Response of pink bollworm Pectinophora gossypiella (Saunders) to Cry1Ac and Cry2Ab toxin

Background During field surveillance in Gujarat, India, in 2009, scientists found that pink bollworm was surviving in the first generation of Bollgard cotton, which contains a single protein. This survival was observed in four districts of Gujarat. From 2012 to 2014, surveys revealed that pink bollworm larvae had higher survival rates on Bollgard II cotton in Amreli and Bhavnagar districts. In 2016, a pink bollworm outbreak in Maharashtra caused significant losses in cotton production, leading to damage, yield losses, and increased management costs in several regions. The objective of the present study was to determine the reaction of Pectinophora gossypiella to Cry1Ac and Cry2Ab toxins. Results Neonates of P. gossypiella collected from six distinct locations in Vidarbha were subjected to seven different concentrations of Cry1Ac. The highest LC 50 value was recorded in the population collection of Yavatmal (1.362 μg/ml diet) but the lowest LC 50 value of 0.600 μg/ml diet in Buldana population. The highest MIC 50 value was recorded in the population collected from Yavatmal (0.743 μg/ml diet) and the lowest MIC 50 value of 0.413 μg/ml diet in the Buldana population (0.431 μg/ml diet). The highest IC 50 value was recorded in the population collected from Yavatmal (0.303 μg/ml diet) but the lowest IC 50 value of 0.127 μg/ml diet in the Buldana population. Neonates of P. gossypiella collected from six different locations in Vidarbha were exposed to seven different concentrations (9.0, 3.0, 1.0, 0.333, 0.111, 0.037 and 0.012 for Cry1Ac and 27.0, 9.0, 3.0, 1.0, 0.333, 0.111 and 0.037 μg/ml for Cry2Ab) which revealed that the Yavatmal population had the highest LC 50 value of 94.294 μg/ml diet and the lowest LC 50 value was recorded in the Amravati population (42.144 μg/ml diet). The highest MIC 50 value of 27.258 μg/ml diet was recorded in Buldana population, but the lowest MIC 50 value was recorded in the Amravati population (12.881 μg/ml diet). The highest IC 50 value of 3.209 μg/ml diet was observed in Yavatmal population, and the lowest one was recorded in the Amravati population (1.574 μg/ml diet). Conclusions According to the LC 50 values, all of the P. gossypiella populations in Vidarbha were extremely insensitive and had field-evolved resistance to the Bt proteins found in the transgenic cotton varieties of Bollgard II.