Subproject: Exposure and effects of Bt-maize with multiple resistance-genes for nematodes Project aims

The stacked maize MON89034xMON88017 belongs to a new generation of Bt-maize with multiple, synthetic Bt-genes, that simultaneously produce three different Cry-proteins (Bt-toxins) (Cry1A.105; Cry2Ab2; Cry3Bb1). Therefore, the GM-plant is resistant against two maize pests, the European corn borer (Ostrinia nubilalis) and the Western corn rootworm (Diabrotica virgifera). The produced Bt-toxins, however, might also pose a risk to non-target soil fauna, which can be harmed by direct toxicity of Bt-toxins of indirect effects via the food-web. Nevertheless, it is assumed that due to the pest-specific resistance to the Bt-maize, non-target organisms are less harmed by the Bt-toxins compared to less specific pesticides.

If a soil organims can be affected by Bt-toxins depends on (1) the susceptability of a certain organism towards the toxins and (2) the exposure of the organism and (3) the bioavailability of the toxin for the organism. The feeding behavior of the organism is an important factor deciding if the toxins can be taken up. Within the joint research project „Freisetzungsbebleitende Sicherheitsforschung an Mais mit multiplen Bt-Genen zur Maiszünsler- und Maiswurzelbohrerresistenz“, this subproject primarily investigated the direct effects of the stacked Bt-maize on nema-todes in field trials, microcosm experiments and laboratory toxicity tests, by compar-ing the nematode's response to the treatment with non-Bt-maize or insectices. With the experimental set-ups, additional aspects, such as mode of action, bioavailability and exposure of the cry proteins for the nematodes could be considered.

Following hyposthes were tested:

• The cry proteins produced by the Bt-maize (Cry1A.105; Cry2Ab2; Cry3Bb1) cause structural changes of the nematode communities, that qualitatively differ from effects of pesticide treatment
• Bt- and insecticid effects differ from "cultivar effects".
• The feeding behavior of the nematodes is crucial for the uptake of cry proteins in nematodes, and thus for the toxic effect
• Cry-proteins that were taken up with the food (Cry1A.105; Cry2Ab2; Cry3Bb1) are able to bind to specific intestinal receptors in the nematodes to induce ef-fects at the molecular and organismic level.

Publicatios orgininating from this project:

Höss S, Reiff N, Ottermanns R, Pagel-Wieder S, Dohrmann AB, Tebbe CC, Traunspurger W (2015) Risk assessment of the cultivation of a stacked Bt-maize variety (MON89034 × MON88017) for nematode communities. Soil Biol Biochem 91, 109–118.

Höss S, Menzel R, Gessler F, Nguyen HT, Jehle JA, Traunspurger W (2013) Effects of insecticidal crystal proteins (Cry proteins) produced by genetically modified maize (Bt maize) on the nematode Caenorhabditis elegans. Environ Pollut 2013, 178:147–151.

Höss S, Reiff N, Nguyen H T, Jehle J A, Hermes H, Traunspurger W (2014) Small-scale microcosms to detect chemical induced changes in soil nematode communi-ties – Effects of crystal proteins and Bt-maize plant material. Sci Total Environ, 472, 662–671.