Journal of Tea Science Research, 2024, Vol.14, No.2, 79-91 http://hortherbpublisher.com/index.php/jtsr 86 epigenetic markers and their association with desirable traits can facilitate the development of improved tea cultivars through epibreeding (Jain et al., 2021). Furthermore, small RNA-mediated epigenetic pathways, such as microRNAs (miRNAs) and small interfering RNAs (siRNAs), orchestrate gene silencing and post-transcriptional regulation of target genes involved in secondary metabolism and defense responses (Lee and Carroll, 2018). The interplay between epigenetic modifications and environmental factors, such as temperature fluctuations and nutrient availability, underscores their role in phenotypic variability and adaptive plasticity across diverse tea cultivars and growing conditions. 6.3 Future directions in epigenetic research Future research in tea plant epigenetics should focus on several key areas. Comprehensive mapping of the tea epigenome at single-base resolution will provide a deeper understanding of the epigenetic landscape and its impact on gene regulation (Yuan, 2020; Zhao et al., 2020). Investigating the stability and heritability of epigenetic modifications across generations will be essential for harnessing epigenetic variation in breeding programs (Jain et al., 2021). Integrating epigenomic data with transcriptomic and metabolomic profiles will help elucidate the complex regulatory networks underlying important agronomic traits (Xia et al., 2020b). Furthermore, developing advanced tools and methodologies for precise epigenetic editing will open new avenues for crop improvement and functional genomic studies in tea plants (Yuan, 2020; Zhao et al., 2020; Jain et al., 2021). By advancing our understanding of epigenetic regulation in tea plants, we can unlock new potentials for enhancing tea quality, stress tolerance, and overall crop performance, ultimately benefiting both producers and consumers. 7 Case Study: Genome Studies in Select Tea Varieties 7.1 Selection of tea varieties for genomic analysis The selection of tea varieties for genomic analysis is crucial to understanding the genetic diversity and evolutionary history of tea plants. Various studies have focused on different tea cultivars to uncover the genetic basis of important traits such as quality, drought tolerance, and disease resistance. For instance, a haplotype-resolved genome assembly of the Oolong tea cultivar, Tieguanyin, was conducted to explore allele-specific expression and the evolutionary history of Camellia sinensis (Zhang et al., 2021a). The study shows that through the analysis of allele-specific expression, a potential mechanism for coping with mutation load has been revealed in tea trees during long-term asexual reproduction (Zhang et al., 2021a). By conducting a population genomic analysis of 190 Camellia samples, the population history of Camellia sinensis var. sinensis (CSS) and Camellia sinensis var. assamica (CSA) was uncovered, along with the independent evolutionary histories and parallel domestication of the two major cultivated varieties (Figure 3). Additionally, the study highlights the role of gene selection in the flavor characteristics of tea trees and the green revolution of the tea industry, providing crucial genetic resources and molecular insights for gene editing and trait improvement in tea trees. Another study focused on genomic selection in the breeding of black tea (Camellia sinensis). The research evaluated genome-enabled prediction models for tea quality and drought tolerance traits using machine learning techniques, including Extreme Learning Machine, Support Vector Machines, and Principal Component Analysis (Koech et al., 2019). The results showed that models combining QTLs (Quantitative Trait Loci), annotated proteins, and KEGG pathways had better predictive ability for catechins, astringency, brightness, briskness, and color of tea. The application of these models is expected to accelerate the tea breeding process, improve selection efficiency, and reduce costs and time (Koech et al., 2019). 7.2 Findings and implications The findings from these genomic studies have significant implications for tea breeding and cultivation. The haplotype-resolved genome assembly of Tieguanyin revealed independent evolutionary histories and parallel domestication in two widely cultivated varieties, var. sinensis and var. assamica. It also uncovered extensive intraand interspecific introgressions contributing to genetic diversity in modern cultivars (Zhang et al., 2021). These
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