Genetically-Manipulated "Bt" Plants Produce 1,000 Time More "Bt" Toxin Per Acre
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July 2, 1999
Prof. Joe Cummins
e-mail: jcummins@julian.uwo.ca
Estimates of Bt toxin load in Corn and Potato Genetically Modified as
compared with being Sprayed (with Dipel) Crops such as corn or potato
are being genetically modified (GM) with genes for the Bacillus
thuringiensis (Bt) toxin. It is worth estimating the levels of Bt toxin
produced in GM crops and comparing that estimate with the level of Bt toxin
used with recommended application of a commercial Bt preparation such as Dipel.
Such estimates do not appear have been published previously.
The usual dose of Dipel recommended is 10 lb/acre of 0.5% a/I
formulation of Bt spores containing as much as 20% crystal toxin. About
4.5 grams of crystal toxin is delivered to each acre. The typical Bt
toxin is a protein 150,000 dalton. The preparation contains about 2X10
exp19 toxin molecules per acre. Corn with toxin gene is planted about 22000
plants per acre, each mature plant has greater than 10 exp12 cells. The
average cell produces 1000000 Bt toxin molecules during its life of a
season. This produces 5.5 kg crystal toxin per acre. About 2X10 exp 22
molecules Bt toxin are produced per acre.
GM corn produces at least 1000 times more Bt toxin per acre than does a
heavy Bt application. GM potato is planted at 8000 plants per acre but
produces a greater cell mass than the corn plant. Potatoes are likely to
produce 500 to 1000 times more toxin per acre than that applied as a
Dipel application. Even though application delivers less toxin it controls
insects as effectively as does genetic modification.[Editor
bolding added]
References
Gawron-Burke,C and Baum, J. "Genetic Manipulation of Bacillus
thuringiensis" Genetic Engineering 13,237-63,1991
Baum,J and Malvar,T "Regulation of insecticidal crystal protein
production in Bacillus thuringiensi" Molecular Microbiology 18,1-12,1995
Bacillus thuringiensis kurstaki Cornell University
http://www.biconet.com/biocontrol/btk.htm
http://www.soyinfo.com/haz/bt2.shtml