Bt Research 2025, Vol.16, No.3, 103-109 http://microbescipublisher.com/index.php/bt 106 4 Environmental and Ecological Considerations 4.1 Impact of enhanced persistence Bt protein enters the environment through genetically modified crops and biopesticides, and over time, it will have two major impacts. On the one hand, Bt protein can combine with clay and humic acid in the soil, which will slow down its decomposition rate and keep it active in the environment for a longer time. This can help improve the pest control effect in the fields. On the other hand, this also means that non-target organisms and microorganisms in the soil may have long-term exposure to Bt proteins. Studies have found that Bt protein poses relatively little harm to most non-target organisms, and the negative effects detected in the field are generally much lower than those of chemical pesticides (Li et al., 2022). However, if it remains in the soil for a long time, it may affect the enzyme activity and microbial diversity of the soil. For instance, in the case of returning Bt crop residues to the field, the activities of some soil enzymes (such as dehydrogenase and urease) will increase, while the activity of neutral phosphatase will decrease (Li et al., 2019). In addition, the migration, adsorption and degradation processes of Bt protein in the environment are very complex. Some studies have shown that it can exist in the soil for several months or even longer. Therefore, long-term monitoring is still needed to have a clearer understanding of its possible impact on the ecosystem. 4.2 Regulatory and biosafety frameworks To address the potential risks that Bt proteins may pose in the environment, different countries have established relatively strict biosafety regulatory systems. Environmental safety assessment generally involves the detection of non-target organisms (NTOs), soil properties, microbial diversity and gene drift, etc. (Koch et al., 2015; Li et al., 2022). The commonly used Tiered testing method internationally: Acute toxicity tests are conducted with high doses in the laboratory first. If no obvious problems are found, then long-term evaluations in the field and larger ecosystems are carried out. In countries such as China, genetically modified crops and microorganisms must undergo systematic safety assessment before they can be applied in the field. Meanwhile, the regulatory framework also requires continuous monitoring of the behavior of Bt protein in the environment, degradation products, and its interaction with other pollutants (Li et al., 2022). With the continuous development of Bt technology, these regulatory systems are also gradually improving, with the aim of ensuring ecological security and sustainable utilization. 5 Case Study: Engineered Bt for Field Stability 5.1 Selection of case study Here, a classic case is selected to study the performance of Bt genetically modified broccoli in the field and its resistance to the armyworm. Through this case, the stability and management methods of BT-engineered crops in the actual field environment can be analyzed (Shelton et al., 2000). 5.2 Methodology of modification In this case, the researchers introduced the Bt toxin gene into the genome of broccoli. In this way, crops can continuously express Bt protein during their growth process, thereby possessing pest resistance. To ensure the stable existence of Bt protein throughout the entire growth cycle, they adopted molecular biological methods. Meanwhile, in combination with different field layouts, various resistance management methods were designed, such as "separate shelters" and "mixed shelters", to observe the effects of these methods on pest populations (Shelton et al., 2000). 5.3 Field trial outcomes The test results show that Bt genetically modified broccoli can significantly reduce the dependence on chemical pesticides and effectively control the number of pests. In terms of resistance management, in fields that use "isolated shelters", the number of larvae on non-BT crops is greater, which can preserve the genotypes of pests sensitive to Bt proteins and thereby slow down the emergence of resistance. In contrast, the effect of the "hybrid shelter" is not ideal and it is more likely to accumulate resistance genes. In addition, the experiment also found that if highly effective insecticides were sprayed in the shelter area, special care should be taken as this might disrupt the retention of sensitive genotypes.
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