Transgenic corn expressing Bacillus thuringiensis (Bt) toxins to control either corn borers or corn rootworms are among the main transgenic crops worldwide. So far rather few studies have reported the effects of transgenic Bt corn on the soil ecosystem. As the decomposer food web has a primary role in determining the mineralization of nutrients in soil, and hence plant nutrient acquisition and plant productivity, it is important to investigate how the introduction of transgenic plants will influence soil decomposition processes.
Four Bt corn varieties are used in our experiments: one sweet corn and two field corn varieties expressing the Cry1Ab toxin against Ostrinia nubilalis (Lepidoptera: Pyralidae), and one field corn variety expressing the Cry3Bb1 toxin against Diabrotica spp. (Coleoptera: Chrysomelidae). We have used litter bags, pitfall traps and wood boards to sample the macoinvertebrate fauna. These methods will maximize the probability that we can detect species that are exposed to Cry toxins and integrate lower trophic level effects. So far, we have found adult and immature earthworms, isopods, diplopods, phalangiids, and some carabids associated with the wood boards. We have found carabids, elaterids, mites, springtails, dipteran and coleopteran larvae, and earthworms associated with the other sampling methods. In the future we will report on species that are exposed and potentially affected by the Cry toxins in the field.
Keywords: soil organisms, risk assessment
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