Environmental impact of genetically modified crops.

Chapter 16 (Page no: 344)

Monitoring Bt resistance in the field: China as a case study.

China was the first country to commercialize biotech crops with the commercialization of tobacco in the early 1990s. In 1997, it formally approved the commercialization of Bt cotton. Despite the availability of local cotton varieties expressing Bacillus thuringiensis (Bt), Monsanto's Bt cotton varieties were also introduced. The adoption of Bt cotton increased consecutively for the first 7 years and from 2004 to 2007 occupied more than 66% of the national total cotton acreage. More than 8 million smallholder, resource-poor cotton farmers derived significant productivity, economic, environmental, health and social benefits, including a substantial contribution to the alleviation of poverty in some areas, as a result of higher incomes from Bt cotton. In most regions, typical cotton farms are on a small scale. Cotton bollworm (CBW) Helicoverpa armigera (Hübner) is the major target insect of Bt cotton. Due to the growing of Bt cotton, in 2003 there was a reduction of more than 95,000 t of pesticide. As an important component of the monitoring programme, baseline Cry1A(c) susceptibility data for the CBW were established; the timing of this coincided with the commercialization of Bt cotton. A systematic monitoring programme for CBW resistance to Bt cotton has been carried out and, to date, no field resistance has been detected. A refuge-based strategy has been employed in resistance management. Natural refuges have successfully been adopted in the Yellow River region, the largest cotton cropping area where mixed cropping with a wide variety of crops, such as maize, soybean, groundnut, oilseed rape, legumes, etc., is generally practised by the small farms. Non-Bt cotton refugia have been recommended in the Changjiang (Yangtse) River region and the North-western region since cotton is the sole host plant for pink bollworm (Pectinophora gossypilla (Saunders)) in the Changjiang River region.

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