New York, Oct 27 : As the debate over the safety of genetically modified food continues to rage, biologists have found that GM squash plants - resistant to three major viral diseases -
became more vulnerable to a fatal bacterial infection.

"Cultivated squash is susceptible to a variety of viral diseases and that is a major problem for farmers," said Andrew Stephenson, Penn State University (PSU) biology professor, who led the
study. "Infected plants grow more slowly and their fruit becomes misshapen."

In the mid-1990s, the US 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. "That could impact the biodiversity of plant communities where wild squash are native."

Stephenson and colleagues James A. Winsor, professor of biology, Matthew J. Ferrari, research associate and Miruna A. Sasu, doctoral student, all at PSU, crossed the genetically modified
squash with wild squash native to the southwestern US.

Unlike a lab experiment, the researchers tried to mimic a real world setting during their three-year study.

The researchers then looked at the effects of the virus-resistant transgenes on prevalence of the three viral diseases, herbivory by cucumber beetles, as well as the occurrence of bacterial wilt
disease that is spread by the cucumber beetles.

"When the cucumber beetles start to feed on infected plants they pick up the bacteria through their digestive system," explained Sasu.

"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."

"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."

"Wild and transgenic plants had the same amount of damage from beetles before viral diseases were prevalent in our fields," said Stephenson.

"Once the virus infected the wild plants, the transgenic plants had significantly greater damage from the beetles," he added, according to a PSU release.

These findings appeared in the Tuesday edition of the Proceedings of the National Academy of Sciences.   (IANS)