A transgene-centered approach to the biosafety of transgenic phosphinothricin-tolerant plants

The microbial bar and pat genes confer tolerance to the non-selective herbicide phosphinothricin (PPT; sold as Basta or Finale). This tolerance in plants could provide an environmental gain compared to current-day herbicide cocktails, but the safety of such a transgene approach is questioned by many. The biosafety of the presence of these herbicide tolerance genes in plants is evaluated in a ‘transgene-centered approach’. Potentially, the introduction of transgenic PPT-tolerant crops could result in acquired PPT tolerance in weedy relatives of these crops. Assuming responsible use of this trait in agronomy, the ecological consequences with respect to weediness or spread of the transgenic PPT tolerance are concluded to be negligible. The key issue for the toxicological evaluation is whether or not the plant has actually been sprayed with PPT. Consumption of the gene and/or gene product from unsprayed transgenic plant material will not have adverse effects. In case of PPT-sprayed material, PPT or its derivatives could be present in food and feed and crop-specific metabolites might be formed. To date, the toxicological impact of such a putative exposure is not sufficiently clear, and further premarket testing is recommended.