Pink bollworm, Pectinophora gossypiella(Saunders) (Lepidoptera: Gelechiidae) survival on transgenic cotton in India

Background: Insecticidal proteins from the Bacillus thuringiensis(Bt) marks the genetically modified cotton crop that was commercialized in India in March 2002 for the control of lepidopteron bollworms. Despite organized initial control, the pink bollworm (PBW), Pectinophora gossypiella(Saunders), adapted itself to cry toxins resulted in field control failures in 2016 and 2017.  The present study was designed to understand the survival and development of PBW populations differing in susceptibility to Cry toxins on Bt and non-Bt plants.  Results: For assessment of infestation, populations were collected from different cotton growing states. Per cent infestation of flowers and green bolls in the study areas were in the range of 3.09–29.26 and 36–91.20% for flowers and green bolls, respectively. Among different locations highest magnitude of resistance to Cry1Ac (371.8-fold) and Cry2Ab (4214.3-fold) was spotted in late season populations of Rajkot collected from bolls. Further, in order to confirm field level resistance of surviving larvae on high and low concentrations of Cry toxins, larvae were pooled and subjected to boll bioassays. Results revealed that, none of the larvae from susceptible populations survived on BGII bolls. Although, the same populations showed a survival of 38 and 32%, which led to 80% locule damage on non-Btcotton. Maximum survival (32%) and locule damage (70%) was observed for Maharashtra (F-H) Cry2Ab and Gujarat (B-H) Cry2Ab populations recorded 36% survival and 70% mortality, respectively, on BGII cotton and 58.33% survival and 60% locule damage on non-Btcotton, respectively. Populations derived from survivals on low concentrations produced the lowest survival and locule damage on Btcotton. Maximum number of mines on epicarp (2.4 mines/boll) was recorded by susceptible population on NBt cotton. Green bolls of Btand NBt cotton did not differ in the number of mines. Conclusion: It was concluded that none of the larvae from susceptible populations survived on BGII bolls. Although, the same populations showed a survival of 38 and 32%, which led to 80% locule damage on non-Btcotton