Risk Assessment and Ecological Effects of Transgenic Bacillus thuringiensis Crops on Non‐Target Organisms^F

Abstract

The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.

Does the transgenic Cry1Ac toxin adversely affect the population dynamics of floral-visiting insects in soybean crop?

“…Currently, available transgenic plants resistant to caterpillars contain genes of the bacterium Bacillus thuringiensis (Bt) that encode lethal toxins for certain insect groups. Bt plants have the potential to minimize losses caused by insect pests, especially the order Lepidoptera, as well as reduce insecticide use (Yu et al, 2011). Bt insecticidal proteins kill insects by a process comprising the following steps: crystal solubilization processing, conversion to an active protoxin form, high-affinity binding to the midgut receptors, irreversible insertion of the toxin into the membrane, and the formation of infection pores (Bravo et al, 2005;de Maagd et al, 2001).…”

Potential of antranilic diamides applied in seeds of soybeans with and without cry1ac protein for Helicoverpa armigera caterpillar control

“…Aside from the fact that they are different genotypes, this is still indicative of the action of Cry1Ac protein on H. armigera. This protein causes a reduction in feeding and, consequently, starvation of larvae by specific binding in the ciliated membranes of the midgut, leading to death (Yu et al, 2011).…”

Application of Box-Behnken Experimental Design to Optimize the Extraction of Insecticidal Cry1Ac from Soil

“…15 In addition to the arguments on the fate of Bt proteins, debates are going on for their ecological risks. 5,16 Although no conclusive decision has been drawn until now, previous studies showed that the residual Bt proteins might adversely affect soil biodiversity due to their toxicity to the invertebrates and microorganisms. 17 Therefore, more studies are needed to understand the fate and risks of soil-associated Bt proteins, and an effective and robust method for analyzing trace amounts of Cry proteins in soil is the premise of these types of research.…”

“…1,3 The widespread planting of Bt crops has raised concerns on their environmental risks. 4,5 Insecticidal Cry proteins produced by Bt crops may be released to soil through roots exudates, tasseling, or plant residues. As a consequence, persistence of Cry proteins in soil become an urgent concern.…”