Herbicide-tolerant crops-real farmer opportunity or potential environmental problem?

Classical breeding, in-vitro selection and genetic engineering techniques have produced herbicide-tolerant crops. Commercial adoption of these cultivars in North America provides tolerance predominantly to non-selective herbicides for novel weed-control strategies. Of special value is the integration of these crops in minimum tillage situations, maintaining of a wide range of herbicides with different modes of action to provide a variety of opportunities for weed-control management. Associated with these special crops are a series of environmental issues which at present limit the rate of commercial development in Europe. Unlike the successful performance of herbicide tolerance in the crops, these strategic issues are much more difficult to resolve for technical, political, ethical and moral reasons. The primary concerns are the feasibility of controlling the volunteer crop and the opportunity for indiscriminate introgression of the herbicide-tolerance gene into agricultural and natural ecosystems. It is unlikely that these questions will be resolved without scaling-up field experiments to include the detection of herbicide-tolerance genes. The economic and management implications of herbicide-tolerant crops require special consideration in view of the necessity to integrate conventional and transgenic crops in new cropping systems.