Journal of Tea Science Research, 2024, Vol.14, No.6, 304-312 http://hortherbpublisher.com/index.php/jtsr 305 This study provides a comprehensive synthesis of recent advances in uncovering the genetic and regulatory networks that control tea quality traits, including the identification of key functional genes, transcriptional and epigenetic regulators, and multi-omics-based network construction. It also highlights the practical potential of integrating systems biology approaches with molecular breeding technologies—such as marker-assisted selection, quantitative trait loci (QTL) mapping, and CRISPR-based genome editing—to accelerate the development of high-quality tea cultivars. A deeper understanding of these genetic networks not only enhances knowledge of trait evolution and diversification in Camellia sinensis, but also lays a solid foundation for precision breeding and the sustainable improvement of global tea quality. 2 Classification and Phenotypic Characteristics of Tea Quality Traits 2.1 Quality traits related to chemical composition The tea quality is established essentially by the chemical composition of tea, and this contains amino acids, catechins, flavonoids, phenolic acids, caffeine, and other volatile compounds. These metabolites create color, taste, and flavor in tea. Amino acids, for example, contribute to brightness and fresh-sweet tastes, while catechins contribute bitterness and astringency. Specific metabolites such as 4-hydroxybenzoyl glucose and feruloyl quinic acid control color luminance, whereas volatile compounds such as linalool and 1-octen-3-ol control flower and fruity scents. The processing and storage transformation and equilibrium of such a compound dictate the final quality of tea products (Fan et al., 2021; 2022; Guo et al., 2023). 2.2 Sensory quality attributes Sensory characteristics of tea are appearance, aroma, taste and mouthfeel. Traditionally, these are determined by expert sensory panels, but objective determination utilizing sophisticated analytical technology has more recently been used. Sensory quality is regarded as being closely related to chemical make-up: sweetness and umami are enhanced by high soluble sugar and amino acid levels and reduced by low caffeine and polyphenol levels responsible for bitterness and astringency. Aroma characteristics result from a sophisticated mixture of volatile compounds imparting floral, fruity, chestnut, or woody notes according to their composition. Instrumental methods such as near-infrared spectroscopy (NIRS) and metabolomics are nowadays utilized broadly for determining quickly and objectively sensory features. For example, in Enshi Yulu tea, sensory assessment not only includes visual inspection of different samples (Figure 1A) but also a qualitative inspection of fragrance, flavor, and the total mouthfeel scores (Figure 1B) with close agreement of sensory characteristics and quality factors (Wang et al., 2022; Guo et al., 2023; Lu et al., 2023). Figure 1 Enshi Yulu tea samples and sensory evaluation (Adopted from Guo et al., 2023) Image caption: A: Appearance of three Enshi Yulu tea samples; B: Sensory traits and score (Adopted from Guo et al., 2023)
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