1 Introduction

Aroma is a defining characteristic of tea (Camellia sinensis) quality, with a profound impact on sensory experience and consumer acceptance. Key volatile compounds—like linalool, geraniol, indole, and jasmine lactone—endow tea with unique floral, fruity, and sweet aromas, making high-quality tea sensory superior to ordinary tea (Zeng et al., 2019; Fang et al., 2022; Gao et al., 2023; Yu et al., 2023). The presence and concentration of these aroma compounds are directly related to the freshness, complexity, and overall pleasantness of tea, and are key factors affecting market value and consumer preference.

In recent years, the global tea market has seen a growing demand for teas with unique and attractive aromas, such as oolong tea, jasmine tea, and high-flavor black tea (Zeng et al., 2020; Wang et al., 2021; Fang et al., 2022; Chai et al., 2023). Consumer preferences for specific aromas—from floral and fruity to chestnut or light—have driven the development and commercialization of specialized tea varieties and processing technologies to meet diverse consumer expectations (Zeng et al., 2019; Liu et al., 2023; Yu et al., 2023). Therefore, the ability to cultivate and select for unique aroma characteristics has become a core focus for producers and researchers.

Different tea varieties have their own unique aroma spectrum, which is determined by their unique genetic background. For example, the oolong variety "Huangdan" is known for its high content of floral and fruity volatiles, while "Chungui" is known for its unique jasmine-like aroma (Wang et al., 2021; Gao et al., 2023; Fu et al., 2024; Li et al., 2024b). Green tea varieties such as "Bai-Sang Cha" and "Fuding-Dabai Cha" differ in the content of linalool, geraniol, and β-ionone, which are key contributors to their floral and grassy aromas (Gao et al., 2023; Liu et al., 2023). These variety-specific aroma characteristics are determined by differences in the biosynthesis and accumulation mechanisms of volatile compounds (Fang et al., 2022; Chai et al., 2023).

The accumulation of aroma compounds in tea is the result of a complex interaction between genetic and environmental factors, including pre-harvest stress, post-harvest processing, and epigenetic modifications (Zeng et al., 2019; Yang et al., 2021; Wu et al., 2023; Qiao et al., 2024). Genotype determines the potential for aroma synthesis, while environmental signals—such as mechanical damage, light, temperature, and biotic stress—regulate gene expression and metabolic pathways through mechanisms such as DNA methylation and chromatin remodeling (Zeng et al., 2020; Yue et al., 2025). This dynamic gene-environment interaction leads to the diversity and complexity of aroma lineages in different tea varieties and production areas.

This study explores the biosynthesis and regulatory mechanisms of key aroma substances in a variety of tea varieties, attempting to identify key genes, allelic variations, and their regulatory networks related to aroma diversity and quality. This study hopes to provide theoretical support for tea breeding projects, help cultivate new tea varieties with specific aromas, meet evolving consumer preferences and market trends, and promote the sustainable development of the tea industry.

2 Overview of Key Aroma Compounds in Tea Varieties

2.1 Major categories of tea aroma compounds

The aroma of tea is determined by a variety of volatile compounds, including terpenes (e.g., linalool, geraniol, β-ionone), alcohols (such as phenylethanol, 1-octen-3-ol), aldehydes (like phenylacetaldehyde, hexanal), ketones (such as 6-methyl-5-heptene-2-one) and esters (Chen et al., 2020; Feng et al., 2022; Xiao et al., 2022; Yu et al., 2023). These compounds give tea different floral, fruity, grassy, sweet and baked aromas, and are the main source of the aroma characteristics of various types of tea (Wang et al., 2020; Yu et al., 2023).

Secondary metabolites, like terpenoids and carotenoid degradation products, also play a key role in aroma formation. During the growth and processing of tea leaves, they generate important odor-active substances through biosynthesis and enzymatic reactions, thus shaping the unique sensory flavor of tea leaves (Feng et al., 2022; Zheng et al., 2022; Liang et al., 2024).

