Figure: More than 66,000 pink bollworm caterpillars were tested for this long-term study. (Photo: Wan Peng)

Researchers from the University of Arizona (UA) have discovered an unexpected strategy that can delay, and even reverse, the evolution of resistance by pests to genetically engineered crops. The study, published in the Proceedings of the National Academy of Sciences, reveals that hybridizing genetically engineered cotton with conventional cotton reduced resistance in the pink bollworm, a voracious global pest.

The study is a collaboration between researchers at UA and China, and over 11 years, they tested more than 66,000 pink bollworm caterpillars from China's Yangtze River Valley. The main strategy for delaying resistance is providing refuges of the pests' host plants that do not make Bt proteins. This allows survival of insects that are susceptible to Bt proteins, and also reduces the chances that two resistant insects will mate and produce resistant offspring.

The strategy in China involves interbreeding Bt cotton with non-Bt cotton, crossing the resulting first-generation hybrid offspring, and planting the second-generation hybrid seeds. This process generates a random mixture within fields of 75 percent Bt cotton plants side-by-side with 25 percent non-Bt cotton plants. Bruce Tabashnik, senior author of the study, calls this strategy revolutionary because it was not designed to fight resistance and arose without mandates by government agencies, but emerged from the farming community of the Yangtze River Valley. While previous attention focused on the drawbacks of interbreeding between genetically engineered and conventional plants, the authors point out that the new results demonstrate gains from such hybridization.

For more details, read the news article at the UANews.