Development of methods to assess the fate and effects of Bacillus thuringiensis (Bt) Cry1F and Cry3Bb1 proteins

Biotech crops expressing Bacillus thuringiensis (Bt) insecticidal crystalline (Cry) proteins became commercially available in the US in 1996. In 2006, 19 million ha of Bt corn were planted worldwide, which resulted in a significant reduction in the amount of chemical insecticides that are necessary to control agricultural pests. Despite the high adoption rates of this novel insecticide, little is known about the aquatic fate of transgenic Bt proteins and their non-target effects on aquatic invertebrates despite several potential routes of transport to aquatic systems. Methods were developed to investigate the aquatic fate of transgenic Bt proteins and to determine their potential effects on non-target aquatic invertebrates. Laboratory microcosms containing pond water only, as well as pond water and sediment were used to examine the fate of the coleopteran-active Bt Cry3Bb1 protein in decomposing MON 863 corn leaf, stalk, and root. A half-life of less than three days was found for Bt Cry3Bb1 from MON 863 corn residue. No Bt Cry3Bb1 was measured in the pond water or sediment extracts of microcosms containing MON 863 corn. In an acute, static, partialrenewal toxicity test, Bt Cry3Bb1 protein from MON 863 root extracts was fed to Chironomus dilutus larvae for ten days. A statistically significant (p < 0.05) decrease in C. dilutus survival at nominal concentrations of 30 ng/mL was found, however, no effect on growth among the surviving larvae was observed.