Preliminary Study On Species Diversity And Genetic Diversity Of The Main Wild Tea Tree Population In Sichuan

The field surveys were conducted to investigate the distribution of wild tea resources in Chongzhou,Dayi,Gulin and Leibo counties of Sichuan Province.Based on morphological characteristics,198 representative wild big tea plants were selected from loquat tea in Chongzhou,loquat tea in Dayi,loquat tea in Yingjing,kraft tea plants in Gulin,wild big tea tree in Xuyong and wild big tea tree in Leibo,respectively.Phenotypic characters and morphological diversity of various wild tea populations were systematically studied,and then SSR markers were used for genetic diversity analysis.On this basis,we systematically compared the morphological and genetic diversity of wild big tea plants in Sichuan,and further compared the morphological and genetic differences between Sichuan Province and Yunnan Province.Studies show that:(1)The distribution area and phenotypic characters of loquat tea in Chongzhou,loquat tea in Dayi,loquat tea in Yingjing,kraft tea plants in Gulin,wild big tea tree in Xuyong and wild big tea tree in Leibo were observed,the results showed that the main wild tea germplasm resources in Sichuan were mainly distributed in natural communities at 28°11’N～30°46’ N,103°24’E～105°33’"E and altitudes of 827 ～ 1291 m.Shrub is the main tree type of the loquat tea in Dayi,kraft tea plants in Gulin,the wild tea tree in Xuyong and Leibo,while Chongzhou loquat tea and Yingjing loquat tea are trees.The treetops are mostly half-open and sparsely branched.Most of the leaves are middle leaves,large leaves,and some leaflets,and leaf tip is acuminate.The middle flower type is predominant,the petals are mostly white,and the number of style dehiscences is 2～5,mostly 3,in which a few styles of Chongzhou loquat tea and Dayi loquat tea are 5.Based on the evolutionary path of the presence or absence,tree type,and leaf tip of ovary hairs,the above six species of wild big tea trees belong to Camellia gymnogyna Chang,C.sinensis var.sinensis and C.sinensis var.Assamica(Masters)Kitamura.Most of the loquat tea in Chongzhou is Camellia gymnogyna Chang,and the rest is C.sinensis var.Assamica(Masters)Kitamura;Dayi loquat tea,Yingjing loquat tea and Leibo wild big tea tree are mainly C.sinensis var.Assamica(Masters)Kitamura,and the rest are Camellia gymnogyna Chang.Gulin kraft tea plants and Xuyong wild big tea tree are C.sinensis var.sinensis,and the rest are Camellia gymnogyna Chang.However,the observed wild big tea trees in Yunnan are mainly arbor type,with mostly half-open posture,mostly medium oval leaf type,mostly acuminate leaf tips,large diameter of corolla,and the number of styles of cracks is 4 to 7 cracks,mostly 5 cracks.It belongs to C.tachangensis F.S.Zhang or C.taliensis(W.W.Smith)Melchior.(2)Statistical analysis of 30 phenotypic traits of 198 tested accessions showed that coefficient of variation of phenotypic traits of main wild tea germplasm resources in Sichuan is 26.06%,and average diversity index is0.8679.Coefficient of variation between regions is 23.80%～27.06%,and average diversity index is 0.6892～0.9988.Based on 30 traits of 198 tea resources,cluster analysis was performed using MEGA6.06,which were divided into two groups.The results showed that the main wild big tea plants in Sichuan tested underwent continuous and progressive changes in both botanical traits and characteristics.The leaf types evolved from lanceolate to oval,the leaf edge serrations evolved from shallow to medium,and the leaf tips evolved from acute to acuminate,and showed extremely rich diversity.The characters of tea flower of wild big tea in Sichuan were significantly different from those of the wild big tea plant in Lincang,Yunnan.Its corolla has a smaller diameter,fewer petals,and fewer stigmas.(3)SSR amplification using 33 primer pairs showed that the gene diversity(Fis)of the tested accessions within the same type of wild big tea plants in Sichuan ranged from-0.2481 to 0.4936,with a mean value of 0.0828.The gene diversity(Fis)among different types fluctuated between 0.0642 and 0.5384,with an average of 0.2094.The genetic differentiation coefficient(Fst)ranged from 0.0529 to 0.2471,with an average of 0.1261.Gene flow(Nm)ranged from0.5538 to 2.7682,with an average of 1.4690.The genetic distance ranged from0.0473 to 0.4580,and the genetic consistency ranged from 0.6165 to 0.9605.Using the genetic distance matrix between different types of wild tea trees,clustering according to the UPGMA method,the Sichuan wild big tea trees are divided into two groups.The results showed that there was little variation within the same type and some genetic differentiation among the different types of the main wild tea plants in Sichuan.The genetic distances between the different types of wild big tea plants in Sichuan and the wild big tea plants in Yunnan ranged from 0.3545 to 0.4377,indicating that the major wild big tea plants in Sichuan and the wild big tea plants in Yunnan had large genetic distances,large gaps in genetic background,and were distantly related.(4)In summary,the major wild tea germplasm resources in Sichuan have complex genetic backgrounds,abundant traits,and high levels of genetic variation,which have high breeding potential and exploitation value.The evolution of wild tea plants in Sichuan is higher than that of the wild tea plants in Lincang,Yunnan.