Can Bacillus thuringiensis (Bt) corn residues and Bt-corn plants affect life-history traits in the earthworm Aporrectodea caliginosa?

Bt-corn is genetically engineered to express proteins from the common soil bacterium Bacillus thuringiensis which presents specific toxicity to targeted insect pests. One type of Bt-corn expresses the Cry1Ab protein that provides protection against certain lepidopteran pests, mainly the European corn borer (Ostrinia nubilalis) and the Mediterranean stalk borer (Sesamia nonagroides). Vast areas of agricultural soils worldwide are grown with transgenic Bt-corn. With such widespread use of Bt-corn, it is important to evaluate the potential risks of Bt-protein to non-target organisms in agro-ecosystems such as earthworms. In this study, we investigated the effects of Bt-corn on important life-history traits (survival, reproduction and growth) of the earthworm Aporrectodea caliginosa under various experimental conditions. Finely ground Bt-corn leaves added to soil had no deleterious effects on survival, growth, development or reproduction in A. caliginosa, even in high concentrations that could be considered as a worst-case scenario. Also, growth of juvenile A. caliginosa was unaffected when worms were kept in pots with a growing Bt-corn plant. Only when considering cocoon hatchability did we see a slight, but statistically significant, negative effect of Bt-corn residues. The implications of these results for risk assessment of Bt-corn are discussed.

[1]  Deepak Saxena,et al.  Bacillus thuringiensis (Bt) toxin released from root exudates and biomass of Bt corn has no apparent effect on earthworms, nematodes, protozoa, bacteria, and fungi in soil , 2001 .

[2]  Clive A. Edwards,et al.  Biology and Ecology of Earthworms , 1995 .

[3]  H. R. Whiteley,et al.  Insecticidal crystal proteins of Bacillus thuringiensis. , 1989, Microbiological reviews.

[4]  M. Allen,et al.  Characteristics of macroporosity in a reduced tillage agroecosystem with manipulated earthworm populations: Implications for infiltration and nutrient transport , 1997 .

[5]  T. Gunnarsson,et al.  Effects of metal pollution on the earthwormdendrobaena rubida (Sav.) in acidified soils , 1986, Water, Air, and Soil Pollution.

[6]  T. G. Piearce,et al.  Earthworms, Their Ecology and Relationships with Soils and Land Use. , 1987 .

[7]  J. Weeks,et al.  Recommendations of the 3rd International Workshop on Earthworm Ecotoxicology, Aarhus, Denmark, August 2001. , 2004, Ecotoxicology and environmental safety.

[8]  A. Hilbeck,et al.  Effects of transgenic Bt corn litter on the earthworm Lumbricus terrestris , 2003, Molecular ecology.

[9]  M. Holmstrup.  Sensitivity of life history parameters in the earthworm Aporrectodea caliginosa to small changes in soil water potential , 2001 .

[10]  Graham P. Head,et al.  No Detection of Cry1Ac Protein in Soil After Multiple Years of Transgenic Bt Cotton (Bollgard) Use , 2002 .

[11]  A. Hilbeck,et al.  Degradation of the Cry1Ab protein within transgenic Bacillus thuringiensis corn tissue in the field , 2003, Molecular ecology.

[12]  G. Weesies,et al.  Earthworm populations and species distributions under no-till and conventional tillage in Indiana and Illinois , 1997 .

[13]  P. Krogh,et al.  Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 4. The influence of salt speciation, soil type, and sewage sludge on toxicity using the collembolan Folsomia fimetaria and the earthworm Aporrectodea caliginosa as test organisms , 2001, Environmental toxicology and chemistry.

[14]  D. Saxena,et al.  Transgenic plants: Insecticidal toxin in root exudates from Bt corn , 1999, Nature.

[15]  B. Hansen.  Determination of nitrogen as elementary N, an alternative to Kjeldahl. , 1989 .

[16]  E. Gregorich,et al.  Detection and decay of the Bt endotoxin in soil from a field trial with genetically modified maize , 2003 .

[17]  C.A.M. van Gestel,et al.  A summary of eleven years progress in earthworm ecotoxicology. , 2003 .

[18]  M. Holmstrup,et al.  The relationship between temperature and cocoon incubation time for some Lumbricid earthworm species , 1991, Pedobiologia.