Yes, there are cases where a GM crop has not delivered the intended improvements such as increased crop yields or virus resistance. The same problems arise with conventional breeding approaches.
Some of the first GM herbicide-resistant soybean varieties had lower yields than non-GM varieties, in spite of the promise of better yields with better weed control. The new DNA for herbicide resistance was transferred into low yielding varieties that were available when the GM project was started. Some farmers still adopted these GM varieties because they were able to control weeds with less labour and energy than with the conventional variety.
Another crop that has been slow to deliver its promise is GM rice produced for the “Golden Rice” project. This initiative aims to address vitamin A deficiency in some parts of the world by adding genes to the rice to improve its nutritional content. But the first varieties did not work well enough and would not have adequately bolstered vitamin A in the diets of populations needing it. Improved varieties are now undergoing field trials.
A frequent criticism of GM is that it has failed to deliver more than herbicide tolerance, insect resistance and a few examples of disease resistance. This is because these uses are based on genes available 20 years ago. With increasing knowledge of gene function, new GM crops with other characteristics are being developed and some of these are close to becoming available to farmers (see Q17). Of course among these new applications, there are likely to be failures as well as successes.
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