Journal of Tea Science

Research Progress of Quantitative Evaluation Methods for Tea Grade

ZOU Dan, YIN Xiaoli, GU Huiwen, LONG Wanjun, FU Haiyan, SHE Yuanbin

Journal of Tea Science. 2023, 43(6): 733-746. doi:10.13305/j.cnki.jts.2023.06.011

Abstract ( 213 )

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Grade is an important indicator for discerning the quality of green tea and other types of tea, and it is directly related to their selling prices. However, there is often a phenomenon of falsely labeling tea grades in the market, which seriously undermines consumer rights. At present, tea grade is mainly assessed by sensory evaluation. Sensory evaluation, after long-term development, has formed relatively unified standard, but it still has a certain subjectivity. To evaluate the tea grade more accurately and objectively, researchers have developed a series of quantitative evaluation methods for tea grade. Given the significant practical importance of evaluating tea grade, this article provided a comprehensive review of the recent research status in the qualitative and quantitative evaluation of tea grades, including bionic sensing intelligent sensory detection technology, specific chemical components detection and metabolomics techniques. Major problems and challenges on tea grade evaluation were discussed, and future development trend was also prospected in this study. It has positive guiding significance for objective, scientific and standardized evaluation and quality control of tea quality.

QTL Mapping and Candidate Gene Analysis for Timing of Spring Bud Flush in Tea Plants (Camellia sinensis)

WANG Liubin, WU Liyun, WEI Kang, WANG Liyuan

Journal of Tea Science. 2023, 43(6): 747-756. doi:10.13305/j.cnki.jts.2023.06.012

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The timing of spring bud flush (TBF) is an important agronomic trait of tea plants, which has great effects on the flavor quality and economic benefits of tea. In this study, to discover key candidate genes regulating TBF, a F₁ population of ‘Longjing 43’× ‘Baihaozao’ comprising 327 offspring was used and a two years’ investigation of TBF were performed in the tea garden. Based on the high-density genetic map constructed from the F₁ population, QTL mapping for the sprouting index (SPI) of tea plants was performed using MapQTL 6.0 and GACD 1.2 software. The phenotypes of SPI in 2022 and 2023 show significant trait segregation and exhibit obvious quantitative trait characteristics in the progeny population. MapQTL 6.0 was identified as a primary QTL (qSPI-5-1), which explained 18.30% (2022) and 7.60% (2023) of phenotypic variations, respectively. GACD1.2 software identified two stable QTLs (qSPI-1, qSPI-5-2), which explained 2.75%-18.40% of phenotypic variations. While qSPI-5-2 and qSPI-5-1 were largely overlapped. The confidence intervals of the above QTLs were compared to the reference genome of tea plants, and 23 candidate genes related to the TBF were found by function annotation analysis. These results provided theoretical references for further investigation on the regulatory genes and molecular mechanisms of spring bud flushing in tea plants.

Analysis of Photosynthetic and Fluorescence Characteristics of Albino Tea Plants

LIU Dongna, GONG Xuejiao, LI Lanying, HUANG Fan, YAO Yu, XU Yaqiong, GAO Yuan, LUO Fan

Journal of Tea Science. 2023, 43(6): 757-768. doi:10.13305/j.cnki.jts.2023.06.002

