Journal of Tea Science

Elucidation of the Molecular Mechanisms Underlying the Formation of the High EGCG3′′Me Content in Tea Germplasms

LI Yuanyuan, YAO Mingzhe, JIN Jiqiang

Journal of Tea Science. 2025, 45(6): 909-919. doi:10.13305/j.cnki.jts.2025.06.005

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Methylated catechins exhibit significant physiological activities, such as anti-allergy effects, and demonstrate stronger stability and higher oral absorption rate than unmethylated catechins. However, tea germplasms rich in methylated catechins are relatively rare. This study measured the EGCG3′′Me content in 447 tea germplasms from different regions with extensive genetic backgrounds, and two unique tea germplasms with high EGCG3′′Me content, namely ‘Jinxiu 2-2’ (JX) and ‘Pinming Tea’ (PM), were found. The tea germplasms JX, PM, and ‘Hongfugui’ (BFK) with high EGCG3′′Me content, as well as ‘Shuchazao’ (SCZ) with EGCG3′′Me content below the detection limit, were used as research materials. Relative expression levels of flavonol and anthocyanin O-methyltransferase (CsFAOMT1) in JX, PM, and BFK were significantly higher than that in SCZ. Further analysis reveals that four types of CsFAOMT1 alleles were cloned from the four tea germplasms, and all of them contain CsFAOMT1.3. Enzyme activity analysis at the protein level reveals that the CsFAOMT1 protein activities in the three tea germplasms with high EGCG3′′Me content all exhibit high activity with minimal differences between them. These results indicate that JX and PM can enrich EGCG3′′Me due to their high expression levels of CsFAOMT1. This study identified tea germplasm with high EGCG3′′Me content and elucidated the molecular mechanisms underlying its unique traits, providing important materials and theoretical basis for breeding new tea cultivars with high methylated catechin content.

Cloning of the CsPDAT1 Gene from Camellia sinensis and Its Role in Drought Tolerance

SHEN Yingzi, LI Duojiao, HU Xingrong, JIANG Li, ZHENG Zhaisheng, LIU Huikang, YUAN Ming′an

Journal of Tea Science. 2025, 45(6): 920-930. doi:10.13305/j.cnki.jts.2025.06.002

Abstract ( 45 )

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During the growth and development of tea plants (Camellia sinensis), abiotic stresses such as drought and salinity frequently occur, causing significant adverse effects on tea yield and quality. This study focused on the tea phospholipid: diacylglycerol acyltransferase 1 (PDAT1) gene and systematically investigated its function in response to abiotic stresses through bioinformatics analysis, gene expression pattern detection, and transgenic functional verification. Bioinformatics analysis reveals that the protein encoded by the CsPDAT1 gene possesses a typical lysophospholipid acyltransferase (lysoPLA) domain. Real-time quantitative PCR (qRT-PCR) results demonstrats that the expression of the CsPDAT1 gene was significantly upregulated under drought and high-salt treatments, particularly during the early stages of drought stress. To further elucidate its function, researchers constructed an overexpression vector for the CsPDAT1 gene and transformed it into Arabidopsis thaliana. Finally three homozygous T3-generation transgenic lines were obtained. Phenotypic analysis reveals that under drought stress, Arabidopsis plants overexpressing the CsPDAT1 gene exhibited a significantly higher seed germination rate compared to that of wild-type plants, along with reduced malondialdehyde (MDA) content, increased proline content, and significantly enhanced antioxidant enzyme activity. This study confirmed that the CsPDAT1 gene in tea plants enhances plant tolerance to abiotic stress by regulating cell membrane lipid metabolism and the accumulation of osmoprotectants, providing a theoretical foundation and genetic resources for stress-resistant molecular breeding in tea plants.

