Bioscience Evidence 2024, Vol.14, No.2, 56-68 http://bioscipublisher.com/index.php/be 63 7 Genetic Diversity and Breeding 7.1 Genetic variability in natural populations Rehmannia glutinosa, a valuable medicinal plant, exhibits significant genetic diversity across its natural populations. Studies have utilized various molecular markers to assess this diversity. For instance, the use of SRAP molecular markers has revealed a medium-low level of genetic diversity among 21 species of R. glutinosa, with polymorphic loci percentages ranging from 8.77% to 54.39% and a Nei's genetic diversity index (H) of 0.374 1 (Shi et al., 2018). Additionally, expressed sequence tags (EST) derived microsatellite markers have been employed to confirm genetic relationships among 25 core germplasms, leading to the identification of four new cultivars (Li et al., 2018). These findings underscore the importance of genetic variability in the conservation and breeding of R. glutinosa. 7.2 Breeding strategies for enhanced medicinal traits 7.2.1 Traditional breeding techniques Traditional breeding techniques in R. glutinosa have primarily focused on the selection and cultivation of superior germplasms. Quantitative taxonomy and micromorphology analysis have been used to identify and classify different germplasms, aiding in the selection of high-yield and high-quality cultivars (Li et al., 2018). Additionally, the evaluation of genetic diversity and medicinal quality through molecular markers and HPLC analysis has provided theoretical guidance for screening excellent germplasms, such as those with higher contents of catalpol and verbascoside (Shi et al., 2018). These traditional methods have been instrumental in the development of new cultivars with enhanced medicinal traits. 7.2.2 Modern biotechnological approaches Modern biotechnological approaches have significantly advanced the breeding of R. glutinosa. The application of CRISPR/Cas9-mediated genome editing has enabled precise modifications in the R. glutinosagenome, such as the knockout of the phytoene desaturase (PDS) gene, resulting in the generation of albino plants and demonstrating high editing efficiency (Li et al., 2021). Furthermore, transcriptome sequencing has facilitated the identification of key genes and transcriptional regulators involved in the biosynthesis of important medicinal compounds like catalpol and acteoside, providing valuable insights for genetic improvement (Zhi et al., 2018). These biotechnological advancements hold great promise for the development of R. glutinosa cultivars with superior medicinal properties. In conclusion, the integration of traditional breeding techniques with modern biotechnological approaches offers a comprehensive strategy for enhancing the genetic diversity and medicinal potential of Rehmannia glutinosa. By leveraging the strengths of both methods, researchers can develop new cultivars that meet the growing demand for high-quality medicinal plants. 8 Biotechnological Applications 8.1 Genetic engineering for improved compound production Genetic engineering has been a pivotal tool in enhancing the production of valuable compounds in Rehmannia glutinosa. One notable example is the overexpression of the RgPAL family genes, which are involved in phenolic biosynthesis. This genetic modification has been shown to increase the production of phenolic compounds, although it also exacerbates replanting disease due to the release of allelopathic phenolics (Yang et al., 2020a). Similarly, the RgC3H gene, another key player in the phenolic acid/phenylpropanoid biosynthesis pathway, has been identified and manipulated to alter the release of allelopathic phenolic acids, further elucidating the molecular mechanisms underlying replanting disease (Yang et al., 2020b). Additionally, the CRISPR/Cas9 system has been successfully applied to R. glutinosa, demonstrating high editing efficiency and paving the way for future genetic modifications aimed at improving yield and quality (Li et al., 2021). 8.2 Tissue culture andin vitro propagation Tissue culture and in vitro propagation techniques have been optimized to address the challenges associated with traditional cultivation methods of R. glutinosa. These methods have been particularly effective in producing sterile
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