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To facilitate the scientific assessment of germplasm evaluation and cultivation management of albino tea plants (Camellia sinensis L.), this study investigated the photosynthetic pigment contents, as well as the photosynthetic and chlorophyll fluorescence characteristics of three albino cultivars, with the normal tea cultivar ‘Fuding dabaicha’ (FD) as the control. The results show that (1) the total chlorophyll content of yellow tea leaves was 71.7%-86.8% lower than that of the control cultivar, and the total carotenoid content remained between 0.16 mg·g^-1 and 0.31 mg·g^-1. (2) The net photosynthetic rate (P_n), stomatal conductance (G_s), water use efficiency (WUE), the maximum net photosynthetic rate (P_{n max}), and light saturation point (LSP) of three albino tea cultivars were significantly decreased, and the optical compensation point (LCP) was significantly was than those of the control. (3) The photosynthetic processes of albino tea cultivars, such as absorption, transformation and consumption of light energy were significantly different from those of the control. Among them, the relative variable fluorescence at L and J points in the OJIP curve of albino tea cultivars ‘Jinfeng 2’ (JF2) and ‘Zhonghuang 1’ (ZH1) were significantly higher. Among the chlorophyll fluorescence kinetic parameters, M_O, DI_O/RC, φD_O and φR_O increased significantly, while F_V/F_O, ET_O/RC, φP_O, φE_O, ΨE_O and PI_abs decreased significantly. Our study found that the photosynthetic efficiency, potential and ecological adaptability of albino tea leaves were significantly decreased. The significant reduction of photosynthetic pigment, the significant decrease of PSⅡ light capture and photosynthetic electron transfer efficiency, and the significant increase of heat dissipation energy were the considerable reasons for inhibition of photosynthetic performance in albino tea plants.

Population Structure and Genetic Differences of Tea Germplasm Resources in Fujian

YANG Jun, ZHANG Lilan, ZHANG Wenjing, CHEN Linhai, ZHENG Guohua, LI Yijing, WANG Rangjian

Journal of Tea Science. 2023, 43(6): 769-783. doi:10.13305/j.cnki.jts.2023.06.006

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The population genetic structure, genetic diversity, genetic differentiation, gene flow, molecular variance of 208 tea germplasm resources in Fujian were studied by using 38 pairs of SSR fluorescent primers, and the leaf traits were also investigated. The results show that the Nei’s genetic diversity index and Shannon’s information index of 208 tea resources in Fujian were 0.674 and 1.444, respectively. The average values of leaf area and length-width ratio were 27.442 cm² and 2.516, respectively. The genetic variation of tea germplasm in Fujian were mainly originated from individual genetic variation. The test materials were divided into 8 groups by the structure software analysis. The material sources in groups a, b, f, and h were single, while the material sources in groups c, d, e, and g were complex. The genetic background of tea population in different regions was similar. There were a total of 40 tea cultivars from Fujian in groups a, b, and e. Group a was mainly cultivars suitable for processing green tea. Group b was mainly cultivars suitable for processing oolong tea. The representative cultivars within group e were suitable for processing green tea. There is a certain correlation between the group attributes of group a, group b, group e and the suitable tea cultivars. Group c included the resources from Nanjing county, Yunxiao county and Pinghe county, with relatively close geographical locations. The group attributes are related to geographical sources. The gene flow value between group g and group e was 6.321, indicating frequent gene exchange between groups. The clustering of group similarity coefficients shows that group d and group b were closely related. The genetic differentiation between group h and other groups was obvious, and the characters of leaf area and leaf serration number were significantly different (P<0.05). The genetic relationship between group f and other groups was relatively distant, and there were significant differences in the characteristics of leaf serration number and leaf vein logarithm (P<0.05), showing that both group h and group f had certain uniqueness and need further identification. These research results provided a certain reference for the identification, screening, and utilization of tea germplasm resources in Fujian.

The Investigation of the Ameliorate Effect and Mechanism of EGCG on Non-obese GK Rat with Diabetic Kidney Damage

PENG Liyuan, ZENG Hongzhe, WAN Liwei, WEN Shuai, LIU Changwei, AN Qin, BAO Sudu, HUANG Jian'an, LIU Zhonghua

Journal of Tea Science. 2023, 43(6): 784-794. doi:10.13305/j.cnki.jts.2023.06.003