Aroma Quality Characteristics and Key Aroma Components Analysis of Green and Black Tea from Four ‘Huangjincha’-Related Cultivars

JIAO Haizhen, LI Le, TIAN Shuanghong, TIAN Jianhua, HU Mengqin, LONG Daibin, LÜ Haipeng, LIN Zhi, PENG Yun

Journal of Tea Science. 2025, 45(6): 931-942. doi:10.13305/j.cnki.jts.2025.06.001

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‘Huangjincha’ is a tradtional and local tea germplasm resource in Xiangxi, with an excellent flavor quality, especially its obvious aroma characteristics, which is highly favored by consumers. This study selected four tea cultivars, namely ‘Baojing Huangjincha 1’, ‘Huangjincha 2’, ‘Huangjincha 8’, ‘Huangjincha 18’, to produce ‘Huangjincha’ green and black tea samples. Sensory evaluation, gas chromatography-mass spectrometry (GC-MS), and relative odor activity value (ROAV) were used to analyze their aroma components. The results show that ‘Huangjincha’ green tea is characterized by its fresh and elegant aroma and a refreshing, sweet aftertaste, while ‘Huangjincha’ black tea exhibits distinct sweet and floral notes. A total of 101 volatile aroma compounds were detected in ‘Huangjincha’ green tea. Among these, esters and alcohols accounted for 34.4% to 53.5% and 21.9% to 36.3%, respectively. A total of 140 volatile aroma compounds were detected in ‘Huangjincha’ black tea, with alcohols, esters, and aldehydes being the main volatile components, accounting for 38.6% to 60.0%, 11.0% to 26.9%, and 9.7% to 17.8%, respectively. The primary aroma-contributing compounds of both ‘Huangjincha’ green and black tea were further screened. A total of 20 compounds were identified as key contributors to the aroma of ‘Huangjincha’ green tea, including linalool, 3,5-octadien-2-one, cis-jasmone, β-ionone, lauric acid, β-cyclocitral, and 2-pentylfuran. For ‘Huangjincha’ black tea, 33 shared key aroma components compounds were identified, including linalool, benzaldehyde, 3,5-octadien-2-one, trans-β-ionone, (Z)-linalool oxide (furanoid) and 4-heptenal. This study had preliminarily revealed the similarities and differences in aroma quality characteristics and chemical composition in ‘Huangjincha’ green and black tea made by different cultivars, which could be used to improve the processing technology system of ‘Huangjincha’.

Comparative Analysis of Seed Biological Characteristics and Endophytic Bacterial Diversity among Different Individual Plants of Ancient Tea Plants (Camellia sinensis) in Tongzi, Guizhou

LU Li, SHI Yin, WANG Yanxia, HUANG Xiaozhen

Journal of Tea Science. 2025, 45(6): 943-956. doi:10.13305/j.cnki.jts.2025.06.011

Abstract ( 39 )

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The seeds of ancient tea plants represent valuable natural genetic resources and gene pools, playing a crucial role in enriching tea plant genetic resources and maintaining genetic diversity. To investigate their characteristics, this study utilized seeds from 8 ancient tea plants (designated TZ-1 to TZ-8) and a locally cultivated tea plant (TZ-9) in Tongzi County, Guizhou Province, China. We systematically compared their biological properties, including morphology, 100-grain weight, water absorption rate, bulk density, germination rate, and tea saponin content. Additionally, we analyzed the endophytic bacterial diversity using high-throughput sequencing. The results reveal significant variations in the biological properties among the ancient tea seeds. Specifically, TZ-3 exhibited the highest 100-grain weight (269.52 g), while TZ-1 had the smallest values in these traits. The cultivated variety TZ-9 has the highest relative water absorption rate (32%) and germination rate (85%). Among the ancient tea plants, TZ-6 had the highest germination rate (76%), and TZ-2 had the lowest (11.67%). The tea saponin content varied from 21.00% to 49.91% among the ancient tea plants, with TZ-3 and TZ-4 exceeding 40%. The analysis of endophytic bacteria detects a total of 1 141 OTUs, covering 26 bacterial phyla. Among them, the richness of the TZ-3 community was the highest (OTU=185), and TZ-2 was the lowest (OTU=46). PCoA/NMDS analysis shows that the community structures of TZ-2, TZ-3, and TZ-8 were significantly separated, and this separation was independent of the ecological type (ancient/cultivated plants). Correlation analysis revealed that the abundance of genera such as Planctomycetota and Firmicutes was positively correlated with seed diameter, 100-grain weight, and tea saponin content (P<0.05), while Desulfobacterota and Bacteroidota were negatively correlated with water absorption rate. This study initially elucidated the association between the biological characteristics of ancient tea seeds and their endophytic bacterial communities, offering a theoretical foundation for the conservation and innovative utilization of tea germplasm resources.

Effect of Geographical Translocation on the Chemical Composition and Metabolome of Green Tea from Camellia sinensis cv. Huangshanzhong

WANG Mengqi, SONG Dapeng, YIN Hongxu, ZHOU Chao, FANG Fengxiang, LI Jiyan, YU Jie, ZHANG Na, DING Shibo

Journal of Tea Science. 2025, 45(6): 957-970. doi:10.13305/j.cnki.jts.2025.06.006

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The growing environment significantly influences the accumulation of chemical compounds in tea plants. However, systematic studies on the changes in chemical composition after translocating the tea cultivar ‘Huangshanzhong’ to the high-latitude Shandong region remain scarce. This study investigated the green tea samples of Camellia sinensis cv. Huangshanzhong from two regions: the native origin (YCD, Huangshan, Anhui) and a transplanted region (SD, Rizhao, Shandong). Differences in the content levels of the chemical components were analyzed. Additionally, widely-targeted metabolomics techniques were employed to identify differential metabolites and elucidate core metabolic pathways. The results demonstrate that SD samples exhibited significantly higher levels of water-soluble carbohydrates, total ash, water-soluble ash, water extract content and total galloylated catechins than YCD. While the total polyphenols and caffeine showed no inter-regional difference. SD accumulated more asparagine, glutamate, and arginine, whereas YCD was richer in flavor-related amino acids, such as theanine, GABA, lysine. Metabolomics analysis identified 116 differential metabolites (73 upregulated, 43 downregulated), with flavonoids exhibiting the highest abundance and diversity among them. KEGG enrichment analysis further revealed that the purine metabolism, phenylalanine metabolism, and pyrimidine metabolism pathways were the most significantly enriched pathways, contributing most to the differences between the SD and YCD samples. This study provided a systematic comparison of chemical components in green tea from cv. ‘Huangshanzhong’ after high-latitude transplantation versus the original cultivation, offering scientific insights into tea cultivar adaptation and flavor quality optimization.

Analysis of Quality Characteristics and Flavor Compound Differences Among Jingshan Green Tea, Matcha and Black Tea

LU Jian, FU Zhouping, MA Guicen, WANG Dong, HU Kangying, ZHANG Jingjing, CHEN Liyan, ZHANG Yingbin, ZHOU Sujuan, HONG Yiwei, ZHANG Xiangchun, CHEN Hongping, HOU Zhiwei, YU Jizhong

Journal of Tea Science. 2025, 45(6): 971-986. doi:10.13305/j.cnki.jts.2025.06.004

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Processing techniques significantly alter the accumulation and composition of internal components in tea, forming different categories of tea products. Currently, there is limited research on the accumulation of compounds in different categories of Jingshan tea and their impact on taste quality characteristics. In this study, Jingshan green tea, matcha, and black tea were selected as the research object. The contents of physicochemical components such as water extracts, tea polyphenols, amino acids, and caffeine were detected, and the main compounds that constitute the taste and aroma skeleton of Jingshan tea were analyzed. The results show that the contents of compounds related to taste, such as water extracts, tea polyphenols, theanine, and glutamic acid, were significantly higher in green tea than in black tea. Meanwhile, black tea exhibited the highest accumulation of γ-aminobutyric acid. Jingshan green tea, matcha, and black tea were characterized by their “rich floral aroma and refreshing sweetness”, “fresh and thick”, and “sweet fruit aroma and lingering sweetness”, respectively. A total of 101 volatile compounds were identified in different categories of tea samples (31 in green tea, 30 in matcha, and 40 in black tea), among which cis-jasmone and 4,8-dimethyl-1,3,7-nonatriene are the key components contributing to the “elegant and floral” aroma quality of green tea. β-ionone, α-ionone, and β-cyclocitral are the essential components for the “fragrance” aroma of matcha. Geraniol and methyl salicylate are the crucial components for the “sweet aroma” of black tea. The research findings would be beneficial for expanding the study of Jingshan tea's flavor chemistry and provided a valuable reference for enhancing the high-quality processing of Jingshan tea.

Effect of Roasting Temperature on Flavor Quality and Key Compounds of Wuyi Rougui Tea: Based on the Correlation between FTIR and Biochemical Components

GAO Ruizhen, LIN Zhiqiang, XIANG Jiaxin, CHEN Yuan, YU Wenquan

Journal of Tea Science. 2025, 45(6): 987-1005. doi:10.13305/j.cnki.jts.20251103.003

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This study aimed to elucidate the underlying mechanism by which roasting temperatures influence the flavor quality of Wuyi Rougui tea. Specifically, it sought to characterize the dynamic responses of biochemical components, antioxidant activity, and spectral features under varying thermal processing conditions. Wuyi Rougui tea leaves were processed at three roasting temperatures: (light roast 110 ℃, medium roast 125 ℃, high roast 140 ℃). A comprehensive analytical framework was implemented, integrating sensory evaluation, chromaticity analysis, ultra-high-performance liquid chromatography (UHPLC)-based quantification, and in vitro antioxidant capacity assessment. Fourier transform infrared spectroscopy (FTIR) coupled with chemometric modeling was employed. Raw spectral data were preprocessed to establish an orthogonal partial least squares-discriminant analysis (OPLS-DA) model for identifying characteristic wave numbers. Subsequent correlation analysis and partial least squares regression (PLSR) modeling reveal the relationships between spectral signatures and quality attributes (sensory parameters, chromaticity indices, biochemical constituents, and antioxidant activity). This ultimately identified the key compounds governing roasting-derived flavor profiles. The roasting temperature significantly modulated non-volatile metabolites and antioxidant capacity. Medium-fire-treated samples exhibited optimal sensory quality with a mellow taste profile. Elevated roasting temperatures progressively reduced tea polyphenols (TP), free amino acids (FAA), total flavonoids (TF), soluble total sugars (STS), catechin content, and DPPH radical scavenging capacity. The FTIR-OPLS-DA modeling (R²X=0.964, R²Y=0.991, Q²=0.981) identified two discriminative wave numbers: 1 018 cm^-1 (C-O-C vibration in carbohydrates) and 1 739 cm^-1 (The C=O bond of the ester is broken), which strongly correlated with taste attributes (|r|>0.69). The PLSR analysis further identified soluble sugars, FAA, ferulic acid, and chlorogenic acid as critical determinants of roasting flavor (R2 p>0.85). This study is the first to elucidate the synergistic interplay of soluble sugars, FAA, epicatechin derivatives (EGCG/EGC/EC), and phenolic acids (ferulic acid/CGA) in shaping the characteristic roasting quality of Wuyi Rougui tea. The findings established a theoretical foundation for precise roasting in Wuyi rock tea production and proposed a novel spectroscopy-guided quality control strategy.

Screening of Mechanical Harvestable Traits of Tea Cultivars

CHEN Jiaming, GUO Yang, GU Dachuan, LI Jianlong, CHEN Yiyong, HUANG Yanfeng, TANG Jinchi, YANG Ziyin

Journal of Tea Science. 2025, 45(6): 1006-1020. doi:10.13305/j.cnki.jts.2025.06.003

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In recent years, tea production in China has faced challenges of labor shortages, driving urgent industrial demands for mechanized harvesting technologies. The prevalent issues of high leaf fragmentation and low harvest quality in current mechanical systems are closely related to tea plant phenotypic traits. This study investigated seven widely cultivated tea cultivars mainly being suitable for black/oolong tea production in Guangdong Province. Phenotypic data from 100 quadrat sample plots of seven tea cultivars was systematically collected. Multiple analytical approaches, combined with mechanical harvesting quality predictive models, were employed to identify critical determining traits. The correlation analysis demonstrates that leaf length, leaf length-to-width ratio, length of one bud with two leaves, and length of one bud with three leaves were positively correlated with mechanical harvesting quality, whereas the total bud density showed a negative correlation. Grey relational analysis reveals significant associations between the mechanical harvesting quality and the leaf length-to-width ratio, leaf width, length of one bud with one leaf, and length of one bud with two leaves. Random forest analysis identifies the leaf length-to-width ratio, third internode length, and fourth internode length as critical traits influencing the superior harvest rate, intact rate, and fragmentation rate in mechanical harvesting, respectively. Further validation combined four phenotypic trait groups (full trait set, correlation-significant traits, grey relational>0.9, random forest top 6) with four machine learning algorithms to predict three core mechanical harvesting traits. The results demonstrate the grey relational traits achieved the optimal prediction for superior harvest rate (R²=0.65, RMSE=0.04), and random forest-selected traits were suitable for intact rate prediction (R²=0.86, RMSE=0.02), and complete trait group shows the highest fragmentation rate accuracy (R²=0.92, RMSE=0.01). Integrated modeling analysis identifies the length of one bud with two leaves and third internode length as key mechanical harvestable traits influencing black and oolong tea production. These findings established theoretical foundations and provided critical parameters for breeding tea cultivars optimized for mechanical harvesting.

Mitochondrial Genome Characteristics and Phylogenetic Analysis of Eotetranychus kankitus on Pomelo and Tea Plants

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

Journal of Tea Science. 2025, 45(6): 1021-1035. doi:10.13305/j.cnki.jts.2025.06.008

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Eotetranychus kankitus is an agricultural pest mite that damages many crops. Conducting mitochondrial genome analysis can clarify its structural characteristics and the phylogenetic relationships among species in the family of Tetranychidae species. The mitochondrial genome sequences of E. kankitus on pomelo and tea plants were obtained by PCR amplification, sequencing, assembly and annotation. The phylogenetic tree of Tetranychidae was constructed based on 13 protein-coding genes and 2 rRNA gene sequences by maximum likelihood and Bayesian methods. The mitochondrial genomes of E. kankitus on pomelo and tea plants were both in size of 13 032 bp, with GenBank accession numbers OQ955767 and OQ955768, respectively. Both the two mitochondrial genomes included 13 protein coding genes, 2 rRNA genes, 22 tRNA genes and a 40 bp control region, with a consistent gene arrangement. The sequence similarity rate of the two mitochondrial genomes was high, and base composition values of the whole genome and each region were close. E. kankitus on both hosts clustered into one branch in the phylogenetic tree, and the genetic distance between them was 0.068 0, which was much smaller than that between E. kankitus and other mites in Tetranychidae. A close relationship was showed between E. kankitus and Panonychus species in both genetic distance and phylogenetic analysis. According to analyses of mitochondrial genomes, the differentiation degree of E. kankitus on pomelo and tea plants was low, and the risk of transference between the two hosts was high. It is recommended that tea gardens with E. kankitus and surrounding citrus crops should strengthen field monitoring work.

Study on the Pesticide Safety Control against Tea Leaf Beetle Basilepta melanopus

QIU Huan, TAN Rongrong, CHEN Xun, WANG Hongjuan, HUANG Danjuan, WU Peizhuo, ZHU Fen, JIAO Long, MAO Yingxin

Journal of Tea Science. 2025, 45(6): 1036-1046. doi:10.13305/j.cnki.jts.20251103.002

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The indoor efficacy of eight chemical pesticides and six biological pesticides against Basilepta melanopus adult was evaluated using the leaf-dipping method. Field control efficacy trials were conducted to screen the pesticides for controlling B. melanopus adult, and the residues of these pesticides in dry tea were measured seven days after application. The results show that in the indoor efficacy test, 72 h after I-cyhalothrin (effective component 16.5 mg·L^-1), bifenthrin (effective component 55.6 mg·L^-1), chlorfenapyr (effective component 143 mg·L^-1), thiacloprid (effective component 124 mg·L^-1), tolfenpyrad (effective component 165 mg·L^-1), pyriproxyfen-chlorfenapyr (effective component 165 mg·L^-1) and natural pyrethrum (effective component 52.8 mg·L^-1) had higher lethality to the adult of B. melanopus, with lethality rates of 100%, 100%, 100%, 100%, 100%, 95% and 80%, respectively. Next were pyriproxyfen (effective component 1 480 mg·L^-1) and azadirachtin (effective component 16.5 mg·L^-1), with the lethality rates of 50% and 28%. The lethality rates of buprofezin, Empedobacter brevis, tea saponin, cineole, Metarhizium anisopliae CQMa421 were not significantly different from the clear water control. The maximum control efficacies of I-cyhalothrin (effective component 16.88 g·hm^-2), bifenthrin (effective component 56.25 g·hm^-2), chlorfenapyr (effective component 201 g·hm^-2), and natural pyrethrum (effective component 36 g·hm^-2) against B. melanopus adult after field application for 1~7 d were up to 100%, 100%, 93.99% and 40.82%, respectively. After 7 days of pesticide application, the residues of bifenthrin and chlorfenapyr were both lower than the maximum residue limits (MRL) in national standard (GB 2763—2021) and EU standard for pesticides in tea. Whereas the residue of I-cyhalothrin was only lower than the MRL in GB 2763—2021. Although the field control efficacy of thiacloprid (effective component 126 g·hm^-2) could be 98.31%, the residue in dry tea produced 7 days after application exceeded the MRLs in both GB 2763—2021 and EU standards. In conclusion, bifenthrin, chlorfenapyr, I-cyhalothrin and natural pyrethrum can be selected as needed for the control of B. melanopus adult in tea plantations.

