| Tea contains a broad group of Camellia tea (Camellia L. Sect. Thea (L.) Dyer) of many species and varieties, including wild relatives, landraces, cultivars, strains. Tea germplasms are important for tea breeding and tea production. In this research, using phenotypic characteristics and leaf SSR molecular markers, genetic diversity of 554 tea genotypes and their relationships were studied.The phenotypic characteristics and molecular variations of the tea genotypes from 14 tea growing regions of China were analysed. From the result, the genetic structure and level of genetic variation of the tea genotypes from the different regions were revealed. The coefficient of variation for leaf characteristics among the 406 tea genotypes studied were in the order: leaf cross section > leaf color > leaf texture > leaf area> leaf upper surface. The Shannon-weaver diversity indices for leaf characters were in the same order. This indicated that leaf cross section had wider variations than other characters, and leaf upper surface was relatively stable. The phenotypic variations of wild tea, landraces were high than cultivars. It indicated the variation of cultivated tea had been reduced to a certain extent over time owing to human selection. The average coefficient of variations and Shannon-weaver diversity indices for leaf characters for the 14 regions were compared. The values for Southwest and South China were relatively higher than other areas.Tea genotypes from Guangxi and Yunnan were most genetically diverse, this corroborated wide phenotypic differences observed among the different tea genotypes studied. The genetic diversity of tea genotypes from Guangdong, Guizhou, Chongqing, Sichuan and Hubei were more higher, while those from Hunan, Henan, Jiangsu and Anhui were lowest. It was deduced that the genetic diversity of tea germplasms presents a spatial distribution of the following features: there was a gradual reduction in genetic diversity from Yunnan and Guangxi to the east sector, also from the south to the north. The Neighbor-Joining Dendrogram based genetic distance and cluster analysis of genetic structure of 554 tea genotypes studied showed that Yunnan tea genotypes had a relatively independent structure, clustered into a separate category but some of its resources were distributed in other regions. The tea germplasms of Guangxi, Guizhou, Chongqing and Guangdong mostly were clustered together; Sichuan and Hubei clustered together; Anhui, Fujian, Jiangxi, Zhejiang, Jiangsu, Henan and Hunan tea germplasms clustered together as a category. This showed that germplasms from the same regions were mostly clustered together, but there were germplasms of different types and different geographical origin interspersed in the cluster group. The average inbreeding coefficient among the 14 regions was 0.23, indicating the phenomenon of inbreeding within the regional group was very serious. The average of coefficient of genetic differentiation between regions was 0.14, indicating that 14% of the genetic variation between regions, while 86% of the genetic variation within populations. The gene flow among populations of tea germplasms based on the F- value was 1.54, which showed that gene flow was very frequent among different regions. And it led to heterozygosity deficiency.The level of genetic diversity was in the order: wild tea > landraces > cultivars. It showed that artificial selection had caused slight decrease in genetic diversity, especially in the cultivars. The coefficient of genetic differentiation between among the tea genotypes was 0.05, indicating that 5% of the genetic variation was among groups, 95% of the variation existed within groups.
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