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Epigallocatechin gallate (EGCG) is an antioxidant and anti-inflammatory natural active ingredient, and fewer studies have been conducted on the antioxidant and anti-inflammatory effects of EGCG in DKD and the regulatory mechanisms. This study investigated the effect and mechanism of EGCG on diabetic kidney damage in non-obese GK rats with idiopathic T2DM. Two different doses of EGCG (10 mg·kg^-1 and 120 mg·kg^-1) were administered to GK rats for 4 weeks. The body weight and daily food intake of rats were monitored during the experiment. At the end of the experiment, the serum and kidney tissues were collected to detect some kidney biochemical and pathological indicators and Nrf2-Keap1/MAPK signaling pathway related gene expression levels. The results show that EGCG could improve the kidney morphology and significantly increase the activities of antioxidant enzymes (such as SOD, CAT and GSH-Px), and inhibit the release of proinflammatory cytokines (MCP-1, IL-1β). In addition, EGCG could restrain oxidant stress by up-regulate the expression level of Nrf2 and inhibit inflammation by down-regulating the expression levels of JNK, NF-κB and P38 genes in kidney. The improvement effect of high dose was better than that of low dose in the experimental range. In conclusion, these results indicate that EGCG could ameliorate kidney injury caused by diabetes, and its mechanism might be related to anti-oxidative stress mediated by Nrf2-Keap1/MAPK signaling pathways.

Analysis of Genetic Diversity and Genetic Structure in Geographic Populations of Stephanitis chinensis from China Based on Mitochondrial DNA COI Sequence

CHEN Shichun, JIANG Hongyan, LIAO Shuran, CHEN Tingxu, WANG Xiaoqing

Journal of Tea Science. 2023, 43(6): 795-805. doi:10.13305/j.cnki.jts.2023.06.008

Abstract ( 102 )

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The tea lace bug, Stephanitis chinensis, is an important pest of the southwest tea region in China, which has spread and caused disasters in recent years. To analyze the ecological adaptation mechanism and disaster law of S. chinensis, COI sequences of 240 adults from 12 populations of this pest were sequenced. The genetic differentiation, gene flow level and molecular variance were analyzed by DnaSP 6.12.03, Arlequin 3.5.2.2 and MEGA 7.0.26, respectively. There were 75 mutation sites and 38 haplotypes in the COI sequences of 12 geographic populations, and only Hap13 was a shared haplotype. Haplotype diversity index (H_d) of the total population was 0.827 79, H_d values between geographical populations ranged from 0.00 to 0.85. Fixed coefficient (F_ST) and gene flow (N_m) value of total population were 0.864 26 and 0.039 87, respectively. The results indicate that there are a high degree of genetic differentiation and a small degree of gene exchange of the total population in China. Population pairs of 5 populations (CQCK, CQWX, HBES, HBSY and SXHZ) had low genetic differentiation and frequent gene exchange (F_ST<0.06, N_m>4.50), while other population pairs had high genetic differentiation and less gene exchange (F_ST>0.25, N_m<1.00). Molecular variance analysis (AMOVA) supports that the genetic differentiation was mainly among populations (86.43%). Tajima's D and Fu's F_s neutrality test support that population expansion events occurred in the CQBN, HBES populations and the whole population around the Daba Mountains. In this study, the risk of both invasion expansion and original population expansion of S. chinensis in China was analyzed and speculated. It suggests that the field monitoring of the tea lace bug should be strengthened in tea plantations.

Study on the Influence of Tea Green Leafhopper Infestation on the Tenderness of Fresh Tea Leaves and the Extraction Rate of Metabolites Related to Oolong Tea Quality

WU Shuhua, MAO Kaiquan, CHEN Jiaming, LI Jianlong, XUE Jinghua, ZENG Lanting, YANG Yuhua, GU Dachuan

Journal of Tea Science. 2023, 43(6): 806-822. doi:10.13305/j.cnki.jts.2023.06.005

Abstract ( 138 )

