Virus-Resistant GM Squash More Vulnerable to Bacterial Wilt Attack, Study Finds

Squash plants genetically modified to resist viral diseases become more vulnerable to a fatal bacterial infection, researchers at the Pennsylvania State University found. In a three-year study, Andrew Stephenson and colleagues examined the effects of the transgene on fitness, on herbivory by cucumber beetles, on the incidence of mosaic viruses, and on the incidence of bacterial wilt disease.

The researchers found that the fitness advantage enjoyed by virus-resistant plants comes at a price. "Plants that do not have the virus-resistant transgene get the viral disease," explained Stephenson, whose team's work is funded by the National Science Foundation. "However, since cucumber beetles prefer to feed on healthy plants rather than viral infected plants, the beetles become increasingly concentrated on the healthy -mostly transgenic - plants."

Results showed that the prevalence of bacterial wilt disease was significantly greater on transgenic plants than on non-transgenic plants. "When the cucumber beetles start to feed on infected plants they pick up the bacteria through their digestive system," explained Miruna Sasu, co-author of the study published this week in PNAS. "This feeding creates open wounds on the leaves and when the bugs' feces falls on these open wounds, the bacteria find their way into the plumbing of the plant."

The paper is available at http://dx.doi.org/10.1073/pnas.0905106106 For more information, read http://www.environment.psu.edu/news/2009_news/oct_2009/modified_crops.asp