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Unintended Effects of Genetic Manipulation
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Posted: October 2014

Field Performance of Bt Transgenic Crops: A Review

Chinese scientists from the National Key Laboratory of Crop Genetic Improvement at the Huazhong Agricultural University in China have reviewed the performance of different crops that have been genetically modified to produce an insecticidal protein (“Bt” crops). The authors are proponents of genetic engineering and are interested in finding ways of improving the performance of GM crops.

They review the follow traits:
  • Yield performance
  • Nitrogen assimilation and metabolism
  • Potassium assimilation
  • Optimum population density
The also review findings on:
  • Spatial and temporal expression of the Bt genes
  • Genotypic variation and inheritance of the Bt genes
  • Effects of abiotic factors on transgene expression
The review cites many different studies and highlights the variety of results researchers find. Some examples:
  • Yield in Bt crops is often, but not always, higher under severe pest pressure, while when pest pressure is low, yield is not higher, although farmers are still paying the premium price for the crop protection.
  • Bt and non-Bt cotton have similar yields when farmers spray additional insecticides to kill insects that are not killed by the Bt toxin.
  • Bt crops often require greater planting density to have high yields, but since there are higher harvest costs and higher seed costs for Bt seeds, the higher yields do not necessarily mean higher profits.
The review gives many such examples. Overall it shows how context-dependent and unpredictable the performance of Bt crops is. General, across-the-board claims are therefore misleading.

The review can be accessed free-of-charge online at: http://www.cropj.com/huang_8_1_2014_18_26.pdf.

Source:
Wang, F., S. Peng, K. Cui et al. (2012). “Field Performance of Bt Transgenic Crops: A Review,” Australian Journal of Crop Science vol. 8, pp. 18-26.

Copyright 2014 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/Bt-review_Wang2014.php

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