Evaluation of Cry1Ac and Cry2Ab Expression and Refugia Proportions in Bt Cotton (BG-II) Using ELISA

Abstract

The cultivation of genetically modified (GM) Bt cotton expressing Cry1Ac and Cry2Ab proteins has become an important strategy for effective insect pest management and enhanced crop productivity. The present study evaluated 40 commercially available Bt cotton (BG-II) hybrids for Cry protein expression and refugia proportions using enzyme-linked immunosorbent assay (ELISA). Qualitative ELISA demonstrated high sensitivity and specificity for detecting Cry1Ac and Cry2Ab proteins in cotton leaf tissues. The percentage of non-Bt plants (refugia) among hybrids ranged from 0.0 to 11.9%, indicating considerable variation in compliance with the recommended 5-10% refugia requirement. Several hybrids were below the prescribed refugia limit, while one hybrid exceeded the upper permissible limit. Seed cotton yield among hybrids varied from 1911 to 3813 kg/ha, with significant variability also observed for boll number, boll weight, lint yield, and phenological traits. Statistical analysis revealed substantial differences among hybrids for agronomic and quality traits, indicating the presence of considerable genetic variability. The findings demonstrate that ELISA is an efficient and reliable tool for routine monitoring of Bt protein expression and verification of refugia proportions in Bt cotton hybrids. This study supports regulatory compliance, quality assurance, and sustainable resistance-management strategies in transgenic cotton cultivation.