Field Evolved Resistance to Bt Proteins

Scientists from the University of Arizona (UA) led by Bruce Tabashnik, a renowned entomologist, published a paper in Nature Biotechnology on the possibility of cotton bollworm/corn earworm (Helicoverpa zea) gaining resistance to the Bt toxins contained in transgenic Bt cotton and Bt corn. An article, authored by a team of international researchers and published on this month's issue of the journal, ‘questions' the conclusion of Tabashnik and colleagues.

Moar and colleagues noted that the UA researchers' definition of Bt resistance "is purely laboratory based, whereas field efficacy and larval survival on plant tissues are the ultimate criteria for contextualizing laboratory-based estimates of resistance". They further explained that the larval samples should not be collected from Bt crops because they will not be representative of the population as a whole, especially for highly mobile insects such as the cotton bollworm. The researcher also questioned the values used to measure resistance, which according to them will introduce artifacts into the analysis.

The paper available at http://dx.doi.org/10.1038/nbt1008-1072

Tabashnik and colleagues, in a separate article, responded to these questions. They provided additional evidences to show that the field-evolved resistance documented with laboratory diet bioassays is associated with increased survival on Bt cotton leaves and control problems in the field.

Read their paper at http://dx.doi.org/10.1038/nbt1008-1074