The Limits Of This Technology

The rate at which new transgenic traits can be expected to appear in the near future depends largely on the number of genes encoding them. Traits controlled by single genes, or traits that can be altered or eliminated by the loss of expression through silencing of a single gene or group of related genes, have been the first developed and commercialized. Genetically complex traits probably will require additional years of research to understand them, let alone to express and regulate them in a genetically engineered crop species. Nevertheless, many complex traits, including those controlling adaptation to abiotic stresses such as drought and salinity, flowering and reproduction, and hybrid vigor, are being investigated, and it is possible that some of these traits could appear in transgenic crop plants during the next decade.

The social acceptability of products from transgenic plants has affected and may continue to affect their adoption. Social acceptability has many components, including environmental and human health risks, food choices, the ownership of agricultural inputs and production process, the future structure of agriculture, and so on. This issue is extremely complex and volatile, and it may take several more years before it has stabilized sufficiently so that it will be possible to anticipate how various societies around the world might accept or reject transgenic plants.

Although these and other factors are involved currently in limiting the application of transgenic plants, the central trade-off that may limit it ultimately may involve a classic gene—environment trade-off in crop production. A broadly adapted trait may not be able to be used optimally without a corresponding management system. For example, the short-statured rice varieties of the Green Revolution required an intensive management system oriented around high fertilizer and pesticide use to attain their high yields across vast areas of Asia. These varieties, whether transgenic or conventional, are limited by the applicability of the attendant management system, which creates the environment in which they can flourish. Conversely, a plant with a trait adapted to specific environments associated with a single field or valley would not be broadly applicable to vast growing regions because the environment would not be equally suitable throughout. The scale of use of such locally adapted varieties depends on a system of seed production and distribution that reliably delivers the appropriate seed at the proper time. The system of self-propagated land races admirably meets these needs, but it remains to be seen whether a commercial seed distribution system is able to deliver varieties that are so locally adapted. Finally, as noted above, transgenic plant varieties are being developed for extremely specialized uses on areas of only hundreds of hectares. The scale of use of these specialty varieties will probably depend on how many different such uses are commercially successful as well as the intensivity of management needed to produce them. In conclusion, if technical factors and social acceptance do not limit the adoption of transgenic crops, the costliness of management associated with the specialty transgenic crops, the applicability of management of the broadly adapted transgenic crops, and the delivery of seed of locally adapted transgenic crops likely will limit their applicability, much like conventional varieties are limited today.

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