Risikobewertung von gentechnisch verändertem Mais im Hinblick auf ausgewählte Schmetterlinge der Agarlandschaft

  • Risk assessment of genetically engineered maize with regard to selected butterflies in the agricultural landscape

Schuppener, Mechthild; Slusarenko, Alan (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2011, 2012)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2011

Abstract

The cultivation of genetically engineered maize expressing lepidopteran-specific Bt proteins poses a potential risk for non-target butterflies. For a comprehensive environmental risk assessment (ERA) both hazard and exposure have to be considered. To assess hazard it is essential to determine the toxicity of the Bt proteins contained in maize pollen. To estimate exposure the dispersion of maize pollen by wind and its deposition on the host plants of non-target butterfly larvae have to be measured. Furthermore, data on the occurrence of larvae in the field during the time of maize anthesis are required. The aim of this work was to conduct an ERA for two selected European non-target butterfly species, Aglais urticae and Inachis io, and the stacked Bt maize DKc 5143-Bt (MON89034 x MON88017), expressing the lepidopteran-specific Cry proteins Cry1A.105 and Cry2Ab2, and the coleopteran-active Cry3Bb1. In addition, methods for a post-market environmental monitoring (PMEM) were developed and assessed. In laboratory feeding studies larvae were fed leaf discs of their host plant Urtica dioica treated with different amounts of pollen of the Bt maize. Pollen of the near-isogenic line DKc 5143 and the conventional line Benicia, and pure water served as controls. To quantify the exposure of larvae the pollen density on U. dioica leaves was assessed in different distances and all directions around a maize field. In addition, butterfly nests were mapped in two different agrarian regions during maize anthesis with emphasis on the distances of nests to maize fields. The feeding studies with A. urticae showed first significant differences between the Bt treated group and the control groups at pollen doses between 200 and 400 grains/cm2 for feeding activity, developmental time and mortality. No effects on I. io were observed at the tested pollen densities. The pollen density found on U. dioica leaves was 34 grains/cm2 on average (max.=212 grains/cm2) directly at the maize field margin. In a distance of 5 m the mean pollen density was only 3 grains/cm2 (max.=22 grains/cm2). In one region more than 60% of the butterfly nests were located in distances of between 0 and 5 m to the next maize field, while in the other region more than 50% of nests were located in more than 100 m to the nearest maize field. While the laboratory feeding studies showed sublethal and lethal effects on larvae after feeding on Bt maize pollen, exposure in the field was very low. In conclusion, the environmental risk for A. urticae and I. io posed by event MON89034 x MON88017 can be regarded as negligible. The mapping of the easily recognisable nests of A. urticae and I. io in combination with analyses of data using a geographical information system can be used for PMEM. Monitoring needs to consider the different characteristics of the agricultural regions, since they may play a big role in shaping the exposure of non-target species.

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