Desmopressin (DDAVP): indications and practicalities.

The cotton bollworm, Helicoverpa armigera, is a highly destructive and polyphagous pest with major economic impact on cotton worldwide. In present study, ten field populations of H. armigera were collected from seven districts of Maharashtra and three districts of Gujarat representing Central India. These populations were evaluated against Cry toxins using diet incorporation bioassays. For Cry1Ac, most populations showed high resistance with resistance ratios exceeding 100-fold, Parbhani recorded highest LC₅₀ value of 2.90 ppm followed by Amreli, Ahmedabad and Washim. These four populations recorded resistance ratio above 200-fold. Nagpur (0.90 ppm) population showed low to moderate resistance and was least resistant field population recorded in present study. For Cry2Ab, most populations showed low to moderate resistance with Nanded (12.93 ppm) population recorded the highest LC₅₀ and Nagpur (3.67 ppm) recorded the lowest LC₅₀ indicating susceptibility with resistance ratio of 6.44-fold. The Cry1Ac resistance was inversely correlated with alkaline phosphatase (ALP) activity with correlation coefficient of 0.95. Nagpur population showed low to moderate resistance to Cry1Ac recorded highest ALP activity (643.55 U/L), while four most resistant populations Parbhani, Amreli, Ahmedabad and Washim had significantly lower ALP activity which was non-significant among these four resistant populations. Isozyme banding patterns ranged 55-80 kDa in Maharashtra and 55-100 kDa in Gujarat populations. For Cry2Ab, resistance showed moderate correlation with esterase activity that was non-significant. Molecular studies revealed ABCC2 domain mutations (NBD1, NBD2, ECL4) in resistant populations from Ahmedabad, Parbhani, and Buldhana, whereas comparatively lower resistant populations (Yavatmal, Anand) lacked mutations. These findings highlight possible association between ABCC2 mutations and Cry1Ac resistance with inverse correlation of ALP activity, indicating evolving biochemical and molecular adaptations that could threaten the long-term durability of Bt cotton in India.