genetically modified corn— environmental benefits and risks转基因玉米u2014u2014环境效益和风险.pdfVIP

Feature Genetically Modified Corn— Environmental Benefits and Risks Virginia Gewin orn is one of humankind’s earliest innovations. It was Box 1. Bt Technology Cdomesticated 10,000 years ago when humans learned to cross-pollinate Bacillus thuringiensis, a soil bacterium, produces several crystal (Cry) protein toxins that plants and slowly turned a scraggly destroy the gut of invading pests, such as larval caterpillars. So far, over 50 cry genes have nondescript grass called teosinte been identified and found to affect insect orders differently. into plump, productive modern corn Considered safe to humans, mammals, and most insects, Bt has been a popular pesticidal (Figure 1). As needs change, so does spray since the 1960s because it had little chance of unintended effects. Engineering the plant breeding. Today, while biotech gene into corn, however, caused an unexpected public backlash. “We thought it was going super-giants manipulate corn genetics to be the greatest thing since sliced bread,’’ says Guy Cardineau, agricultural biotechnologist to satisfy farmer desires and a global at Arizona State University. “ Here’s a way to withstand insect pressure, eliminate the use of market, indigenous Mexican farmers do pesticides, and Bt spray was widely used in organic agriculture,’’ he adds. The Bt wrangle so to fulfill individual needs. Although illustrates how differently a product and a process can be regarded. the tools differ, the goal remains the After the expensive development process, today’s concern is that broad-scale planting of same—to cultivate desirable traits. Bt corn will render the toxin ineffective over