TA5 Soil Ecotoxicology and Risk Assessment
203 Oregon Ballroom
8:00 AM - 12:00 PM, Tuesday
() Development of subacute bioassays for the assessment of transgenic corn (Zea mays) expressing Bt proteins.
Clark, B1, Coats, J1, 1 Iowa State University, Ames, IA, USA
ABSTRACT- In the last six years, the use of transgenic crops expressing Bt (Bacillus thuringiensis) delta-endotoxins has increased substantially, but assessment of ecological risks from plant-produced Bt suffers from a lack of studies that examine soil biota in an ecologically relevant manner. The goal of the current study is to develop assays that simulate exposure in the agroecosystem and incorporate chronic endpoints. Four bioassays were performed using invertebrate decomposers fed transgenic plant material from two varieties of Bt corn, Bt 11 and Mon 810, and the isolines of each. In a 28-day test, no statistical differences between corn types were observed in survival or population growth of springtails (Folsomia candida). In a 21-day survival and growth test with juvenile earthworms (Eisenia fetida), no statistical differences between corn types were observed. Survival and growth of juvenile pillbugs (Armadillidium sp.) were measured in a 49-day test. Individuals fed Bt 11 had a significantly greater percentage weight increase than those fed its isoline. The results indicate that nutritional differences between the corn types may account for observed growth differences. Further studies are currently ongoing utilizing one additional variety of both Bt 11 and Mon 810, and the nearest isoline of each. Results of a current survival and growth test with juvenile sowbugs (Porcelio scaber) will also be reported. Attempts are made to correlate nutritional content of the food types to the observed results.
Key words: isopod, Bacillus thuringiensis, transgenic, agroecosystem