Scientists Discover Genetic Basis of Pest Resistance to Biotech Cotton

A field planted with Bt cotton in Southern Arizona. (Photo credit: Timothy Dennehy)
A field planted with Bt cotton in Southern Arizona. (Photo credit: Timothy Dennehy)

An international team led by scientists at the University of Arizona and the U.S. Department of Agriculture has discovered what happens on a molecular basis in insects that evolved resistance to genetically engineered cotton plants.

The findings, reported in the May 19 issue of the journal PLOS ONE, shed light on how the global caterpillar pest called pink bollworm overcomes biotech cotton, which was designed to make an insect-killing bacterial protein called Bt toxin. The results could have major impacts for managing pest resistance to Bt crops.

Caterpillars of the pink bollworm are one of the most detrimental pests to cotton production worldwide. First detected in the U.S. in 1917, this invasive insect species wreaked havoc on Arizona's cotton-growing industry, with larvae infesting as many as every other cotton boll (the fruit capsule containing the valuable fibers).

A breakthrough came in 1996 with the introduction of Bt cotton, a genetically engineered crop containing a gene transferred from the bacterium, Bacillus thuringensis, endowing the plants with a protein that kills some, but not all insects. Organic growers have used Bt proteins in sprays for decades because they kill certain pests but are not toxic to people and most other organisms. Pest control with Bt proteins – either in sprays or genetically engineered crops – reduces reliance on chemical insecticides. Although Bt proteins provide environmental and economic benefits, these benefits are cut short when pests evolve resistance.

"Bt crops have had major benefits for society," said Jeffrey Fabrick, the lead author of the study and a research entomologist at the USDA Agricultural Research Service in Maricopa, Arizona. "By understanding how insects adapt to Bt crops we can devise better strategies to delay the evolution of resistance and extend these benefits."

"Many mechanisms of resistance to Bt proteins have been proposed and studied in the lab, but this is the first analysis of the molecular genetic basis of severe pest resistance to a Bt crop in the field," said Bruce Tabashnik, one of the paper's authors and the head of the Department of Entomology in the UA College of Agriculture and Life Sciences. He also is a member of the UA's BIO5 Institute.

Check out the rest of this May 2014 UANews article at the link below.

Based on laboratory experiments aimed at determining the molecular mechanisms involved, scientists knew that pink bollworm could evolve resistance against the Bt toxin, but they had to go all the way to India to observe this happening in the field.

Date released: 
May 28 2014
Contact: 
Bruce Tabashnik