Despite the commercial approval of twenty-five transgenic crops in the U.S. as of mid-1996, concern is still being expressed regarding the potential risks associated with genetically engineered crops. One recurring issue is the possibility of pollen-mediated escape of engineered genes into populations of crop wild relatives. To address this concern, the scientific community has depended on literature on pollen dispersal generated from non-transgenic organisms. Utilization of this information requires the assumption that the pollen mediated movement of native and transgenes is the same. To test the validity of this assumption, we directly compared the pollen-mediated gene movement of native and engineered marker genes using melon plants (Cucumis melo L.) expressing dominant morphological and transgenic traits. Movement into both contiguous border plots and non-contiguous satellite plots were monitored. Dispersal of the native gene and transgene into the satellite plots was identical. Dispersal of the two traits into the plot borders was nearly identical. Of the nearly 4600 seedlings screened for both morphological (presence of green vs. virescent cotyledons) and transgene movement (presence of NPT II protein by ELISA), in no case was the NPT II gene observed in the absence of green cotyledons. However, 39 seedlings were green but did not express NPT II as measured by ELISA. PCR analysis revealed transgene inactivation as a cause of the NPT II ELISAO- seedlings.
Bibliographical noteFunding Information:
We thank Perry Nugent (USDA Vegetable Laboratory, Charleston, SC) for providing the C879-J2 virescent mutant seed and Walter Pett (Entomology Department, Michigan State University) for providing bee hives used in these experiments. We also thank Sue Hammar for assistance with the DNA analysis, Pete Callow, Dan Prince and Karen Hokanson for help with the field experiments, Camille Ciesliga for greenhouse work and all of the aforementioned for melon seed extraction. This work was in part supported by grants from the Consortium for Plant Biotechnology Research (No. 92-34190-6941), the Asgrow and Pioneer Seed Companies, the Office of Agriculture and Food Security Bureau for Global Programs, Field Support and Research, U.S. Agency for International Development under Cooperative Agreement No. DAN 4197-A-00-1126-00. The opinions expressed herein are those of the authors and do not necessarily reflect the views of the U.S. Agency for International Development. Acknowledgement is also made to the Michigan Agricultural Experiment Station for their support of this research.
- Cucumis melo
- Gene movement
- Gene silencing
- Pollen flow
- Risk assessment
- Transgenic plants