Despite full commercial approval of twelve transgenic crops in the U.S. (circa
1995), concern is still being expressed regarding the potential risks associated with the agronomic-scale production of transgenic crops. One commonly mentioned concern involves the pollen-mediated escape of engineered genes into populations of crop wild relatives. In this study two questions relevant to this issue were investigated: 1) Can plantings of border rows effectively limit pollen mediated gene movement, and 2) Do the pollen-mediated dispersal patterns of transgenes differ from those of native genes?
The ratio of recessive trap plants to wild type donor plants was varied to test the
efficacy of border rows as a means to limit the spread of transgenic pollen to discontiguous satellite plots. Gene movement within the border plots assumed a leptokurtic distribution. Increasing the number of donor plants increased levels of
gene flow both within the border and to the discontiguous satellite plots. As the
trap/donor ratio increased, there was a significant decrease in long distance gene
movement to the satellites, although the observed year to year and site to site
variability could limit the effectiveness of this strategy. Furthermore, extremely large
numbers of border plants would be required to minimize pollen movement on a commercial scale. Dispersal patterns of transgenes and native genes were evaluated by comparing levels of pollen-mediated gene movement from melon plants (Cucumis melo) expressing dominant morphological and transgenic marker genes into a surrounding border of recessive non-transgenic melon plants. Long distance dispersal patterns for the two genes were identical and dispersal patterns into the plot borders were nearly identical. Several of the apparent discrepancies were explained by transgene inactivation, a phenomenon which has implications for any study measuring gene movement with transgenic plants. Results from this study validate the
assumption that native and transgenes have the same dispersal patterns. Thus,
application of non-transgenic results to trans gene escape and dispersal issues should be appropriate. However, the assessment of establishment and spread will depend on both pollen movement and the fitness value of the particular transgene crop combination.
Dissertation completed at the Michigan State University, 1995
Hokanson, Stan C..
Risk Assessment of Transgenic Plants: Evaluation of Border Rows as a Containment Strategy for Transgenic Pollen and a Comparison of Pollen Dispersal Patterns for Native and Transgenes.
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