Insect bioassay for determining soil degradation of Bacillus thuringiensis subsp. kurstaki CryIA(b) protein in corn tissue.
Sims, S.R. and Holden, L. R.
Environmental entomology. Vol: 25 Issue: 3 Pages: 659-664.
1996
บทคัดย่อ
A bioassay using larval growth inhibition of Heliothis virescens (F.) was used to study the environmental fate (=soil degradation) of Bacillus thuringiensis subsp. kurstaki CryIA(b) protein in transgenic corn plant tissue (transgenic corn). Transgenic corn was incubated for up to 43 d, with and without contact with soil, in a chamber maintaining warm (24-27 degrees C) and humid (>80% RH) conditions. Incubation was terminated by moving the transgenic corn to -80 degrees C. A series of dilutions was made from each incubated sample, mixed into artificial insect diet, and fed to neonate H. virescens. Weights of treated larvae were scored after 7 d growth at approximately 28 degrees C, and the bioactivity of CryIA(b) protein in the samples was determined using regression analysis of the dose-weight response data. The insect bioassay approach allowed for nearly complete recovery of CryIA(b) protein bioactivity in a transgenic corn + soil matrix or transgenic corn incubated without soil contact. CryIA(b) protein added to soil as a component of transgenic corn tissue had an estimated DT50 (50% dissipation time = 'half-life') of 1.6 d and a DT90 (90% dissipation time) of 15 d. CryIA(b) protein in transgenic corn tissue incubated without soil contact, had an estimated DT50 of 25.6 d and a DT90 of 40.7 d. The results suggest that CryIA(b) protein, as a component of postharvest transgenic corn plants, will dissipate readily on the surface of, or cultivated into, soil.