Abstract Background Transgenic cotton producing toxins derived from the bacterium Bacillus thuringiensis (Bt) is used globally to manage insect pests, including the pink bollworm, Pectinophora gossypiella , one of the most damaging pests of cotton. The use of Bt cotton, which produces either a single Bt Cry toxin (Cry1Ac) or two Cry toxins (Cry1Ac + Cry2Ab), has sustained susceptibility and successfully managed pink bollworm in both China and the United States. In contrast, pink bollworms in India have evolved practical resistance to Bt cotton producing Cry1Ac or Cry1Ac + Cry2Ab. Recent studies suggest that pink bollworm may have similarly evolved resistance to transgenic Bt cotton in neighboring Pakistan. Results Field trials of non-Bt cotton, four Cry1Ac Bt cotton varieties, and six Cry1Ac + Cry2Ab Bt cotton were assessed for pink bollworm infestation and damage in Pakistan in 2020 and 2021. High levels of infestation in flowers and bolls, as well as cotton seed yield loss were observed in all the tested cultivars. Only one Bt cultivar producing Cry1Ac + Cry2Ab (MNH-1045) showed a significant reduction in pink bollworm infestation and protection from seed damage, although it was not entirely resistant to pink bollworm attacks. Conclusion Cotton plants were determined to produce both Cry1Ac and Cry2Ab proteins, albeit at relatively low levels, indicating that pink bollworm populations in Pakistan may not encounter effective toxin concentrations and/or may be exhibiting field-evolved resistance to these toxins. Immediate action is needed to manage this important pest of cotton.
Hanif et al. (Wed,) studied this question.