Bt transgenic crops: risks and benefits

摘要

Bt crops, predominantly maize and cotton hybrids, transgenically expressing cry genes derived from Bacillus thuringiensis, were planted on approximately 14 million hectares (worldwide) in 1999. Preliminary reports suggest that in most cases pesticide use was reduced, and in some situations there were significant increases in yields and profits. However, assemblages of secondary pests - such as aphids, plant bugs and thrips - also exist in Bt crops, and although the overall need for scouting and chemical control is reduced in Bt crops, there may be a requirement for additional, conventionally applied chemicals to control such non-target pests. Naturally-occurring Bt toxins with activity against a wide variety of pest species have been discovered and are thus potentially available for engineering into Bt crops to control a broader spectrum of pests than are currently targeted. New Bt crops and second-generation products incorporating an expanding range of Cry toxins and other arthropod targeted genes are in development and could become available for introduction to the market within the next few years.