Modified crops reveal hidden cost of resistance

Penn State Live: Genetically modified squash plants that are resistant to a debilitating viral disease become more vulnerable to a fatal bacterial infection, according to biologists. "Cultivated squash is susceptible to a variety of viral diseases and that is a major problem for farmers," said Andrew Stephenson, Penn State professor of biology. "Infected plants grow more slowly and their fruit becomes misshapen."

In the mid-1990s, the U.S. Department of Agriculture approved genetically modified squash, which are resistant to three of the most important viral diseases in cultivated squash. However, while disease-resistant crops have been a boon to commercial farmers, ecologists worry there might be certain hidden costs associated with the modified crops.

"There is concern in the ecological community that, when the transgenes that confer resistance to these viral diseases escape into wild populations, they will (change) those plants," said Stephenson, whose team's findings appear today (Oct. 26) in the Proceedings of the National Academy of Sciences. "That could impact the biodiversity of plant communities where wild squash are native."

…The researchers discovered that as the viral infection swept the fields containing both genetically modified and wild crops, the damage from cucumber beetles is greater on the genetically modified plants. The modified plants are therefore more susceptible to the fatal bacterial wilt disease.

…"Our study has sought to uncover the ecological cost that might be associated with modified plants growing in the full community of organisms, including other insects and other diseases," said Ferrari. "We have shown that while genetic engineering has provided a solution to the problem of viral diseases, there are also these unintended consequences in terms of additional susceptibility to other diseases."…

Cucumber beetles on squash flowers. Shot by Miruna Sasu, Penn State