Plant Gene and Traits 2024, Vol.15, No.4, 162-173 http://genbreedpublisher.com/index.php/pgt 168 strategies, including isolation distances and monitoring of transgenic rice variety and weedy rice populations, are essential to mitigate the risks. Additionally, the development of comprehensive biosafety guidelines that consider the specific ecological contexts and potential gene flow scenarios is crucial for the safe deployment of glufosinate-resistant rice varieties. The challenges in breeding glufosinate-tolerant rice are multifaceted, involving gene flow and contamination risks, environmental and ecological concerns, and regulatory and biosafety issues. Addressing these challenges requires a holistic approach that integrates scientific research, regulatory frameworks, and effective management practices to ensure the safe and sustainable use of transgenic rice technologies. 7 Advanced Techniques in Breeding Glufosinate-Tolerant Rice 7.1 Molecular breeding and marker-assisted selection Molecular breeding and marker-assisted selection (MAS) are pivotal in developing glufosinate-tolerant rice (Chen and Suh, 2015). These techniques involve the identification and utilization of specific genetic markers linked to desirable traits, such as herbicide tolerance. For instance, the development of herbicide-tolerant near-isogenic lines (NILs) in Basmati rice using marker-assisted backcross breeding (MABB) has been demonstrated successfully. In a study, a mutant allele of the acetohydroxy acid synthase (AHAS) gene, conferring tolerance to imidazolinone herbicides, was transferred into the genetic background of an elite Basmati variety, resulting in high-yielding, herbicide-tolerant lines (Grover et al., 2020). This approach can be adapted for glufosinate tolerance by identifying and utilizing markers linked to the bar or pat genes, which confer resistance to glufosinate. 7.2 CRISPR/Cas9 and gene editing technologies CRISPR/Cas9 and other gene editing technologies have revolutionized plant breeding by enabling precise modifications at specific genomic loci (Romero and Gatica-Arias, 2019; Nascimento et al., 2023). These technologies have been effectively applied to create herbicide-tolerant rice varieties. For example, CRISPR/Cas9-mediated gene editing was used to create a novel herbicide-tolerance allele in the OsALS gene, resulting in a high level of herbicide tolerance in rice (Wang et al., 2020). Additionally, the CRISPR/Cas9 system has been employed to develop DNA-free genome editing methods, which reduce the risk of off-target effects and regulatory concerns associated with genetically modified organisms (Mishra et al., 2018; Toda et al., 2019; Ansari et al., 2020). These advancements highlight the potential of CRISPR/Cas9 in developing glufosinate-tolerant rice by targeting specific genes involved in herbicide resistance. 7.3 Omics approaches (genomics, transcriptomics, proteomics) Omics approaches, including genomics, transcriptomics, and proteomics, provide comprehensive insights into the genetic and molecular mechanisms underlying herbicide tolerance. These techniques can identify key genes, regulatory networks, and metabolic pathways involved in glufosinate tolerance. For instance, advances in whole-genome sequencing and marker-assisted breeding strategies have significantly enhanced the ability to develop stress-tolerant rice varieties (Ganie et al., 2021). Furthermore, transcriptomic and proteomic analyses can elucidate the expression patterns and protein interactions associated with herbicide resistance, facilitating the identification of novel targets for breeding programs. Integrating omics data with traditional breeding and gene editing techniques can accelerate the development of glufosinate-tolerant rice. In summary, the combination of molecular breeding, CRISPR/Cas9 gene editing, and omics approaches offers a robust framework for developing glufosinate-tolerant rice. These advanced techniques enable precise genetic modifications, comprehensive understanding of resistance mechanisms, and efficient selection of desirable traits, ultimately contributing to sustainable weed management in rice cultivation. 8 Case Studies and Practical Applications 8.1 Successful breeding programs Several breeding programs have successfully developed glufosinate-tolerant rice varieties by integrating the bar gene, which confers resistance to the herbicide glufosinate. For instance, the commercial cultivars 'Gulfmont',
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