Tree Genetics and Molecular Breeding 2024, Vol.14, No.6, 277-285 http://genbreedpublisher.com/index.php/tgmb 278 this section has been challenging due to reliance on macromorphological features, which can be variable. However, recent studies have utilized foliar sclereids, which are stable anatomical features, to address taxonomic issues. These sclereids exhibit a wide diversity and can be categorized into 12 types, providing a reliable basis for classification and identification of both wild and cultivated tea species (Zhang et al., 2009). 2.2 Geographic distribution and ecological niches Wild tea species are predominantly found in subtropical regions, with significant populations in China, particularly in Yunnan and Guizhou provinces. These regions provide diverse ecological niches, ranging from lowland subtropical forests to high-altitude mountainous areas. The distribution of wild tea is influenced by various environmental factors, including temperature, precipitation, and soil pH. For instance, Camellia taliensis, a wild tea species, is distributed from the west and southwest of Yunnan province to northern Myanmar, thriving in diverse habitats that contribute to its genetic diversity (Rao et al., 2018). The subtropical forests of China, rich in plant species, serve as crucial habitats for these wild tea species, supporting their conservation and utilization. 2.3 Genetic diversity in wild tea compared to cultivated varieties Wild tea species exhibit significant genetic diversity, which is crucial for breeding programs aimed at improving cultivated varieties. Studies using molecular markers such as EST-SSR and SNPs have revealed high levels of genetic diversity in wild tea populations. For example, Camellia taliensis populations in Qianjiazhai show high genetic diversity at the species level, with substantial gene flow among populations at different altitudes (Rao et al., 2018; Wang et al., 2023). In contrast, cultivated tea varieties, while also diverse, often show less genetic variation compared to their wild counterparts. This is evident in the genetic analysis of Camellia sinensis populations, where cultivated types exhibit a higher level of genetic diversity than pure wild types, but less than ancient landraces and admixed wild types (Niu et al., 2019). The genetic diversity in wild tea species provides a valuable resource for breeding programs, offering traits that can enhance disease resistance, stress tolerance, and other desirable characteristics in cultivated tea plants (Huang, 2024). 3 Genetic Traits in Wild Tea Species 3.1 Disease and pest resistance Wild tea species possess significant genetic traits that contribute to disease and pest resistance, making them valuable resources for breeding programs. For instance, certain genotypes of Camellia sinensis, such as Cd19 and Cd289, have demonstrated strong resistance to the tea green leafhopper, Empoasca onukii, under field conditions, which is a major pest in East Asia (Yorozuya et al., 2021). The genetic diversity found in wild tea species, such as those from the Guizhou plateau, also provides a rich pool of alleles that can be harnessed to develop resistant cultivars (Niu et al., 2019). These genetic resources are crucial for enhancing the resilience of tea plants against biotic stresses. 3.2 Abiotic stress tolerance Wild tea species are known for their ability to tolerate a range of abiotic stresses, including drought, salinity, and temperature extremes. Camellia taliensis, a wild relative of the cultivated tea tree, exhibits a remarkable expansion of late embryogenesis abundant (LEA) genes, which are associated with stronger stress resistance compared to cultivated varieties (Zhang et al., 2015). This genetic trait is particularly valuable for breeding programs aimed at developing tea plants that can withstand the challenges posed by climate change and other environmental stresses (Singh and Abhilash, 2018). 3.3 Quality-related traits The genetic diversity in wild tea species also extends to quality-related traits such as flavor, aroma, and phytochemical content. Genome-wide association studies have identified candidate genes involved in flavonoid biosynthesis, such as CsANR, CsF3’5’H, and CsMYB5, which play a crucial role in the production of catechins, key bioactive compounds in tea (Zhang et al., 2020). Additionally, genes associated with terpene biosynthesis, which contribute to tea aroma, have been significantly amplified in the tea plant genome through recent tandem duplications (Figure 1) (Xia et al., 2020). These findings highlight the potential of wild tea species to enhance the quality attributes of cultivated tea.
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