Potential impact of Diabrotica resistant Bt-maize expressing Cry3Bb1 on ground beetles (Coleoptera: Carabidae)

  • Potentieller Einfluss von Diabrotica resistentem, Cry3Bb1 exprimierendem Bt-Mais auf Laufkäfer (Coleoptera: Carabidae)

Priesnitz, Kai Uwe; Slusarenko, Alan (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2011)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2010

Abstract

The cultivation of genetically modified (GM) plants provides the possibility to address many needs of modern agriculture. The most important trait of GM crops besides herbicide tolerance is insect resistance provided by the expression of Bt proteins. Diabrotica virgifera virgifera will most probably become the new major pest in maize throughout Europe. For the control of this pest the GM maize DKC 5143-Bt (Event MON88017)was developed. This hybrid expresses the coleopteran specific Bt protein Cry3Bb1. The potential of these Bt crops to adversely affect nontarget organisms requires an environmental risk assessment (ERA) to be conducted before the release of the modified plants on the market. The potential impact of MON88017 on nontarget organisms was assessed in a field release experiment. The study examined the abundance of activity, a relative density, of ground beetles (Carabidae) in four maize varieties including the genetically modified MON 88017, the near-isogenic line DKC 5143 and the two conventional varieties DK 315 and Benicia. Carabidae are important predators of the biocenosis in maize fields and could get into indirect or direct contact with the Bt protein. During the growing period of maize pitfall traps were used to collect the ground dwelling arthropods, which were determined to species level. Statistical comparisons showed no significant differences of ground beetle activities between the four maize varieties. The internal content of the Bt protein Cry3Bb1 in ground beetles collected from the field was measured with DAS-ELISA. The Bt protein was found within 47% of the ground beetles sampled in Bt-plots before the anthesis and in 66% of the beetles collected after the beginning of maize anthesis. The absolute values of Cry3Bb1 in these samples ranged from 0.10 ng/g to a maximum of 5.16 µg/g protein/individual. The Bt content after the maize anthesis was significantly higher. Bio-assays in the laboratory showed the degradation of the Bt protein along the food chain. From the maize plant to the third trophic level, the carabid predators the Bt content was reduced to 5.5%. Additional toxicity tests revealed no effect of the Bt protein Cry3Bb1 on adult carabid beetles, even when consumed in artificially high concentrations. The environmental risk can be defined as a function of exposure and hazard. This study demonstrated the exposure of the carabids to the Cry3Bb1, but no impact (haz-ard) on the beetles was observed in the field and in additional bio-assays. Therefore a potential risk of the Bt maize hybrid MON 88017 on ground beetles can be regarded negligible. A future monitoring plan using carabid beetles as NTA test species would need consider the heterogeneity of the beetle community. Baseline data of every surveyed location will be necessary to gain sufficient results of a general surveillance.

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