2.2 Distribution of aroma compounds in various tea cultivars

Different tea varieties have characteristic aroma spectra. For example, Longjing green tea is rich in geraniol, linalool and β-ionone, and has a distinct floral and sweet aroma (Wang et al., 2020). Varieties such as Fuding Dabaicha and Jinxuan also show unique volatile component compositions, among which the differences in the content of key compounds such as methyl salicylate, phenylacetaldehyde and β-geranyl constitute their unique sensory attributes (Xiao et al., 2022; Wang et al., 2025). White teas such as Baihaoyinzhen and Baimudan are mainly composed of alcohols and aldehydes, showing a fresh and grassy scent (Chen et al., 2020).

The aroma spectrum of tea is not only affected by genetic background, but also regulated by environmental factors such as geographical origin, processing methods and post-harvest treatment. For example, the baking process of oolong tea can enhance its roasted and cinnamon aroma, while tea that has not been deeply processed is more likely to retain the aroma of fresh leaves (Yang et al., 2021; Chen et al., 2024; Liang et al., 2024). This interaction between genotype and environment leads to large differences in the content and composition of aroma components between different varieties and production areas.

2.3 Detection and metabolomics analysis of aroma compounds

Gas chromatography-mass spectrometry (GC-MS), often used in conjunction with olfactory detection (GC-O) and solid phase microextraction (SPME), is currently a conventional method for identification and quantitative analysis of tea aroma components (Xiao et al., 2022; Yu et al., 2023; Wang et al., 2025). Non-targeted metabolomics methods can be used to conduct a comprehensive spectrum analysis of volatile components of different tea types and grades (Lin et al., 2023; Chen et al., 2024).

The identification of key aroma components is usually based on the test results of GC-MS and GC-O, and the calculation of odor activity values (OAVs) to evaluate the sensory contribution of each component in the overall aroma (Wang et al., 2020; Feng et al., 2022). Multivariate statistical analysis methods, such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), are helpful in distinguishing different aroma feature lineages and classifying tea varieties according to volatile characteristics (Chen et al., 2024; Wang et al., 2025).

3 Biosynthetic Pathways of Aroma Compounds in Tea

3.1 Biosynthesis of terpene-based aroma compounds

Terpene aroma components, such as linalool, geraniol and nerolidol, are important sources of floral and fruity aromas in tea. In the tea plant (Camellia sinensis), these compounds are synthesized mainly through two metabolic pathways: the methylerythrose phosphate (MEP) pathway in the chloroplasts and the mevalonate (MVA) pathway in the cytoplasm (Liu et al., 2018). The key enzymes in the MEP pathway include 1-deoxy-D-xylulose-5-phosphate synthase (DXS) and geranyl diphosphate synthase (GGPPS), while the key enzymes in the MVA pathway are hydroxymethylglutaryl-CoA synthase (HMGS) and hydroxymethylglutaryl-CoA reductase (HMGR). Terpene synthases (TPSs) play a core catalytic role in the final stage of synthesis, determining the production of specific monoterpenes and sesquiterpenes. These related genes are often induced to express during stress or processing such as withering or mechanical damage, promoting the accumulation of aroma substances (Wang et al., 2021; Qiao et al., 2022).

Differences in terpenoid biosynthesis ability are due to genetic variation among different tea varieties. For instance, in the high-flavor oolong variety "Huangdan", there is expansion and allelic variation in the TPS gene family, and these changes together shape its unique aroma characteristics (Wang et al., 2021; Gu et al., 2023). Quantitative trait loci (QTL) mapping and transcriptome analysis revealed candidate genes and regulatory modules associated with differential accumulation of terpenes in varieties such as "Huangdan", "Jinxuan", and "Jinguanyin" (Chen et al., 2023a; Gu et al., 2023; Gao et al., 2023; Wei et al., 2024). Transcription factors (e.g., MYB, bHLH, WRKY) and epigenetic modifications (such as DNA methylation and chromatin accessibility) also further regulate the expression of terpene synthesis genes, thereby forming variety-specific aroma expressions (Gao et al., 2023; Li et al., 2024b; Yue et al., 2025).

