Analysis Of The Evolutionary Origin And Spread Trajectories Of Camellia Sinensis In Fujian Province Based On Simplified Genome Sequencing

Fujian is an important tea-producing area in China,which is rich in tea germplasm resources.However,due to cross-pollination and inbreeding decline,the genetic foundation is single,making it difficult to select and grow new tea tree kinds.Aroma is a crucial indicator impacting the quality of tea leaves,and the kindred of tea tree varieties is an important basis for the selection and breeding of new variations.As a result,70 tea germplasm resources from 13 provinces,including Fujian Province,were sequenced by RAD-seq,and the volatiles of fresh tea leaves were detected by GC-MS,in order to investigate the genetic relationship of tea germplasm in Fujian Province and the key factors affecting the formation of tea aroma quality.As a result,70 tea germplasm resources from 13 provinces,including Fujian Province,were sequenced by RAD-seq,and the volatiles of fresh tea leaves were detected by GC-MS,in order to investigate the genetic relationship of tea germplasm in Fujian Province and the key factors affecting the formation of tea aroma quality.We examined tea variety relatedness,selection pressure,and volatile matter association analysis using the SNPs derived from the sequencing data,and mined tea tree aroma-related candidate genes and SNP sites.The main results of this study are as follows:1.RAD-seq sequencing revealed a total of 60,258,975 SNP sites in70 tea germplasm pools.Tea plants in Fujian were closer to those in northern Fujian,Taiwan outside Fujian and southern and northern Fujian,Zhejiang,Sichuan,and eastern Fujian,Hunan,Anhui,and northern Fujian,and there was a close relationship between Fujian and tea germplasm resources in many regions,according to the results of phylogenetic tree,principal component,and population structure analysis.2.70 tea germplasm resources were classified geographically into Fujian,East China,South China,Central China,and Western China.According to RAD-seq sequencing,Fujian has the most SNPs in tea varieties.Nucleotide diversity was less than 0.5 percent in all regions,with tea varietals in Fujian and South China having the highest nucleotide diversity.Tea plant FST levels in Fujian,East,and West China were all less than 0.05,with the lowest FST value in East China being 0.02,and the highest FST value in South China being 0.07.The neutral test Tajima’s D revealed that all locations were negative,with the exception of Central China.The number of selected genes in East China,South China,Central China,and West China was found to be 202,158,295,and 180,respectively,based on selection pressure analyses.The selected genes were mainly involved in plant hormone signal transduction,plantpathogen interaction,phenylpropane biosynthesis,fatty acid biosynthesis,respiration,and photosynthesis,and were enriched in respiration,photosynthesis,and metabolic pathways,according to the results of GO and KEGG enrichment analysis.3.The content of volatiles in fresh leaves of tea plants was determined using GC-MS,and it was discovered that the volatiles in different tea trees had a little difference in species but a huge difference in content.The most abundant compounds in fresh leaves were 3-carene,cis-3-hexen-1-ol,and(E)-4-hexene-1-ol.Alcohols and hydrocarbons dominate the fresh leaves of tea tree kinds,and these two volatiles primarily present flower and fruit scent,accounting for varying proportions in aroma components of different tea tree species.Clustering revealed that the volatile components and contents of Fujian tea varieties were similar to those of Sichuan,Zhejiang,and Anhui tea varieties,as well as the volatile components of tea varieties from the same region.The results of OAV,PCA,and OPLS-DA analysis revealed that volatile compounds could effectively distinguish tea varieties in different regions,with the aromas of tea varieties in eastern Fujian,northern Fujian,and Zhejiang being similar,as well as the aromas of tea varieties in southern Fujian and western Fujian.4.The tea plant’s LD decay rate was faster,according to the results of linkage disequilibrium study.The results of association analysis of volatiles in fresh tea leaves showed that there were 438 candidate genes and aroma metabolism pathway-related genes,of which there were 5multi-trait-related genes,namely pyruvate decarboxylase gene PDC4,terpenoid synthase gene TPS10,3-decarboxylase gene Hydroquinate dehydratase/shikimate dehydrogenase gene EMB3004,protoporphyrinogen oxidase gene PPXII and dihydroflavonol 4-reductase gene NGR＿a02300,these genes may be involved in the stress response of tea plants and affect tea quality.5.The combined analysis of selection pressure and GWAS showed that among the selected genes in South China,5 genes were significantly associated with α-farnesene,5 genes were significantly associated with 3-carene,and 5 genes were significantly associated with(E)-4-hexene.4genes were found to be significantly linked to-1-ol,whereas 8 and 9genes were found to be significantly linked to linalool oxide II and methyl salicylate,respectively.The results of the GO enrichment analysis revealed that the majority of the volatile-associated genes under selective pressure were involved in metabolic activities and cell-related pathways.There are also three genes linked to the two volatiles.These genes may be involved in the production of scent,which is the secret to the aroma variances between tea kinds grown in the two locations.