Biological Sciences, School of


Date of this Version

Fall 11-22-2010

Document Type



A dissertation Presented to the Faculty of The Graduate College at the University of Nebraska In partial fulfillment of requirements For the degree of Doctor of Philosophy, Major: Biological Sciences, Under the Supervision of Professor Diana Pilson. Lincoln, Nebraska: 19 November 2010
Copyright © 2010 by Holly R. Prendeville
Chapter 1 is published in the Journal of Applied Ecology 2009, 46, 1088–1096.


Two ecological risks associated with the use of transgenic crops include the effects of transgene products on non-target organisms and the effects of a transgene after it moves from crops into a wild plant population. In work presented here, we specifically investigate the ecological risks of virus-resistant transgenic squash. We observed pollinator behavior to determine if pollinators are affected by nontarget effects of the virus-resistant transgene. We found that pollinator behavior did differ between conventional and virus-resistant transgenic squash due to pleiotropic effects of the transgene. This difference in pollinator behavior can affect plant mating patterns, thereby affecting crop-wild hybridization and transgene introgression into wild squash populations.

For the virus-resistant transgene to confer a benefit in wild squash populations virus must be present. Thus, we surveyed wild squash populations to determine the prevalence of five virus species and members of one virus genus. We found that virus is prevalent in wild squash populations though variable among populations, virus species, and years.

Finally, we focused on the effects of the virus-resistant transgene in wild squash populations. Then, we surveyed wild squash populations for the virus-resistant transgene, which we did not find. Next, we found the population growth rate of wild squash is reduced by virus. However, there is no affect of virus when the virus-resistant transgene is present in wild squash.

We recommend future risk assessments of transgenic crops to examine non-target effects of transgenes on pollinators in different environments as this can affect transgene movement into wild populations. Furthermore, additional wild squash populations should be assayed for the transgene, since our work was not exhaustive. Moreover, to predict when virus affects wild populations, thereby infer when a virus- resistant transgene is favored by natural selection, additional work examining plant-virus ecology is essential. The results from these studies will allow us to better predict the evolution of transgenic resistance in wild populations and guide policy decisions on the use and deregulation of transgenic crops.

Adviser: Diana Pilson