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Tea green leafhopper is a major insect widely distributed in tea gardens, which has a significant impact on the yield and quality of tea. However, the effects of tea green leafhopper infestation on the tenderness of fresh tea leaves and the extraction rate of metabolites related to oolong tea quality remain unclear. By means of shear force measurement, broken tea rate analysis, oolong tea brewing, metabolite analysis and correlation analysis, it was found that the infestation of tea green leafhoppers significantly increased the contents of cell wall materials lignin, cellulose and pectin, and decreased the tenderness of fresh tea leaves and broken tea rate. The extraction rates of tea polyphenols, free amino acids, soluble sugars, catechin monomers, amino acid monomers and theanine were affected. Moreover, except for epicatechin gallate (ECG), the extraction of these taste substances and the tenderness of fresh tea leaves were significantly correlated with the contents of cell wall materials. In this study, the extraction rule of taste quality metabolites after tea green leafhoppers infestation was explored, and the influence of tea green leafhopper infestation on quality traits was explored from three aspects: tea picking, processing and brewing.

Changes of Rhizospheric Pathogen Alternaria sp. and Its Antagonistic Bacteria Pseudomonas sp. of Continuous Cropping Tea Plants Mediated by Phenolic Acids

LI Yanchun, WANG Yixiang, YE Jing, LI Zhaowei

Journal of Tea Science. 2023, 43(6): 823-834. doi:10.13305/j.cnki.jts.2023.06.007

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Tea plant is an important economic crop in China. Long-term continuous cropping of tea plants has resulted in severe problems such as the imbalance of soil microbial community structure, soil disease exacerbation. Exploring the molecular mechanism underlying the formation of continuous cropping obstacles in Tieguanyin tea gardens is of great significance for seeking effective techniques for preventing and controlling the continuous cropping obstacle phenomenon. In this study, the pathogen and its antagonistic bacteria were isolated from the rhizosphere of Tieguanyin tea garden and identified by methods such as microbial isolation and purification, and plate confrontation. Quantitative analysis was conducted on the number of pathogen and its antagonistic bacteria in the rhizospheric soils of different continuous cropping years (0, 1, 10, and 20 years). Simultaneously, high-performance liquid chromatography (HPLC) technology was used to detect the changes of phenolic acid contents in the rhizospheric soils of different continuous cropping years, and the ratio of various phenolic acids in the soils was simulated to investigate the effects of phenolic acids on the rhizospheric pathogen and its antagonistic bacteria. The results show that one pathogenic fungus Alternaria sp. was isolated and identified from the infected roots of Tieguanyin under 20 years’ continuous cropping, and an antagonistic bacteria Pseudomonas sp. was identified from the rhizospheric soils. Fluorescence quantitative PCR analysis shows that the content of Alternaria sp. in 20 years’ continuous cropping soils was significantly higher than 1 year tea garden, while the content of Pseudomonas sp. was significantly lower. Five phenolic acids, including p-hydroxybenzoic acid, vanillic acid, syringic acid, vanillin, and ferulic acid, were detected in the rhizospheric soils, with an average ratio of 38∶229∶11∶11∶3. Phenolic acids did not accumulate in the soils, but showed a trend of first increasing and then decreasing with the increase of continuous cropping years. Simulation experiments found that mixed phenolic acids at low to medium concentrations (30-120 mmol·L^-1) could significantly promote the mycelial growth of Alternaria sp. while single phenolic acid such as p-hydroxybenzoic acid, vanillic acid, and syringic acid at low concentrations (30 mmol·L^-1 and 60 mmol·L^-1) also significantly accelerated the mycelial growth of Alternaria sp.. However, p-hydroxybenzoic acid had an inhibitory effect on the growth of Pseudomonas sp., and the inhibitory effect increased with the increase of p-hydroxybenzoic acid concentration. Mixed phenolic acid and other single phenolic acids had no significant effect on the growth of Pseudomonas sp.. Therefore, phenolic acids, the root exudates of Tieguanyin tea plants, have different ecological effects on the key microbial communities in the rhizospheric soils, and are important factors causing the imbalance of microbial community structure and the increase of severe diseases and other continuous cropping obstacles. The research results provided a theoretical basis for further revealing the mechanism of continuous cropping obstacles in Tieguanyin tea plants.