3.2 Phenylpropanoid and fatty acid-derived aroma compounds

Phenylpropanoid aroma compounds, such as phenylethanol and benzaldehyde, are derived from the shikimate pathway, whose key precursor is L-phenylalanine. Fatty acid-derived volatiles, such as hexanal and (E)-2-hexenal, are converted from linolenic acid and linoleic acid through the lipoxygenase (LOX) pathway (Zeng et al., 2019; Wu et al., 2023). Linalool belongs to the terpenoid class of compounds, but is also affected by the above two pathways under the cross-regulation of metabolic networks. The biosynthesis of these compounds is finely regulated by structural gene expression and is highly sensitive to environmental signals and processing stress (Gao et al., 2023; Zhou et al., 2024).

Because of differences in gene expression, allelic variation, and regulatory networks, the accumulation of phenylpropanoid and fatty acid-derived aroma components in different tea varieties varies significantly. For example, the expression of key biosynthetic genes (e.g., CsADH, CsLOX, and CsAOS) is regulated by transcription factors and stress signals (such as jasmonic acid JA and methyl jasmonate), which are often activated during postharvest processing (Wu et al., 2023; Li et al., 2024a; Zhou et al., 2024). In addition, epigenetic regulatory mechanisms such as DNA methylation and histone acetylation are also involved in the expression control of aroma-related genes, especially under adverse conditions (Yang et al., 2021; Li et al., 2024b).

3.3 Unique aroma compounds specific to tea plants

Tea plants have unique genetic and metabolic networks that contribute to the formation of their unique aroma components. For instance, UDP-glycosyltransferases (UGTs) participate in the glycosylation of aroma precursors, storing volatile compounds in the form of glycosides, and releasing free aroma components through hydrolysis during processing (Zhou et al., 2017). In tea plants, the expansion and functional differentiation of UGTs and other secondary metabolism-related gene families are jointly influenced by natural selection and artificial domestication, thus forming a diverse aroma spectrum (Wang et al., 2021).

Aroma markers of specific varieties are derived from their unique genetic background, allelic differences, and complex regulatory mechanisms. For example, the aroma of jasmine flowers in the "Chungui" variety is due to the synergistic effect of increased chromatin accessibility and DNA demethylation, which upregulates the expression of key aroma synthesis genes during processing (Li et al., 2024b). Similarly, QTL mapping and metabolome-wide association analysis have identified multiple specific genes and allelic variants associated with the accumulation of characteristic volatiles (Chen et al., 2023a; Gu et al., 2023).

4 Genetic Regulation of Aroma Biosynthesis in Tea

4.1 Structural genes involved in aroma biosynthesis

The biosynthesis of key aroma components in tea is mainly regulated by several structural gene families. Among them, terpene synthase (TPS) is the core enzyme for the synthesis of monoterpenes and sesquiterpenes, which gives tea its typical floral and fruity aroma. The expansion and diversification of the TPS gene family in high-aroma varieties such as "Huangdan" is the genetic basis for its rich volatile spectrum (Wang et al., 2021; Qiao et al., 2022; Gu et al., 2023). The lipoxygenase (LOX) gene family plays a key role in the production of fatty acid-derived aroma substances. The products, such as green leaf volatiles and jasmonic acid, not only have aroma characteristics, but also participate in plant defense mechanisms (Lin et al., 2024; Zhou et al., 2024). The phenylalanine ammonia lyase (PAL) gene is the starting enzyme in the phenylpropanoid metabolic pathway, catalyzing the production of phenylpropanoid aroma components such as phenylethanol and benzaldehyde (Gu et al., 2023; Gao et al., 2023).

Comparative genomics and transcriptome studies have shown that different tea varieties have large differences in the expression of aroma structural genes. In high-aroma varieties, such as "Huangdan" and "Jinguanyin", the expression of the TPS gene is upregulated, and there is allelic variation, resulting in an increase in the content of floral and fruity volatiles (Wang et al., 2021; Gu et al., 2023; Gao et al., 2023). Key genes in metabolic pathways, like MEP, MVA, LOX and shikimic acid often show allele-specific expression (ASE), which is one of the important reasons for the formation of variety-specific aroma spectra (Gu et al., 2023). Environmental factors and stress during processing (such as withering and mechanical damage) will further regulate the expression of these structural genes and promote the dynamic accumulation of aroma components (Zeng et al., 2019; Qiao et al., 2022; Lin et al., 2024).

