Bt Research 2024, Vol.15, No.1, 30-41 http://microbescipublisher.com/index.php/bt 38 resistance management, crop yields, and the costs associated with implementing integrated pest management (IPM) strategies. Bt crops have been shown to provide economic benefits by reducing the need for chemical pesticides and increasing crop yields, which can lead to higher profits for farmers (Gassmann and Reisig, 2022)). However, the evolution of pest resistance to Bt crops poses a significant challenge to their economic sustainability. As pests develop resistance, the effectiveness of Bt crops diminishes, potentially leading to increased crop damage and reduced yields. This necessitates the adoption of additional pest management strategies, such as the use of refuges of non-Bt host plants and the development of pyramided Bt crops that produce multiple toxins to delay resistance (Carrière et al., 2015; Ni et al., 2017). The economic viability of Bt crops also depends on their ability to maintain high yields under changing environmental conditions. For example, studies have shown that inoculation with arbuscular mycorrhizal fungi (AMF) can enhance the yield and insect resistance of Bt maize, particularly under elevated CO2 conditions, which are expected due to climate change (Wang et al., 2021). This suggests that integrating Bt crops with other sustainable agricultural practices can help ensure their long-term economic viability. 8.3 Case studies on sustainability Several case studies highlight the sustainability of Bt transgenic crops in different agricultural systems. In the United States, the use of Bt corn and cotton has led to regional suppression of pest populations and even pest eradication in some areas, resulting in reduced use of conventional insecticides and increased profits for farmers (Gassmann and Reisig, 2022). These positive outcomes demonstrate the potential for Bt crops to contribute to sustainable pest management and economic gains. In contrast, other case studies have documented instances where pests evolved resistance to multiple Bt traits, leading to increased crop damage and the need for additional pest control measures (Gassmann and Reisig, 2022). These cases underscore the importance of implementing effective resistance management strategies to sustain the benefits of Bt crops.Another case study from China demonstrated the effectiveness of pyramided cotton combining Bt toxins and RNA interference (RNAi) in delaying pest resistance and maintaining high crop yields (Ni et al., 2017). This approach highlights the potential for combining multiple pest control technologies to enhance the sustainability of Bt crops. 9 Concluding Remarks The long-term sustainability of Bt transgenic crops in agricultural systems has been extensively researched. Studies indicate that while Bt crops have significantly improved pest management and reduced reliance on chemical insecticides, the evolution of pest resistance poses a substantial threat to their efficacy. Research has documented an increase in pest resistance to Bt proteins over time, with practical resistance observed in several pest species across multiple countries. However, certain factors such as the recessive inheritance of resistance, abundant refuges of non-Bt host plants, and the use of pyramided Bt crops have been shown to delay resistance development. The incorporation of Bt residues in soil has been found to influence soil enzymatic activities, which could have implications for soil health and crop sustainability. The sustainability of Bt transgenic crops cannot rely solely on genetic modifications. Integrated pest management (IPM) strategies that combine Bt crops with other control methods are crucial. For instance, planting refuges of non-Bt crops alongside Bt crops has proven effective in delaying resistance. Moreover, the development of next-generation transgenic crops that combine Bt toxins with RNA interference (RNAi) technology shows promise in countering resistance. The use of arbuscular mycorrhizal fungi (AMF) to enhance the yield and resistance of Bt crops under elevated CO2 conditions is another innovative approach that could contribute to the long-term sustainability of these crops. These integrated approaches help manage resistance and maintain ecological balance and soil health.
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