Soil inactivation of the Bacillus thuringiensis subsp. kurstaki CryIIA insecticidal protein within transgenic cotton tissue: Laboratory microcosm and field studies
Authors: Sims, S.R., Ream, J.E.
Journal, Volume, Year: Journal of Agricultural and Food Chemistry, volume 45:1502-1505, 1997
The fate of Bt subspecies kurstaki CryIIA was studied through field and laboratory incubation of soil (dupo loam) with incorporated Bt-containing cotton plant material. The study was evaluated by determining the reduction in the bioactivity of the protein in H. virescens growth-reduction bioassay. A DT50 of 15.5 days was found in the lab and 31.7 days in the field. Rapid reduction in bioactivity was observed during the first 40 days but slowed during the following 80 days.
Bt cotton was added at environmentally relevant levels. Both incubations (lab and field) retained 25% of initial bioactivity at 120 days. Bioassay as an estimate of dissipation time is not very quantitative. It does not show amounts of protein, but does demonstrate activity.