Abstract
The ladybird Propylea japonica, adults of the green lacewing Chrysoperla nipponensis and the honey bee Apis mellifera are common pollen feeders in many crop systems. They could therefore be directly exposed to Cry proteins in Bacillus thuringiensis (Bt)-transgenic crop fields by ingestion of pollen. They, or closely related species, are therefore often selected as surrogate test species in non-target risk assessment of Bt plants. In the current study, we evaluated the potential effects of the ingestion of Bt maize pollen containing the Cry1Ab/Cry1Ac fusion protein on various life-table parameters of the three pollen-feeding non-target species in laboratory feeding assays. The results showed that pupation rate and male adult fresh weight of P. japonica were significantly increased when fed pollen from Bt maize compared to control maize pollen, but other test life-table parameters were not affected. For the other two species, none of the tested life-table parameters (survival, pre-oviposition period, fecundity and adult fresh weight for C. nipponensis; survival and mean acinus diameter of hypopharyngeal glands for A. mellifera) differed between non-Bt and Bt maize pollen treatments. ELISA measurements confirmed the stability and uptake of the Cry protein by all three species during the feeding bioassays. In addition, a sensitive insect bioassay confirmed the bioactivity of the Cry1Ab/Cry1Ac protein in the Bt maize pollen used. Overall, the results suggested that the three pollen feeders are not sensitive to the Cry1Ab/Cry1Ac protein, and planting of the Bt maize variety will pose a negligible risk to P. japonica, adult C. nipponensis and adult A. mellifera.
Highlights
Since first commercialized in 1996, genetically engineered (GE) maize varieties that produced insecticidal proteins from Bacillus thuringiensis (Bt) to control Lepidoptera and/or Coleoptera pestsToxins 2019, 11, 8; doi:10.3390/toxins11010008 www.mdpi.com/journal/toxinsToxins 2019, 11, 8 are planted on increasing areas worldwide [1,2]
There is a great variety of arthropods present in agro-ecosystems, but only a small fraction of species can be tested to support the non-target risk assessment of Bt plants
Species are selected that contribute to important ecological functions, have economic or aesthetic value, are rare or endangered, are likely to be exposed to the insecticidal protein(s) expressed in the crops, and are available and amenable for testing under controlled laboratory conditions [20,25]
Summary
Since first commercialized in 1996, genetically engineered (GE) maize varieties that produced insecticidal proteins from Bacillus thuringiensis (Bt) to control Lepidoptera and/or Coleoptera pests. The assessment of non-target effects focuses on species that have economic or ecological value and that are likely to be exposed to the insecticidal compound produced by the plant [19,20,21] These include natural enemies such as predators and parasitoids that help control herbivores, pollinators, and species that support nutrient cycling, i.e. detritivores. The honey bee Apis mellifera adult (Hymenoptera: Apidae) is a pollinator of ecological and economic importance that consumes maize pollen For this reason, A. mellifera is commonly used to assess the non-target effects of Bt-transgenic crops [9,20,28,29,30,31]. Cry1Ab/Cry1Ac protein on pollen-consuming beneficial species including the predators P. japonica and C. nipponensis and adults of the honeybee A. mellifera in the laboratory
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