Bacillus thuringiensis (Bt) transgenic crop:: An environment friendly insect-pest management strategy

Introduction of DDT (dichloro-diphenyl-trichloroethane) and following move towards indiscriminate use of synthetic chemical insecticides led to the contamination of water and food sources, poisoning of non-target beneficial insects and development of insect-pests resistant to the chemical insecticides. Increased public concerns about the adverse environmental effects of indiscriminate use of chemical insecticides prompted search of alternative methods for insect-pest control. One of the promising alternatives has been the use of biological control agents. There is well-documented history of safe application of Bt (B. thuringiensis, a gram positive soil bacterium) as effective biopesticides and a number of reports of expression of delta-endotoxin gene(s) in crop plants are available. Only a few insecticidal sprays are required on Bt transgenic crops, which not only save cost and time, but also reduce health risks. Insects exhibit remarkable ability to develop resistance to different insecticidal compounds, which raises concern about the unsystematic use of Bt transgenic technology also. Though resistance to Bt products among insect species under field conditions has been rare, laboratory studies show that insects are capable of developing high levels of resistance to one or more Cry proteins. Now it is generally agreed that 'high-dose/refuge strategy' is the most promising and practical approach to prolong the effectiveness of Bt toxins. Although many biosafety concerns, ethical and moral issues exist, area under Bt transgenic crops is rapidly increasing and they are cultivated on more than 32 million hectares world over Even after reservation of European Union (EU) for acceptance of geneticaly modified(GM) crops, 6 out of 25 countries have already adopted Bt crops and many other industrial countries will adopt Bt transgenic crops in near future. While the modem biotechnology has been recognized to have a great potential for the promotion of human well-being, adoption of boisafety protocol is necessary to protect human health and environment from the possible adverse effects of the products of genetic engineering. The debate between proponents and opponents of GM technology has created major obstacles in harnessing benefits of the technology. It has now become clear that transgenics will be accepted by the public only when doubts related with general risks and environmental safety are adequately dispelled. Thus, there is need to organize public awareness and present the benefits of Bt transgenic crops to improve social attitude for their rational deployment. In this review, an attempt has been made to discuss social and environmental safety issues of Bt transgenic crops.