关键词: 贵州, 茶, 大树茶, 遗传多样性, 主成分分析, 聚类分析

Abstract:

【Objective】 The aim of this study was to elucidate the morphological and biochemical characteristics of Guizhou Dashu tea germplasms in different regions, so as to provide the scientific basis for the conservation, development and utilization of Guizhou Dashu tea germplasms.【Method】In this study, 121 Dashu tea germplasms from seven counties in Guizhou were selected as materials to determine their morphological and biochemical traits. Multivariate statistical methods, including correlation analysis, principal component analysis (PCA), and cluster analysis were applied to comprehensively evaluate the genetic diversity of Guizhou Dashu tea germplasms. 【Result】The genetic diversity of biochemical traits was higher than morphological traits in Guizhou Dashu tea. The coefficient of variation (CV) for the 7 morphological traits ranged from 11.30% (length-width ratio) to 145.61% (ovary pubescence), with a mean CV of 41.12%. The index of genetic diversity (H') for them ranged from 0.47 (axillary pubescence) to 2.07 (length- width ratio), with an average value of 1.43. The CV of the 14 biochemical traits ranged from 23.15% (total catechins) to 99.54% (gallic acid), with an average value of 54.71%, and the H' ranged from 1.36 (epicatechin, EC) to 2.07 (total catechins), with a mean of 1.89. Most Guizhou Dashu tea germplasms were characterized by hairy axillary buds, glabrous ovaries, large or middle leaves, and long elliptical or elliptical leaf shape. The biochemical content of Guizhou Dashu tea from different regions were distributed uniform relatively, and 8 biochemical traits, including caffeine, theophylline, catechin (C), epigallocatechin-3-gallate (EGCG), total alkaloids, non-galloylated catechins, galloylated catechins and total catechins, showed a gentle and symmetrical normal distribution trend. Most of the morphological and biochemical traits of Guizhou Dashu tea were significant (P<0.05) or extremely significant (P<0.01) correlated with geographical location and climate factors. With the increase of altitude and latitude and the decrease of annual average temperature, the leaf of Guizhou Dashu tea germplasms were wider and rounder, and the content of purine alkaloids, such as caffeine, theobromine and theophylline, were higher. Based on orthogonal partial least squares discrimination analysis (OPLS-DA), 10 key traits, including total catechins, gallic acid, total alkaloids, gallated catechins, EC, caffeine, epigallocatechin gallate (ECG), EGCG, theobromine and axillary pubescence, with VIP >1 were screened out which could be used to distinguish Guizhou Dashu tea germplasms in different counties. Cluster analysis based on 10 biochemical components showed that the 121 Guizhou Dashu tea germplasms could be divided into 4 categories. There were 20 Guizhou Dashu tea germplasms in Group I, all from Huishui, had extremely significant higher content of EC and ECG than those in other three categories. 16 Guizhou Dashu tea germplasms in Group Ⅱ and the content of ECG was significant lower than that in other three categories. 9 Guizhou Dashu tea germplasms in Group Ⅲ, most of them came from Huishui, and the content of epicatechin-3-gallate (EGC) was significantly higher than that in other three categories. 76 Dashu tea germplasms in Group Ⅳ, mainly from Xishui, Tongzi, Daozhen and Wuchuan, and the content of caffeine, theobromine, theophylline, EGCG, C, and gallocatechin-3-gallate (GCG) were significant or extremely significant higher than those in other three categories. PCA was carried out with 14 biochemical traits, and a total of 3 principal components (PC1, PC2, and PC3) were extracted, with a cumulative contribution of 80.94%. The determinants of biochemical factors EGCG, total alkaloids and ester catechins in the PC1 were the key to evaluate the biochemical qualities of Guizhou Dashu tea.【Conclusion】Guizhou Dashu tea germplasms had abundant genetic diversity in morphological and biochemical traits. There were significant differences in morphological and biochemical characteristics between Dashu tea germplasms from Huishui, which located in southern Guizhou and those from other 6 counties, which located in northern Guizhou. Among them, GT-XS-08, GT-TZ-11, GT-DZ-06, GT-DZ-13, and GT-TZ-03 were Dashu tea germplasms with both superior biochemical quality and excellent biochemical content, which could be used as high potential breeding materials to select new tea varieties.

Key words: Guizhou, tea, Dashu tea, genetic diversity, principal component analysis, cluster analysis