4.2 Transcriptional regulation networks of aroma traits

Transcription factors (TFs), such as MYB, bHLH, WRKY, NAC and ERF, play a key role in regulating the expression of structural genes related to aroma synthesis (Wei et al., 2023; 2024; Yue et al., 2025). These transcription factors can recognize and bind to cis-acting elements in the promoters of structural genes (e.g., TPS, LOX and PAL), thereby regulating their transcriptional activity according to developmental signals or environmental stimuli. For example, MYB and bHLH transcription factors can form complexes to jointly activate or inhibit terpenoid synthesis, while WRKY and ERF factors are mostly involved in aroma regulation pathways under stress conditions (Huang et al., 2024; Li et al., 2024a).

Tea variety-specific aroma traits are often determined by genetic variation in transcription factor binding sites and allelic differences in regulatory genes. Variations in the promoter region of key TPS genes and differences in the expression of MYB, bHLH and WRKY transcription factors in different varieties are important reasons for the unique aroma spectra of oolong tea and jasmine-flavored tea (Wang et al., 2021; Li et al., 2024a; Yue et al., 2025). Multi-omics studies and QTL positioning analysis have screened out a series of candidate regulatory modules and key transcription factors that are involved in regulating the differential accumulation of aroma substances in different tea varieties (Chen et al., 2023a; Chai et al., 2023; Gao et al., 2023) (Figure 1).

4.3 Epigenetics and miRNA in aroma regulation

Epigenetic modifications, especially DNA methylation, play an important role in regulating the expression of aroma biosynthesis genes. Hypomethylation (demethylation) of the promoter region can increase chromatin accessibility, thereby activating the expression of key aroma genes during tea processing or stress conditions (Yang et al., 2021; Kong et al., 2023; Li et al., 2024b; Yue et al., 2025). For example, the “Chungui” variety develops a jasmine scent during processing, and the promoter regions of its aroma-related genes show enhanced chromatin accessibility and decreased methylation levels, leading to significant expression of key genes (Li et al., 2024b). The dynamic changes in DNA methylation are also involved in regulating the accumulation of key aroma substances such as indole during postharvest stress (Yang et al., 2021; Kong et al., 2023).

MicroRNAs (miRNAs) regulate aroma synthesis at the post-transcriptional level by targeting the mRNAs of TPS, LOX, and other structural genes (Zhao et al., 2018; Zhu et al., 2020). miRNAs and transcription factors form a regulatory network that synergistically controls the content of terpenoids and fatty acid-derived volatiles, allowing aroma components to be dynamically regulated under different developmental stages and environmental conditions. Specific miRNAs, have been shown to regulate the expression of transcription factors (like MYC2), thereby affecting the expression of downstream aroma synthesis genes and the activity of metabolic pathways.

5 Comparative Genomics and Aroma Traits in Tea Varieties

5.1 Genome-wide distribution of aroma-related genes

Comparative genomics has revealed extensive genetic diversity in tea, with large numbers of single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) identified across cultivars. For example, phased chromosome-scale assemblies of elite oolong cultivars like ‘Huangdan’ have uncovered numerous SNPs, InDels, and allelic imbalances related to aroma and stress tolerance, highlighting the importance of allelic variation in aroma trait diversity (Wang et al., 2021). Whole-genome resequencing of diverse accessions and wild/cultivated comparisons has further demonstrated that DNA polymorphisms are widespread, with tens of millions of SNPs and InDels detected, and that these variations are associated with differences in aroma profiles and quality between tea types (Xia et al., 2020; Zhang et al., 2021b; He et al., 2022).

