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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #305693
Title: Bacillus thuringiensis plants expressing Cry1Ac, Cry2Ab and Cry1F are not toxic to the assassin bug, Zelus renardii

Author
item SU, HONG-HUA - Cornell University
item TIAN, JUN-CE - Cornell University
item Naranjo, Steven
item ROMEIS, JORG - Agroscope
item Hellmich Ii, Richard
item SHELTON, ANTHONY - Cornell University

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2014
Publication Date: 11/26/2014
Citation: Su, H., Tian, J., Naranjo, S.E., Romeis, J., Hellmich II, R.L., Shelton, A.M. 2014. Bacillus thuringiensis plants expressing Cry1Ac, Cry2Ab and Cry1F are not toxic to the assassin bug, Zelus renardii. Journal of Applied Entomology. 139:23-30.

Interpretive Summary: Genetically engineered insect-resistant crops, producing insecticidal crystal (Cry) proteins from the bacterium Bacillus thuringiensis (Bt), have revolutionized insect control and become a major tool for integrated pest management (IPM) programs. There are concerns, however, about the ecological risk of GE crops, especially potential risk to insects that provide biological control services. Such non-target insects like the assassin bug, Zelus renardii, from this study are exposed to Bt proteins when they consume prey that have fed on a Bt crop. The challenge in studying these tri-trophic interactions is that the prey itself is often harmed by the Bt protein, which makes it difficult to separate the effects of prey quality from Bt effects on the natural enemy. The prey-quality problem is addressed by using fall armyworms, Spodoptera frugiperda, that are resistant to Bt corn (Cry1F protein) and cabbage loopers, Trichoplusia ni, that are resistant to Bt cotton (Cry1Ac and Cry2Ab proteins) as prey for the assassin bug. Tests demonstrated that these proteins were present in the plant at the highest levels, at lower levels in the prey and at the lowest levels in the predator. Furthermore, survival, larval duration, adult weight, adult longevity and female fecundity of the assassin bug were not different when they were fed resistant prey larvae of fall armyworm or cabbage looper reared on either a Bt crop or the respective non-Bt crop. Our results indicate that the assassin bug was exposed to Cry1F and Cry1Ac and Cry2Ab when it fed on hosts that consumed Bt-transgenic plants, but the proteins did not affect important fitness parameters in this common and important predator. 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: Cotton and maize delivering insecticidal crystal (Cry) proteins from the bacterium, Bacillus thuringiensis (Bt), have been commercialized since 1996. Bt plants are subjected to environmental risk assessments for non-target organisms, especially natural enemies that suppress pest populations. In this study, we used Cry1F-resistant Spodoptera frugiperda (J.E. Smith) and Cry1Ac and Cry2Ab-resistant Trichoplusia ni (Hübner) as prey for the assassin bug, Zelus renardii (Kolenati), a common predator in maize and cotton fields. In tri-trophic studies we assessed several fitness parameters of Z. renardii when it fed on resistant S. frugiperda that had fed on Bt maize expressing Cry1F or on resistant T. ni that had fed on Bt cotton expressing Cry1Ac and Cry2Ab. ELISA tests demonstrated that these proteins were present in the plant at the highest levels, at lower levels in the prey and at the lowest levels in the predator. Furthermore, survival, larval duration, adult weight, adult longevity and female fecundity of Z. renardii were not different when they were fed resistant prey larvae (S. frugiperda or T.ni) reared on either a Bt crop or the respective non-Bt crop. Our results indicate that Z. renardii was exposed to Cry1F and Cry1Ac and Cry2Ab when it fed on hosts that consumed Bt-transgenic plants, but the proteins did not affect important fitness parameters in this common and important predator.