Detection and decay of the <i>Bt</i> endotoxin in soil from a field trial with genetically modified maize
Why this work is in the frame
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Bibliographic record
Abstract
Summary Genetically modified plants and their residues may have direct effects on ecosystem processes. We aimed to determine the amount in soil of the insecticidal δ‐endotoxin, originally from the bacterium Bacillus thuringiensis , introduced into soil by root exudates and residues from genetically modified maize, to compare the short‐term rates of decay of Bt ‐maize and non‐ Bt ‐maize, and to determine the rate at which the toxin in Bt ‐maize leaves decomposes in soil. Intact soil, size fractions of soil, soluble fractions from soil and fractions of organic residues from a field where Bt ‐maize had been cultivated for 4 years were analysed for the Bt δ‐endotoxin. Traces of the δ‐endotoxin were detected in the whole (unfractionated) soil, the water‐soluble fractions, and some of the particle‐size fractions, but it was sufficiently concentrated only in the > 2000‐µm size fraction to be quantified. The δ‐endotoxin concentrations in this fraction ranged between 0.4 and 4.4 ng toxin g −1 fraction, which equated to 70, 6 and 50 mg toxin m −2 in the 0–15, 15–30 and 30–60 cm depths, respectively (or 126 mg toxin m −2 over the 0–60 cm depth) in the field in June (early summer). The > 2000‐µm size fraction was a mixture of light‐ and dark‐coloured organic material and mineral material comprising sand grains and stable aggregates. For samples collected early in the growing season, most of the detected δ‐endotoxin was present in the light‐coloured organic material, which was comprised of primarily live roots. However, recognizable maize residues, probably from previous years' crops, also contained δ‐endotoxin. In a laboratory incubation study, Bt‐ and non‐ Bt‐ maize residues were added to soil and incubated for 43 days. There was no detectable difference in the decomposition of plant material from the two lines of maize, as determined by CO 2 production. The quantity of δ‐endotoxin in the decomposing plant material and soil mixtures declined rapidly with time during the incubation, with none being detectable after 14 days. The rapid disappearance of the δ‐endotoxin occurred at a rate similar to that of the water‐soluble components of the maize residues. The results suggested that much of the δ‐endotoxin in crop residues is highly labile and quickly decomposes in soil, but that a small fraction may be protected from decay in relatively recalcitrant residues.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it