GM crops no longer safe from pests

June 21st, 2012 - 1:24 pm ICT by IANS  

Washington, June 21 (IANS) Genetically modified (GM) crops may no longer be safe from the scrouge of pests, underscoring the importance of closely monitoring and countering pest resistance to biotech crops, according to a new discovery.

Cotton and corn have been genetically engineered to produce toxins derived from the bacterium Bacillus thuringiensis, or Bt, in order to minimise use of broad spectrum insecticides, which can be harmful.

Bt toxins kill certain insect pests but are harmless to most other creatures, including humans. These eco-friendly toxins have been used for decades in sprays by organic growers and since 1996 in engineered Bt crops by mainstream farmers, the journal Proceedings of the National Academy of Sciences reports.

Over time, scientists have learned, initially rare genetic mutations that confer resistance to Bt toxins are becoming more common as a growing number of pest populations adapt to Bt crops, according to an University of Arizona statement.

For instance, caterpillars of the cotton bollworm, Helicoverpa armigera, can munch on a wide array of plants before emerging as moths. This species is the major cotton pest in China, where the study was carried out.

Bruce Tabashnik, head of the department of entomology at the University of Arizona College of Agriculture and Life Sciences, who co-authored the study, considers the findings an early warning to farmers, regulatory agencies and the biotech industry.

“Scientists expected the insects to adapt, but we’re just finding out now how they’re becoming resistant in the field,” Tabashnik said.

To avoid surprises, researchers have exposed cotton bollworm populations to Bt toxins in controlled lab experiments and studied the genetic mechanisms by which the insects adapt.

“We found exactly the same mutation in the field that was detected in the lab,” Tabashnik said. “But we also found lots of other mutations, most of them in the same gene and one in a completely different gene.”

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