Field Crop 2024, Vol.7, No.5, 270-277 http://cropscipublisher.com/index.php/fc 271 inserting genes from Bt into the cotton genome, enabling the plant to produce these insecticidal proteins throughout its tissues (Tabashnik et al., 2023). This innovation has significantly reduced the need for chemical insecticides, leading to environmental and economic benefits(Naranjo, 2011; Guan et al., 2020). 2.2 Mechanisms through which Bt cotton controls pests The primary mechanism through which Bt cotton controls pests is by producing Cry proteins that are toxic to specific insect larvae when ingested. These proteins bind to receptors in the gut cells of the larvae, causing cell lysis and eventually leading to the death of the insect (Yang et al., 2022). This mode of action is highly specific, targeting only certain pests such as the pink bollworm (Pectinophora gossypiella) and the cotton bollworm (Helicoverpa armigera), while being safe for non-target organisms and humans (Gassmann and Reisig, 2022). The effectiveness of Bt cotton can be enhanced by planting refuges of non-Bt cotton to delay the evolution of resistance in pest populations (Arends et al., 2021). 2.3 Success stories of Bt cotton efficacy in various cotton-growing regions Bt cotton has demonstrated remarkable success in various cotton-growing regions around the world. In the southwestern United States, a combination of Bt cotton, non-Bt refuges, and sterile insect releases led to the eradication of the pink bollworm. In China, the use of hybrid seeds that mix Bt and non-Bt cotton has effectively managed resistance and maintained the efficacy of Bt cotton (Tabashnik and Carrière, 2019). Australia has also seen long-term success with a proactive resistance management plan that has kept resistance allele frequencies low in pest populations (Figure 1) (Tabashnik et al., 2010). These success stories highlight the importance of integrated pest management strategies and the adaptability of Bt cotton to different agricultural contexts (Knight et al., 2021). Figure 1 Global status of field-evolved pest resistance to Bt crops. Each symbol represents 1 of 73 cases indicating responses of one pest species in one country to one toxin in Bt corn, cotton, soy, and/or sugarcane (Adopted from Tabashnik et al., 2023) The global map provides a visual representation of pest resistance to Bt crops, indicating varied responses across different regions. Red circles show areas with practical resistance, while yellow triangles signal early warnings of potential resistance, and green squares mark regions where pests remain susceptible. The data highlight significant cases of resistance in North and South America, India, and China. Additionally, proactive resistance management strategies, such as those implemented in Australia, have proven effective in maintaining pest susceptibility. This map underscores the importance of ongoing monitoring and management to mitigate resistance development globally. 3 Resistance Development in Cotton Pests 3.1 Patterns and mechanisms of resistance in target pests The development of resistance in cotton pests, particularly the pink bollworm (Pectinophora gossypiella) and cotton bollworm (Helicoverpa armigera), has been a significant challenge in maintaining the efficacy of Bt cotton (Liu, 2024). The pink bollworm has shown varied resistance patterns across different regions. In India,
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