Candidate gene regions for aroma biosynthesis have been pinpointed through comparative genomics and metabolome-wide association studies (mGWAS). Notably, expansions in terpene synthase (TPS) gene families and clusters have been linked to high-aroma characteristics in certain cultivars (Wang et al., 2021; Qiao et al., 2022). mGWAS in regional populations, such as Fujian tea cultivars, have identified hundreds of candidate genes associated with aroma metabolic pathways, providing a genetic basis for aroma variation and supporting the development of molecular markers for breeding (Gu et al., 2023).

5.2 Applications of QTL mapping and GWAS

Quantitative trait locus (QTL) mapping has made significant progress in identifying loci associated with aroma traits. For instance, in an F1 population derived from ‘Huangdan’ × ‘Jinxuan’, 42 QTLs for monoterpene contents and 12 for sesquiterpene contents were mapped, with several candidate genes identified in QTL clusters on specific chromosomes (Chen et al., 2023a). 

Genome-wide association studies (GWAS) and mGWAS have been instrumental in linking genetic variants to aroma-related metabolites and traits. Large-scale resequencing and GWAS have identified thousands of associations between SNPs and flavor traits, pinpointing candidate genes for aroma biosynthesis and supporting genotype-phenotype association studies for tea improvement (Xia et al., 2020; Liu et al., 2021; Kong et al., 2022; Gao et al., 2023). 

5.3 Multi-omics integration for understanding cultivar differences

Multi-omics approaches, integrating transcriptomic and metabolomic data, have provided new insights into the genetic regulation of aroma traits. For example, combined analyses in oolong tea have revealed that high-aroma varieties exhibit coordinated upregulation of aroma biosynthetic genes and accumulation of key volatiles (Zheng et al., 2019; Liu et al., 2021; Deng et al., 2023; Li et al., 2024a). Weighted gene co-expression network analysis (WGCNA) and other integrative methods have identified regulatory modules and candidate genes underlying volatile heterosis and cultivar-specific aroma profiles (Deng et al., 2023; Gao et al., 2023).

By integrating genomics, transcriptomics, and metabolomics, researchers have constructed regulatory networks that explain how genetic variation leads to cultivar-specific aroma profiles. These networks highlight the roles of structural gene expansions, regulatory variants, and epigenetic modifications in shaping the diversity of tea aroma traits (Wang et al., 2021; Kong et al., 2022; Li et al., 2024a; Yue et al., 2025). Pan-transcriptome and eQTL analyses have further revealed pleiotropic candidate genes and regulatory hubs that control specialized metabolite diversity across tea populations (Kong et al., 2022).

6 Case Studies: Genetic Basis of Aroma in Representative Tea Varieties

6.1 Mechanism of aroma formation during white tea withering

The floral and fruity aromas in white tea are mainly formed during the "withering" stage, and this process is regulated by specific enzyme activities, light, gene expression and processing methods (Wu et al., 2022; Deng et al., 2023). The three withering methods, indoor withering IWT, sun withering SWT, and trough withering WWT, have different effects on the aroma of white tea.

Deng et al. (2023) used Fuding Dahaocha (Camellia sinensis (L.) O. Kuntze) as the material, combined metabolomics and transcriptomics, and systematically revealed the formation mechanism of terpenoid and ester aroma substances during the withering process of white tea. The study showed that with the extension of withering time, the main volatile aroma components in tea leaves (especially terpenes and esters) accumulated significantly, and the aroma score and Owuor aroma index increased simultaneously (Figure 2). 

Key terpenes (such as linalool) and esters (such as 3-hexen-1-ol acetate) peaked at 12-30 hours, enhancing the perception of floral and fruity aromas. Gene expression analysis found that α-linolenic acid metabolism and jasmonic acid signaling pathways were activated, and related enzyme genes (like AOS and JAR) were upregulated, promoting aroma synthesis. In addition, the WGCNA co-expression network identified three modules closely related to aroma accumulation and locked in potential regulatory genes such as ACOT and GOLS2, which may promote the release of fatty acids through drought stress response mechanisms and provide a source for ester precursors (Deng et al., 2023; Liu et al., 2024). 

