Tree Genetics and Molecular Breeding 2025, Vol.15, No.5, 211-219 http://genbreedpublisher.com/index.php/tgmb 214 4.2 Provenance trials and performance evaluation under stress conditions Through field tests and performance evaluations under different adverse conditions (such as saline-alkali, drought, flooding, etc.), Metasequoia glyptostroboides materials that are more adaptable to the environment can be screened out. Studies have found that the fine root structure of Metasequoia glyptostroboides has obvious plasticity. It can adapt to aquatic or terrestrial environments through the adjustment of anatomical structure, enhancing the adaptability to environmental pressure (Yang et al., 2019). Some functional traits, such as leaf dry matter content and specific leaf area, vary greatly under different terrains and disturbance conditions, which also reflects the stress adaptability of Metasequoia glyptostroboides (Chen et al., 2020). 4.3 Hybridization and clonal propagation for desired traits In terms of breeding methods, hybrid breeding and asexual reproduction (such as cuttings and tissue culture) are important means to obtain and expand excellent stress-resistant genotypes. At present, the tissue culture and micropropagation system of Metasequoia glyptostroboides has been established. By optimizing the ratio of culture medium and hormones, the formation of buds and roots can be efficiently induced, thereby achieving rapid propagation of superior individuals (Xiong et al., 2019; Chornobrov et al., 2020). Xiong et al. ’s research in 2024 also found that exogenous hormones and culture conditions can regulate the formation mechanism of adventite roots, which provides theoretical support for asexual reproduction and the improvement of stress-resistant traits. 5 Molecular and Genomic Breeding Advances 5.1 Development of molecular markers (SSR, SNP, AFLP) for trait mapping Metasequoia glyptostroboides is a critically endangered species. The conservation of its genetic diversity and the selection and breeding of superior traits rely on molecular marker technology. Wang et al. (2020) demonstrated that high-throughput sequencing has developed 28 polymorphic SSR loci, with an average of approximately 8 alleles at each locus, enhancing the ability to distinguish genotypes in wild individuals and providing a fundamental tool for germplasm resource management and trait mapping. Li et al. (2025a) analyzed the introduced population using these polymorphic SSR markers and found that Metasequoia glyptostroboides had a relatively high genetic diversity at the species level (He = 0.640), and moderate differentiation among populations (Fst=0.117), indicating that molecular markers have significant value in genetic resource conservation and targeted breeding. However, at present, there are still few studies on SNP and AFLP in Metasequoia glyptostroboides, and further development is needed in the future. 5.2 Transcriptomic and genomic studies on stress-responsive genes In recent years, transcriptomics has provided new ideas for revealing the molecular mechanism of Metasequoia glyptostroboides’ stress resistance traits. Transcriptome and hormone analyses of adventite formation indicated that some differentially expressed genes (DEGs) were associated with hormone signal transduction and phenylpropanoid biosynthesis pathways, and 13 transcription factor families were found to be involved in regulation. This indicates that the interaction between hormones and gene expression is crucial for Metasequoia glyptostroboides’ adaptation to adverse conditions and root development (Figure 2) (Xiong et al., 2024). Furthermore, the phenotypic study of root structure also found that Metasequoia glyptostroboides adapted to different aquatic and terrestrial environments through changes in fine root anatomical structure and chemical composition (such as the deposition of lignin and linolenic acid), suggesting that there is a large diversity and complex regulatory network of its stress-related genes (Yang et al., 2019). 5.3 Prospects of genomic selection and CRISPR/Cas-based editing in M. glyptostroboides At present, there are no direct application reports of Metasequoia glyptostroboides genome selection (GS) and CRISPR/Cas gene editing. However, the existing molecular markers and transcriptome data provide a scientific basis for these cutting-edge technologies. Analysis of highly polymorphic SSR markers and population genetic structure provided parameters and candidate genes for genome selection (Wang et al., 2020; Li et al., 2025a). The stress-related genes and regulatory networks discovered in transcriptome studies also provide potential targets for gene editing (Xiong et al., 2024). In the future, with the advancement of Metasequoia glyptostroboides genome sequencing and functional gene annotation, genome selection and CRISPR/Cas technologies are expected to accelerate the breeding of new stress-resistant varieties and promote their application in ecological restoration.
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