No detection of Cry1Ac protein in soil after multiple years of transgenic Bt cotton (Bollgard) Use
Authors: Head, G., Surber, J.B., Watson, J.A., Martin, J.W., Duan, J.J.
Journal, Volume, Year: Environmental Entomology, volume 31(1): 30-36, 2002
Soil samples were collected from six different sites that had grown Bollgard (Cry1Ac) cotton for 3-6 years and negative control sites that were either non-cultivated or planted to non-Bt cotton. Samples were collected 3 months post-tillage. Analyzed soil samples using both ELISA and bioassay (Heliothis virescens). Bt was not detected in any field samples. Indicated that the soil was not biologically active toward Heliothis.
The ELISA methods need much improvement and are not as valuable as the bioassay. Extraction efficiency for ELISA was very poor (avg. about 32%) and detection limit of the method was about 12 ng protein/g soil. Detection limit for bioassay was 8 ng/g. Due to some published records that the half-life of protein in soil is short, study should have performed analysis of soil at short time after tillage and the later date that was performed in the study. Gives incomplete picture of environmental fate.