6.2 Oolong tea enhances aroma accumulation through JA pathway

The unique aroma of oolong tea is an important determinant of its quality and market value. Different tea varieties show great differences during processing (Kong et al., 2023; Li et al., 2024a). A study focused on two tea varieties, "Chungui (CG)" and "Fuyun No. 6 (F6)", which is not suitable for making oolong tea, and compared their aroma metabolism, transcriptome expression and jasmonic acid (JA) accumulation after withering and mechanical damage treatment (Li et al., 2024a). The study found that after treatment, the CG variety accumulated more typical oolong tea aroma substances, such as indole, (E)-β-farnesene, (E)-geraniol, jasmine lactone and linalool; the related synthase genes (e.g., TSB2, OCS, NES, AFS, LOX1) and the key genes of the upstream MVA, MEP, and ALA metabolic pathways were expressed at higher levels in CG than in F6 (Figure 3). This difference was confirmed to be closely related to the higher level of JA, especially methyljasmonic acid (MeJA) accumulation in CG after mechanical stress.

Further weighted gene co-expression network analysis showed that 34 transcription factors (such as MYC2, WRKY, bZIP, etc.) were involved in regulating the expression of JA response pathways and aroma synthesis genes. The active expression of m6A RNA demethylase CsALKBH10B in CG may stabilize key enzyme mRNAs and enhance aroma synthesis (Li et al., 2024a). The study revealed the dominant role of JA and its signal transduction in the formation of oolong tea aroma, providing a molecular basis for the breeding and regulation of future excellent aroma tea varieties.

6.3 Aroma gene variations in special tea varieties like Kudingcha

Specialty teas, like Kudingcha, are known for their unique or even strong flavors that are often different from traditional tea (Camellia sinensis) varieties. Multi-omics studies have shown that these special flavors are closely associated with the presence of specific alleles and variant sites in the aroma synthesis pathway (Chen et al., 2023a). For example, specific combinations of TPS, LOX, and phenylpropanoid pathway genes and their regulatory elements together form rare or highly enriched aroma components in these teas (Gao et al., 2023).

With the qRT-PCR, transgenic studies, and correlation analysis between gene expression and metabolite accumulation, researchers have functionally validated candidate regulatory genes in these special teas (Gu et al., 2023; Wei et al., 2024). In Kudingcha and other specialty teas, the expression of specific TPS and MYB genes is associated with the accumulation of unique terpenes and phenyl compounds. Metabolome-wide association studies (mGWAS) further confirmed the direct association between the occurrence and abundance of these aroma components and genetic variation (Wei et al., 2024).

7 Implications for Tea Breeding and Aroma Improvement

7.1 Molecular breeding strategies for improved aroma

Aroma is one of the core elements of tea quality. Modern breeding pays more and more attention to this indicator, not only pursuing high concentration, but also stability. The breeding goals include not only increasing the content of monoterpenes, sesquiterpenes, lactones and other ingredients, but also expanding the aroma types, such as floral, fruity, and milky aromas, and ensuring that these aromas can be stably expressed under different origins and processing methods (Zeng et al., 2020). At the same time, aroma traits are also expected to be compatible with agronomic traits such as stress resistance and high yield to meet market and planting needs (Wang et al., 2021; Gao et al., 2023; Fu et al., 2024).

Molecular marker-assisted selection (MAS) has become an important means to improve the aroma of tea trees. With the help of high-density genetic maps and QTL positioning, researchers have identified multiple key sites related to volatile terpenes (Parmar et al., 2022; Chen et al., 2023a; b; Gu et al., 2023). For example, in the F1 population, QTL regions related to monoterpene and sesquiterpene content were located, and candidate genes that can be used for breeding were screened (Chen et al., 2023a).

In addition, the developed SSR and SNP markers closely related to aroma genes and regulatory elements make it possible to screen for high-aroma materials at the seedling stage (Chen et al., 2023b; Parmar et al., 2022). MAS combined with multi-omics data (Li et al., 2022) further improved breeding efficiency and helped to cultivate high-quality and high-aroma new varieties.

