F do not pose a hazard to the important predator C. rufilabris. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non-target organisms.