Natural selection on not-so-natural plants

Stephenson's ongoing research program examines what happens when modified genes, known as transgenes, escape into fields of wild squash. Stephenson is investigating a particular transgene that gives squash plants extra resistance to a virus that commonly infects both wild and cultivated squash. Scientists have long worried that if transgenes like this one escape into the wild, plants with the gene may grow unchecked and wreak havoc on ecosystems.

Stephenson's field experiments, which have been going on for four years now, show that the transgene does help plants resist the target virus. When aphids that carry the virus arrive in experimental fields in the spring, wild plants without the transgene tend to become infected while transgenic plants stay healthy. Good health, however, makes the transgenic squash look tasty to beetles. Beetles preferentially attack transgenic squash, infecting many with devastating bacteria. The beetle attack neutralizes nearly all of the fitness advantage the transgenic squash may have enjoyed by being resistant to viral infection. So in this case, natural selection kept the genetically modified plants in check.

The research is published in the November/December issue of the International Journal of Plant Sciences.