7.2 Potential of genetic engineering in aroma improvement

Gene editing technology, especially CRISPR/Cas9, provides a direct and efficient tool for improving the aroma of tea. By precisely editing synthases such as TPS and LOX, or key transcription factors such as MYB and bHLH, the production of specific aroma substances can be greatly improved, and even new aromas can be created (Yue et al., 2025). For example, targeted editing of transcription factors that regulate linalool synthesis may produce varieties with more prominent floral or fruity aromas (Yue et al., 2025). The application of gene editing in tea trees is still in the exploratory stage, but there is already mature experience in other crops, and the relevant transformation system is also being continuously optimized, laying the foundation for subsequent applications in tea trees (Zhang et al., 2021).

Transgenic and synthetic biology methods also have potential. By introducing exogenous genes or overexpressing endogenous genes, such as β-glucosidase and methyltransferase, the efficiency of tea aroma release during processing can be improved (Deng et al., 2017; Wang et al., 2024). Furthermore, synthetic biology platforms can even construct entire aroma metabolism pathways to cultivate new varieties with more complex and customizable aromas. However, if these technologies are to be truly promoted, they still have to face practical problems such as regulatory review, ecological safety, and consumer acceptance (Zhang et al., 2021).

7.3 Green breeding strategies for stable and resource-efficient aroma traits

Green breeding emphasizes the use of tea tree genetic diversity and multi-omics data to select new varieties that are both fragrant and stable under the premise of protecting the ecology. By rationally combining the alleles of the parents, especially exploring hybrid advantages, it is expected to breed varieties with multiple and complex aromas (Fu et al., 2024). Multi-omics analysis can not only help identify the key modules that regulate aroma accumulation, but also provide a design blueprint for the aroma gene network to support targeted breeding (Zheng et al., 2019; Chen et al., 2023b; Gu et al., 2023).

In recent years, researchers have also begun to pay attention to the intersection between aroma and resistance. Some genes that regulate aroma, such as members of the TPS and UGT families, are actually involved in the stress response mechanism (Wang et al., 2021; 2024; Yue et al., 2025). This makes the breeding strategy no longer simply pursue aroma concentration, but emphasizes the dual improvement of "aroma" and "resistance". The goal is to allow excellent aroma to be stably expressed in complex environments, reduce external inputs such as pesticides, and promote the development of the tea industry in a more sustainable direction (Zeng et al., 2020; Yue et al., 2025).

8 Concluding Remarks

In recent years, the genome research of tea trees has made rapid progress, and the synthesis pathways of many key aroma substances have gradually become clear. Terpene synthases such as TPS are closely related to the production of volatile compounds such as monoterpenes and sesquiterpenes. Through QTL positioning, multi-omics joint analysis and other methods, researchers have found that the expansion of gene families, the variation of regulatory elements, and especially the changes in transcription factor binding sites are key factors affecting aroma diversity. At the same time, epigenetic mechanisms such as DNA methylation and chromatin accessibility also play an important role in the expression of aroma genes, especially in processing links such as withering and killing.

But, not all aroma formation mechanisms are exactly the same. Some pathways are very conservative between different varieties, but we can also see a lot of "personalized" regulation. In high-fragrance varieties such as "Huangdan" and "Chungui", there are not only specific allele variations, but also family expansions of some structural genes, which are the underlying reasons for their more prominent aroma. Some varieties also have differences in alternative splicing patterns and different stress response networks, which together constitute their unique aroma spectrum.

Despite a lot of progress, the genetic variation that can truly fully explain the aroma traits is still far from being in place. The role of SNPs, InDels and even structural variations needs to be explored in more varieties. To truly understand the logic of the formation of tea aroma, it is far from enough to rely on a single type of data. The genome, transcriptome, metabolome, and epigenetic group must all be combined. At the same time, the integration of synthetic biology and molecular breeding methods will also bring more precise regulation possibilities. Whether using MAS for assisted breeding or using tools such as CRISPR to address key regulatory points, the goal is the same-to cultivate new varieties with good aroma and stable performance. This will not only increase the added value of the product, but also drive the entire tea industry to develop more green and efficient.

Acknowledgments

The authors are particularly grateful to the two anonymous peer reviewers for their thorough evaluation of the manuscript. 

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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