Abstract

When field trials of transgenic plants are hampered by practical containment problems, manipulation experiments can uncover the potential consequences of cultivated and wild gene flow. Using Bt Bacillus thuringiensis topical larval spray and larval supplements, we measured the effect on herbivore fitness reduction on Brassica rapa and wild radish Raphanus sativus. These species represent different life histories among potential Bt transgenic recipients from Bt cabbage in the United States and Asia, where rare random mating is expected with high exposure. Protected wild radish and wild mustard seedlings had about half of the herbivore damage compared to exposed plants and a 55% lower seedling mortality rate, resulting in successful reproduction. 27% higher yield, 14 days longer shelf life and 118% more seeds on average. Seed addition experiments in miniature and in situ indicate that wild radish is more contagious than wild radish in coastal grasslands.