A critical assessment of the effects of Bt transgenic plants on parasitoids.
The ecological safety of transgenic insecticidal plants expressing crystal proteins (Cry toxins) from the bacterium Bacillus thuringiensis (Bt) continues to be debated. Much of the debate has focused on nontarget organisms, especially predators and parasitoids that help control populations of pest insects in many crops. Although many studies have been conducted on predators, few reports have examined parasitoids but some of them have reported negative impacts. None of the previous reports were able to clearly characterize the cause of the negative impact. In order to provide a critical assessment, we used a novel paradigm consisting of a strain of the insect pest, Plutella xylostella (herbivore), resistant to Cry1C and allowed it to feed on Bt plants and then become parasitized by Diadegma insulare, an important endoparasitoid of P. xylostella. Our results indicated that the parasitoid was exposed to a biologically active form of the Cy1C protein while in the host but was not harmed by such exposure. Parallel studies conducted with several commonly used insecticides indicated they significantly reduced parasitism rates on strains of P. xylostella resistant to these insecticides. These results provide the first clear evidence of the lack of hazard to a parasitoid by a Bt plant, compared to traditional insecticides, and describe a test to rigorously evaluate the risks Bt plants pose to predators and parasitoids.
Department of Entomology, Cornell University/New York State Agricultural Experiment Station (NYSAES), Geneva, New York, United States of America.
Mao
M
Chen
Jian-Zhou
JZ
Zhao
Hilda L
HL
Collins
Elizabeth D
ED
Earle
Jun
J
Cao
Anthony M
AM
Shelton
D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics* / Q000472:pathogenicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D003368:Gossypium / Q000235:genetics / Q000382:microbiology / Q000469:parasitology; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D007305:Insecticide Resistance / Q000502:physiology; D007814:Larva / Q000382:microbiology / Q000469:parasitology; D009036:Moths / Q000382:microbiology / Q000469:parasitology; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000382:microbiology / Q000469:parasitology*; D014863:Wasps / Q000378:metabolism* / Q000382:microbiology; D003313:Zea mays / Q000235:genetics / Q000382:microbiology / Q000469:parasitology
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis