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Principal component analysis (PCA) and multiple linear regression analysis (MLRA) were used to analyze and investigate the suitability of green tea for tea tree varieties in different tea cultivars. The fresh leaves of 63 tea cultivars planted in the same garden were processed into roasted green tea by the same method. The sensory and major physicochemical qualities (tea polyphenols, free amino acids, water extracts and chlorophyll) and the color (L*, a* and b*) of green tea were analyzed. To evaluate the suitability of the tested cultivars for green tea processing and its major influential factors, the data obtained were analyzed by PCA and MLRA. The results showed that the coefficient of variation (CV) of chlorophyll content in different cultivars was the highest (26.7%), followed by tea a* value (22.2%), sensory score for tea infusion color (17.1%) and sensory score for tea color (16.2%). A significant correlation was found between the polyphenol content of green tea and its color, tea infusion color and the color of infused tea leaves; between the chlorophyll content, |a*| and b* values of green tea and its color; between the chlorophyll content and |a*| value of green tea and the color of infused tea leaves; and between the |a*| and b* values of green tea and tea infusion color (P < 0.01). The PCA results showed that the contribution rate of the first five principal components (PCs) was 76.895%, and that of the first principal component was 31.918%, mainly pointing to the color quality. According to the evaluation model constructed based on the first five PCs, the top 10 cultivars were Zhongcha 108, Wuniuzao, Pingyangtezao, Mengshan 9, Soubeizhong, Fudingdabai, Jiukeng 16, Fudingdahao, Maolv, and Longjing 43. Using MLRA, the regression function between overall sensory score (Y) and |a*| value (x) was obtained as Y = 68.668 + 5.174x (R2 = 0.313) (P < 0.001). The top 10 varieties determined from this equation were highly consistent with the results of PCA, indicating that a* value is an important indicator for the evaluation of the suitability of tea cultivars for green tea processing.

To investigate the characteristics of quality formation of Simian tea, the non-volatile components, mineral elements and filamentary structure of fresh leaves from different positions of ‘Simian Tucha’ tea plants, endemic to Zigui, were analyzed using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), and scanning electron microscopy (SEM). The results showed that the non-volatile components were more abundant in the leaves with higher tenderness, with amino acids, alkaloids, catechins, and aroma glycosides being mainly concentrated in the first (L1) and second leaves (L2). Theanine, organic acids, and flavonoids were mainly concentrated in the third leaf (L3), while the content of non-volatile components in the older leaves was relatively lower. The accumulation of mineral elements greatly varied among tea leaves with different tenderness. The contents of nitrogen, phosphorus, potassium, zinc, and copper in L1 (32.41 mg/g, 4.53 mg/g, 15.65 mg/g, 45.45 μg/g, and 10.75 μg/g, respectively) and L2 (30.60 mg/g, 3.70 mg/g, 14.12 mg/g, 35.82 μg/g, 9.02 μg/g, respectively) were higher than those in older leaves. The contents of iron, manganese, and calcium were higher in mature leaves. Through SEM observation, it was found that the filamentary structure of Simian tea leaves consisted of two forms, triple-stranded coil and single-stranded coil, and was distributed in the internal thread or ringed vessels of the xylem in the vascular bundles in the midvein and lateral veins, and the number of filamentary structures was higher in the second, third and fourth leaves than that in buds and L1.

Matcha was prepared from 36 tea cultivars grown in the same tea garden according to the shading requirements for fresh leaves to be used for the production of matcha and its 11 quality indexes such as sensory quality, major physicochemical properties and chroma values were analyzed. In order to select tea cultivars suitable for the manufacturing of matcha, a comprehensive evaluation model of matcha quality was established by cluster analysis (CA), principal component analysis (PCA) and multiple linear regression analysis. The CA results showed that the 36 cultivars could be divided into three groups. Matcha from group I had the best quality with green color, fresh and mellow taste, and low phenol/ammonia ratio. Matcha from group II had high phenol/ammonia ratio and strong astringent taste. Matcha from Group III, consisting of etiolated and albino cultivars, had poor color and aroma quality. The PCA results showed that the cumulative contribution rate of the first five principal components was 88.152%. Comprehensive evaluation of matcha using the evaluation function constructed based on the first five principal components showed that the top 10 cultivars were Zhongcha 102, Taicha 12, Zhongcha 108, Fuding Dahao, Meizhan, Fuding Dabai, Fuyun 6, Zi Mudan, Maolv and Yingshuang. The model describing the relationship between sensory quality and physicochemical properties established by multiple linear regression analysis was as follows: y = 3.167|a*| + 46.850 (R2 = 0.710, P < 0.001). The scores of matcha cultivars evaluated by this model were highly consistent with the comprehensive evaluation results based on principal components, indicating that the a* value of dried tea could be used as a representative index to evaluate the quality of matcha. The results of this study can provide a reference for evaluating the suitability of tea cultivars for matcha manufacturing.

Surface-enhanced Raman scattering (SERS) provides an alternative rapid detection method for pesticide residues in food, but fenvalerate possesses poor affinity to the novel metal substrate, thus restricting its analysis. To break this bottleneck, a SERS-active platform with an Ag/rGO composite structure was engineered using a facile method for fenvalerate detection. Ag nanoparticles with a 60 nm diameter can grow evenly on the top and bottom of rGO layers under intense ultrasonic oscillation, and rGO in hybrid material acts as an ideal hotspot holder between the gaps of Ag nanoparticles, not only allowing the interaction area to be enhanced both electromagnetically and chemically but also enabling the capture and enrichment of fenvalerate pesticide molecules into the "hotspot" area to improve detection sensitivity. Ag/rGO composite substrate possesses superior SERS performance with an ultralow detectable concentration of 4-aminothiophenol (10−10 M) and good reproducibility, endowing the material with a better enhancement effect than pure Ag nanoparticles. When used as the SERS substrate for fenvalerate detection, Ag/rGO composite material showed excellent performance in both experiments and theoretical calculation, with the limit of detection (LOD) of fenvalerate being as low as 1.69 × 10−5 mg/kg and a detection model with an R2 of 99.2%, demonstrating its exciting potential as a SERS substrate for pesticides detection. [ABSTRACT FROM AUTHOR]

The tea plant [Camellia sinensis (L.) O. Kuntze] is a species with a high concentration of fluorine in its leaves, especially in the mature leaves. The physiological mechanisms for fluorine absorption and accumulation have been well studied, but the related molecular mechanisms are poorly understood in the tea plant. In this study, transcriptome analysis by RNA-Seq following exposure to 16 mg/L of fluorine for 0, 3, 6, and 24 h was performed to identify the candidate genes involved in the transmembrane transportation of fluorine. More than 1.23 billion high-quality reads were generated, and 259.84 million unigenes were assembled de novo, with 518 216 of them being annotated in the seven databases used. Meanwhile, a large number of transporters, transcription factors, and heat-shock proteins with differential expression in response to high levels of fluorine (P [less than or equal to] 0.05) were identified. Comparative transcriptome analysis showed that the uptake of fluorine is related to photosynthesis, plant hormone signal transduction, and glutathione metabolism. Further systematic analysis of nitrate and potassium transporter genes revealed that many of these genes regulate fluorine transportation in roots and leaves. Gene expression and fluorine content analysis in different cultivars revealed CsNRT1/PTR 3.1 and CsPT 8 as the key genes regulating the transmembrane transportation of fluorine in the tea plant. Key words: fluoride accumulation, CsNRT1/PTR, CsPT, transcriptome analysis, tea plant. Le theier [Camellia sinensis (L.) O. Kuntze] est une espece qui presente une concentration elevee de fluor dans les feuilles, en particulier les feuilles matures. Les mecanismes physiologiques d'absorption et d'accumulation de fluor ont ete bien etudies, mais les mecanismes moleculaires associes sont mal compris chez le theier. Dans cette etude, l'analyse du transcriptome par sequencage de l'ARN a la suite d'une exposition a 16 mg/L de fluor pendant 0, 3, 6 et 24 h a ete realisee pour reveler des genes candidats impliques dans le transport transmembranaire de fluor. Plus de 1,23 milliard de lectures de haute qualite ont ete generees et 259,84 millions d'unigenes ont ete assembles de novo, 518 216 d'entre eux etant annotes dans les sept bases de donnees utilisees. En parallele, un grand nombre de transporteurs, de facteurs de transcription et de proteines de choc thermique presentant une expression differentielle en reponse au fluor eleve (P [less than or equal to] 0,05) ont ete identifies. L'analyse comparative du transcriptome montrait que la captation de fluor est liee a la photosynthese, a la transduction de signaux hormonaux des plantes et au metabolisme du glutathion. Une analyse systematique plus poussee des genes de transporteurs de nitrate et de potassium a revele que plusieurs de ces genes regulent le transport de fluor dans les racines et les feuilles. L'analyse de l'expression genique et de la teneur en fluor dans les differents cultivars a revele que CsNRT1/PTR 3.1 et CsPT 8 sont les genes cles qui regulent le transport transmembranaire du fluor chez le theier. [Traduit par la Redaction] Mots-cles : accumulation de fluorure, CsNRT1/PTR, CsPT, analyse du transcriptome, theier., Introduction Fluorine (F) can be derived from phosphate fertilizer in an agricultural setting (Loganathan et al. 2001), or released into the environment from a numberof industrial sources (Mackowiak et al. [...]