Scientists Review Tier-1 Assays Conducted for Bt Crops

Bt crops usually undergo "Tier-1 assays" before commercialization to determine the effects of the crop to non-target organisms. These tests include feeding test organisms with insecticidal proteins from Bt crops in the laboratory. Since the test organisms are directly exposed to higher concentrations of insecticidal proteins than in normal environment, the results of the assays are more conservative than other studies where the test organisms were fed only with plant parts of a Bt crop. Thus, Yun-He Li from the Chinese Academy of Agricultural Sciences and colleagues analyzed existing data from Tier-1 assays in terms of the toxicity of Bt proteins to non-target arthropods.

The researchers focused on three important factors the Tier-1 assays they reviewed: (a) methods for delivery of the Bt protein to the test organisms; (b) the need for and selection of compounds used as positive controls; and (c) methods for monitoring the concentration, stability, and bioactivity of the Bt protein during the assay. Results of their review showed that Bt proteins have no direct toxicity to non-target organisms.

Read the abstract at http://onlinelibrary.wiley.com/doi/10.1111/1744-7917.12044/abstract.