Research was conducted to determine levels of CrylAc in transgenic Bacillus thuringiensis Berliner (Bt) cotton leaves from four different commonly used bioassays. Significant differences in the amount of CiylAc were found among the different bioassay types. For bioassay arenas that prevented desiccation of leaf material, CrylAc levels remained stable for 10 d after tissue was excised from the plant. In other bioassay types, CrylAc levels increased in excised leaves over time because of desiccation th at concentrated the transgenic protein. We conclude that careful descriptions of bioassay methodology are essential for laboratory studies documenting Cry1Ac levels and corresponding efficacy against lepidopteran pests.
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