Isolation and Identification of Pathogens Causing Tea Gray Blight in Xishuangbanna Tea Area

ZHU Luojuan, JIANG Bingbing, MA Yuqing, BI Lingfang, HOU Guoxi, LI Rui, LIU Di, DUAN Siyan, ZHANG Jin, ZHU Shusheng, YANG Min, GUO Cunwu

Journal of Tea Science. 2025, 45(6): 1047-1054. doi:10.13305/j.cnki.jts.20251103.001

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Tea gray blight is one of the major foliar diseases in tea plantations, significantly affecting both yield and quality. In July 2023, tea leaves exhibiting resembling gray blight symptoms were observed during a filed surver in tea plantations in Mengla County, Xishuangbanna Dai Autonomous Prefecture, Yunnan Province. As the causal pathogen of these symptoms had not been previously reported in this region, this study aimed to identify the causal agent and its taxonomic classification. The pathogen was successfully isolated and identified using a combination of tissue isolation, pathogenicity testing via wound inoculation, morphological characterization, and molecular phylogenetic analysis based on ITS and TUB genes squences. The results confirmed that the strain FN3-2, isolated from symptomatic leaves, was pathogenic. Based on morphological traits and molecular evidence, the pathogen was finally identified as Neopestalotiopsis protearum. The finding provided a scientific basis for the accurate disease diagnosis and biocontrol agent screening, contributing to the sustainable development of tea production in the region.

Screening and Safety Evaluation of Pesticides for Ectropis grisescens

MENG Xiangfei, ZHAO Yingjie, CAI Xiaoming, BIAN Lei, LI Zhaoqun, XIU Chunli, FU Nanxia, WU Mengtao, YANG Mei, WANG Guochang, LUO Zongxiu

Journal of Tea Science. 2025, 45(6): 1055-1065. doi:10.13305/j.cnki.jts.2025.06.009

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The tea geometrid (Ectropis grisescens Warren) is the most destructive defoliator in tea gardens in China. In recent years, E. grisescens has developed medium to high level resistance against common pesticides. To address this challenge, six chemical pesticides and three biological pesticides were selected and comprehensively evaluated from four aspects: laboratory toxicity assays, field evaluation, safety assessment for natural enemies, and pesticide residue analysis in tea leaves. The results of laboratory toxicity assays indicate that matrine (LC₅₀: 3.54 mg·L^-1), spinetoram (LC₅₀: 4.12 mg·L^-1), and spinosad (LC₅₀: 9.68 mg·L^-1) exhibited potent contact toxicity against the 2^nd instar larvae. In the stomach toxicity tests, spinosad (LC₅₀: 0.01 mg·L^-1), matrin (LC₅₀: 0.10 mg·L^-1), spinetoram (LC₅₀: 0.31 mg·L^-1), methoxyfenozide (LC₅₀: 11.06 mg·L^-1), chlorfenapyr (LC₅₀: 38.80 mg·L^-1), and indoxacarb (LC₅₀: 49.87 mg·L^-1) exerted relatively optimal stomach toxic effects on the 2^nd instar larvae. The subsequent field efficacy trials reveal that spinetoram, chlorfenapyr, spinosad, and indoxacarb all showed remarkable control effects on E. grisescens larvae. Spinetoram achieved a control efficacy over 90% after 1 and 3 days of application, highlighting its rapid and remarkable properties. For the other three pesticides, their control efficacy surpassed 80% on the 7^th day, indicating ideal long-term effectiveness. The toxicity assessment of natural enemies indicates that the LC₅₀ values of spinetoram (LC₅₀: 5.39 mg·L^-1), and spinosad (LC₅₀: 39.75 mg·L^-1) for Arma chinensis were higher than those for the 2^nd instar larvae. This finding suggests that using spinetoram and spinosad to control E. grisescens in the field poses relatively low risks to natural enemies. Finally, the results of pesticide residue analysis shows that only indoxacarb remained at 0.30 mg·kg^-1 after 7 days of application, and no other pesticide treatments were detected, all of which met the maximum residue limit standards in China (GB 2763—2021). In conclusion, spinetoram and spinosad, characterized by their high efficiency and safety, were appropriate for rotational use to control the Ectropis grisescens.

