Transgenic approaches to crop improvement.

Transgenic crops are now grown commercially on several million hectares, principally in North America. To date, the predominant crops are maize (corn), soybean, cotton, and potatoes. In addition, there have been field trials of transgenics from at least 52 species including all the major field crops, vegetables, and several herbaceous and woody species. This review summarizes recent data relating to such trials, particularly in terms of the trends away from simple, single gene traits such as herbicide and insect resistance towards more complex agronomic traits such as growth rate and increased photosynthetic efficiency. Much of the recent information is derived from inspection of patent databases, a useful source of information on commercial priorities. The review also discusses the time scale for the introduction of these transgenes into breeding populations and their eventual release as new varieties.