Quantitative Analysis of Tea Leaf Serration Morphological Characteristics Based on Image Analysis

TANG Min, ZHONG Qitian, XU Jin, XIAO Fuliang, LI Jie, ZHAI Xiuming, HOU Yujia, GU Yu

Journal of Tea Science. 2023, 43(6): 835-843. doi:10.13305/j.cnki.jts.2023.06.004

Abstract ( 105 )

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The size, shape, and arrangement of tea leaf serrations are important criteria for assessing and evaluating tea germplasm resources. However, for a long time, the determination of these criteria has mainly relied on the experience of technicians, resulting in subjective judgments and uncertainties. In this study, a custom convolutional operator based on the geometric morphological features of leaves was introduced, and the existing image recognition algorithms were optimized. A quantification method for tea leaf serrations based on leaf image analysis was proposed. Through experimental validation, the results show that this method can rapidly and accurately obtain basic parameters such as leaf area, perimeter, and number of serrations. It can also quantify descriptive indicators such as serration sharpness, serration depth, and serration density using custom operators. The coefficients of variation for the quantified results are all less than 1%, indicating strong repeatability and high stability. Compared to manual subjective identification, the measurement time of this method does not exceed 30 s, effectively enhancing the accuracy and efficiency of evaluating the morphological characteristics of tea leaf serrations. It provided a new approach and perspective for the quantitative evaluation of tea germplasm resources.

Research on the Prototype and Process Parameters of Oolong Tea Rocking Green Mechanism of Non-circular Gear Planetary Gear Train

LIU Limin

Journal of Tea Science. 2023, 43(6): 844-856. doi:10.13305/j.cnki.jts.20231025.001

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In response to the problems of uneven tea stirring quality and poor effect caused by insufficient friction between fresh leaves in the current oolong tea rocking green mechanism, this paper designed a set of oolong tea stirring mechanism based on a non-circular gear planetary gear train. The kinematics analysis model of the mechanism was established and its optimal mechanism parameters were obtained. The pitch curve and tooth profile parameters (m=2, α=20°, z=51) of the non-circular gear were designed and obtained using MATLAB software. The structure design and prototype development of the device were completed. On this basis, a 3-factor and 4-level orthogonal experiment was designed and carried out to evaluate the stirring effect of oolong tea. Multiple indicators were transformed into a single indicator to obtain a comprehensive score that can evaluate the shaking effect. The optimal process parameters were determined through orthogonal test analysis. Under the combination of these process parameters, the effective shaking rate of oolong tea fresh leaves was 87.52%, the water loss rate was 30.19%, and the comprehensive score was 97.02% of traditional manual shaking. The experimental results show that the oolong tea rocking green mechanism and the non-circular gear planetary gear train could meet the shaking needs of different degrees of tenderness and quantities of oolong tea, making the processed oolong tea more similar to manual stirring.

Determination of Glyphosate and Its Metabolites in Tea by Automatic Solid Phase Extraction Combined with UPLC-MS/MS

YI Huajuan, ZHU Jieling, ZHOU Ruizheng, ZHENG Yaolin, ZHANG Shuquan, YANG Le, SU Yonglun

Journal of Tea Science. 2023, 43(6): 857-869. doi:10.13305/j.cnki.jts.2023.06.010