Design and Experiment of Fresh Tea Leaf Agglomeration Dispersing Device Based on Cross Airflow

JIA Jiangming, SHEN Yifan, CHEN Jianneng, HUAN Xiaolong, WU Chuanyu

Journal of Tea Science. 2025, 45(6): 1066-1082. doi:10.13305/j.cnki.jts.2025.06.010

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Sorting fresh tea leaves can achieve high value tea production, but fresh tea leaves are prone to agglomeration and difficult to disperse, which affects the sorting results and efficiency. In this paper, disperse aggregates in fresh tea leaves by cross airflow. The fresh tea leaf agglomeration dispersing device based on cross airflow consists of a frame, opposite-facing photoelectric sensor, conveyer belt, slide rail, observation plate, movable hinge, air nozzle and other components. Based on CFD-DEM joint simulation, the influence of the air nozzle offset, air nozzle line spacing, and tilt angle of air nozzle on the dispersion degree was analyzed. Design-Expert 13 software was used to design a three-factor, three-level orthogonal test protocol, and the optimal parameter combination was obtained using response surface optimization. The experimental results show that when the air nozzle was arranged with the optimal combination of parameters, the rectangular area of dispersed fresh tea leaves obtained after dispersion was 0.343 m², and the percentage of fresh tea leaves area was 0.241, which were 90.6% and 50.6% higher than the tea fresh leaf material without dispersion, respectively. The relative errors between the experimental and predicted values was less than 5%. This device achieved effective dispersion of fresh tea leaf agglomerates, providing ideal material pretreatment conditions for subsequent accurate sorting.

Study on Longjing Tea Grade Identification and Appearance Evaluation Method Based on Image Features and Intelligent Algorithm

HUANG Danyi, ZHAO Zhumeng, FAN Dongmei, LIN Jie, LU Yating, WANG Xiaochang, LI Lamei

Journal of Tea Science. 2025, 45(6): 1083-1094. doi:10.13305/j.cnki.jts.2025.06.007

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Longjing tea appearance features are crucial for assessing tea quality. In order to intelligently evaluate the appearance characteristics of Longjing tea and quickly recognize the grades, a method combining image features and intelligent algorithms for appearance quality assessment was proposed. Images of the six grades of the standard Dafo Longjing tea were collected and their shape, color, and texture features were quantified and extracted to construct a database of tea appearance grade characteristics. The appearance features were fused and input into five machine learning models, namely, Decision Tree, Random Forest, K-Nearest Neighbor, Gaussian Bayesian, and Support Vector Machine, for grade recognition training. Three convolutional neural networks, VGG16, ResNet18 and DenseNet121 were compared to build a deep learning model for Longjing tea appearance evaluation. Then the model was optimized by optimizers and learning rate decay. The results show that the fusion of shape and texture data combined with Support Vector Machine was the optimal model for grade recognition, with an accuracy of 91.14% and an F₁ score of 91.20%. The ResNet18 network structure was chosen to establish the optimal model for appearance evaluation. After optimization by Adadelta optimizer and CosineAnnealingLR learning rate decay, the recognition accuracies of Longjing tea’s flatness, straightness, tenderness, and color all improved, reaching 99.21%, 99.51%, 99.56%, and 99.68%, respectively. This study provided a theoretical foundation for the digital evaluation of the appearance quality of tea.

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