Transgene transfer to wild relatives of crop plants: Invasiveness concepts for novel traits and new habitats.
Letourneau, Deborah*,1, Hagen, Joy1, 1 University of California, Santa Cruz, CA, USA
ABSTRACT- Since the 1980s ecologists have favored an introduced species model for evaluating potential environmental effects of genetically engineered organisms. We examine the extent to which invasion theory can predict which organisms and traits are of relatively more concern, and which environments are likely more invasible. For GE crops, the introduction of genes that confer novel forms of pest resistance for crop protection are under scrutiny for risks associated with increased fitness, competitive ability, and invasiveness of wild crop relatives that may obtain the trait through gene flow. Crops transformed with genes derived from the bacterium Bacillus thuringiensis (Bt) to express insecticidal proteins are now the most common genetically engineered organisms in the environment. In California, Bt-cabbage and Bt-broccoli have been developed for resistance to lepidopteran pests and field-tested. We examine their wild relatives in different habitats in terms of predictions from invasion theory. To test potential effects of a lepidopteran resistance trait in three different environments, we protected, with frequent Bt sprays, 4 wild radish and 4 wild mustard plants at each of 30 sites in each of three growing conditions, and added a caterpillar monthly to 4 other plants, sprayed with denatured Bt spray. Preliminary analyses show that lepidopteran exclusion resulted in a 16% reduction in plant damage by herbivores, on average, for both radish and mustard. Seedling mortality was significantly reduced in Bt spray plots of mustard, but not of radish. Changes in plant fitness of wild mustard and radish when protected from lepidopteran herbivory, and among habitats (cultivated fields, agricultural field margins, and naturally occurring vegetation) can be projected demographically and relative invasibility compared using matrix models.
Key words: invasion theory, genetically engineered crops, transgene, plant fitness
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