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An analytical method for the determination of glyphosate and its metabolite aminomethylphosphonic acid in tea was established by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted and preliminarily purified using a water dichloromethane system and the sample matrix was further purified by mixed-mode cation exchanger column filled with polystyrene bonded benzenesulfonic acid in an automatic solid phase extractor. The optimal derivation conditions obtained by orthogonal test and variance analysis were 5% sodium borate buffer solution and 10 mg·mL^-1 FMOC-Cl derivatizing agent for derivatization at room temperature for 2 h. The derived sample solution was subjected to gradient elution separation on HSS T₃ column and 5 mmol·L^-1 ammonium acetate solution (containing 0.1% formic acid)-acetonitrile mobile phase system. The targets were analyzed by UPLC-MS/MS and quantified by internal standard method. The linearity of glyphosate and aminomethylphosphonic acid was good in the concentration range of 0.2-50 ng·mL^-1 and the correlation coefficient (R²) was greater than 0.999. The detection limit of the method was 2 μg·kg^-1, and the quantitation limit was 5 μg·kg^-1. The recoveries of 5, 50 and 250 μg·kg^-1 were in range of 94.2%-106.7% with relative standard deviations of 3.8%-4.9%, at low, medium and high spiked levels. The method is suitable for the determination of glyphosate and aminomethylphosphonic acid residues in daily large quantities of tea samples in the laboratory with the advantages of high efficiency, high accuracy, high throughput, low matrix interference and high degree of automation.

Does Digital Capital Influence Consumers to Increase Online Tea Purchases? An Empirical Analysis Based on 4 090 Consumer Samples

GAO Feng, XU Jianghong, CHEN Fuqiao

Journal of Tea Science. 2023, 43(6): 870-880. doi:10.13305/j.cnki.jts.2023.06.001

Abstract ( 137 )

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With the rapid development and widespread application of digital technology, consumer digital capital continues to accumulate, profoundly influencing their choice of shopping channels. Based on survey data from 4 090 tea consumers within the National Tea Industry Technical System, this study measured the consumer digital capital index and employed the ordinary least squares (OLS), instrumental variable (IV), and propensity score matching (PSM) methods to examine the impact of digital capital on consumers' online tea purchases. The research further explored the heterogeneity of this influence across consumers with different characteristics and delved into the moderating effect of digital technology security within this context. It was found that: (1) An increase in consumer digital capital led to higher expenditures on online tea purchases. (2) The impact of digital capital was more pronounced in young people, higher-income groups, and consumers who buy tea for personal consumption. (3) The decision security of digital technology played a positive moderating role in the relationship between digital capital and online tea purchases, particularly transaction security. However, the moderating effect of information security was not significant. In summary, the increase in consumer digital capital is the trend. Tea enterprises should seize the opportunities presented by digital transformation and actively establish online sales channels. The government should provide comprehensive support in terms of policies, funding, and technology for the digital transformation of tea enterprises. Simultaneously, there should be increased supervision of online sales markets to maintain quality and safety, creating a salubrious and well-ordered online tea trading market environment.

The Impact of Organic Certification on the Business Profit of Tea Enterprises: Counterfactual Estimation Based on Propensity Score Matching

YANG Xulin, PAN Changjian, JIANG Renhua

Journal of Tea Science. 2023, 43(6): 881-890. doi:10.13305/j.cnki.jts.2023.06.009

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This paper empirically examined the impact of organic certification on tea enterprises’ business profit using the propensity score matching method based on the data of 288 tea enterprises nationwide. The empirical evidence shows that organic certification has a positive effect on the business profit of tea enterprises, and this effect is heterogeneous in different regions and different tea plantation sizes. Compared with the central and western tea enterprises, the participation of eastern enterprises in organic certification has a significant effect on improving business profits. Compared with tea enterprises with a median or higher area of their own tea gardens, enterprises with smaller area of their own tea gardens have a greater benefit from participating in organic certification. Accordingly, governments can support tea enterprises to carry out organic certification in the framework of green development. Enterprises in the central and western regions can learn from the practical experience of the development of organic tea in eastern enterprises. Tea enterprises need to combine their own development positioning and market demand, consider whether to promote the quality and efficiency of enterprises through organic certification.

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