Abstract
Genetically modified, insect-resistant Bacillus thuringiensis (Bt) cotton is cultivated extensively in Pakistan. Past studies, however, have raised concerns about the prevalence of Bt cotton varieties possessing weak or nonperforming insect-resistance traits conferred by the cry gene. We examine this issue using data drawn from a representative sample of cotton-growing households that were surveyed in six agroclimatic zones spanning 28 districts in Pakistan in 2013, as well as measurements of Cry protein levels in cotton tissue samples collected from the sampled households’ main fields. The resultant dataset combines information from 593 sampled households with corresponding plant tissue diagnostics from 70 days after sowing, as well as information from 589 sampled households with corresponding diagnostics from 120 days after sowing. Our analysis indicates that 11 percent of farmers believed they were cultivating Bt cotton when, in fact, the Cry toxin was not present in the tested tissue at 70 days after sowing (i.e., a Type I error). The analysis further indicates that 5 percent of farmers believed they were cultivating non-Bt cotton when, in fact, the Cry toxin was present in the tested tissue (i.e., a Type II error). In addition, 17 percent of all sampled farmers were uncertain whether or not they were cultivating Bt cotton. Overall, 33 percent of farmers either did not know or were mistaken in their beliefs about the presence of the cry gene in the cotton they cultivated. Results also indicate that toxic protein levels in the plant tissue samples occurred below threshold levels for lethality in a significant percentage of cases, although these measurements may also be affected by factors related to tissue sample collection, handling, storage, and testing procedures. Nonetheless, results strongly suggest wide variability both in farmers’ beliefs and in gene expression. Such variability has implications for policy and regulation in Pakistan’s transgenic cotton seed market.
Highlights
Modified, insect-resistant Bacillus thuringiensis (Bt) cotton was officially released in Pakistan in 2010 when the National Biosafety Committee (NBC), operating under the auspices of the Pakistan Environmental Protection Agency (EPA), approved commercialization of nine Bt cotton varieties containing first-generation cry genes that confer resistance to Lepidopteran pests
Since the strip test results reported here are based only on tissue samples taken from plants in each farmer’s main cotton plot, it is impossible to use these data to measure the intensity at which Bt cotton was cultivated on an entire farm or the extent to which seed mixing, variety or trait diversification, or refugia strategies might explain the presence of both Bt and non-Bt cotton
The data do suggest that intentional strategies in which farmers plant multiple varieties are relatively rare, thereby ruling out risk management or refugia strategies as an explanation of the discrepancies between farmers’ reported cultivation of Bt cotton in their main plots and our test results
Summary
Modified, insect-resistant Bacillus thuringiensis (Bt) cotton was officially released in Pakistan in 2010 when the National Biosafety Committee (NBC), operating under the auspices of the Pakistan Environmental Protection Agency (EPA), approved commercialization of nine Bt cotton varieties containing first-generation cry genes that confer resistance to Lepidopteran pests. The gene is effective in controlling certain types of Lepidopteran pests such as American bollworm (Helicoverpa zea), old world bollworm (Helicoverpa armigera), pink bollworm (Pectinophora gossypiella), spiny bollworm (Earias spp.), and tobacco budworm (Heliothis virescens). It is less effective, against cotton leafworm (Spodoptera litura) and fall armyworm (Spodoptera frugiperda), resistance has emerged in some countries (e.g., pink bollworm [10]). By reducing losses from bollworm damage, Bt cotton has become an important damage abatement technology in major cotton-producing countries worldwide
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