Impacto de algodão geneticamente modificado resistente a insetos sobre a entomofauna de solo

Abstract

Genetic engineering has created genetically modified (GM) varieties of many crops that express the toxin from the bacterium Cry Bacillus thuringiensis Berliner (Bt). The Cry toxin has insecticidal properties, is synthesized during growth of the plant, and can be expressed in any part of it. To evaluate the impact of this technology on the environment, this study aimed to find the effect of GM cotton resistant to insects on the fauna of Formicidae and Coleoptera. The field sample was a commercial area located in the municipality of Maracajú, Mato Grosso do Sul, Brazil. There were two treatments: Bt cotton and non-Bt cotton, and 20 samples were taken in each treatment during the reproductive period of cotton in the 2007/2008 crop season. The samplings were done by interception pitfall traps. It was used the paired t test for each day of collection to compare the occurrence of species in both treatments. Seeking to obtain gradients of community structure of Formicidae and Coleoptera based on species composition, it was used the technique of ordering by hybrid multidimensional scaling (HMDS). The studied Bt cotton area negatively affected the fauna of Formicidae, because of the species richness in Bt cotton was lower when compared to non-Bt cotton, and the species of this family occurred in non-Bt crops were different from those presented in Bt. The fauna of Coleoptera was also affected by Bt crop, as the species that make up the community assessed in Bt crops are different from those that make the non-Bt crop. The fact that negative results were observed regarding the impact on entomofauna in an area with little time under cultivation of Bt cotton, strengthens the possibility of further changes in the long term.