Studies On Genetic Diversity And Relationship In Tea Varieties Grown In China Based On Ssr Markers

Tea(Camellia sinensis (L.) O. Kuntze) is a time-honored non-alcoholic beverage with the tea plant being widely cultivated in more than50countries and regions, mainlly in Asia and Africa. Research proves that the southwestern part of China is the original center of tea plant, teeming with diverse and abundant tea germplasm resource critical for laying the foundation for tea plant breeding. A great number of varieties have been bred which hold n3umerous advantages, such as high quality and yield, and resistance to disease and insect pest, which are the firm basis of Chinese contemporary tea industry. According to the statistics, by the year of2005,97varieties were examined and approved by state government and120odd varieties by provincial governments. Notably, clonal varieties play a dominant role and greatly propel the process of extension of improved varieties in China. Therefore it is necessary and significant to understand genetic variation and relationship in tea varieties so as to guide the tea breeding work in the future. DNA markers are proved to be powerful tools universally applied in estimating the genetic diversity and relationship in tea plant. With the development and application of SSR in tea plant studies, researches on the molecular biology and genetics of tea plant are increasingly active and productive.This research sought to evaluate the genetic diversity and relationship in tea clonal varieties and strains in China in order to obtain comprehensive insights into thesis varieties.40SSR primer pairs with polymorphism, including39new primer pairs were used to analyze genetic diversity and relationship of oolong tea varieties and strains. In total,179alleles and329genotypes were amplified by the40SSR markers, at an average of4.48and8.23per marker. The average polymorphism information content (PIC) was0.52while Gene diversity(H) and genetic distance were0.57and0.59, respectively. The results showed a relatively high level of genetic variation among the46samples tested. Tea varieties from Guangdong province had higher genetic diversity than those of other provinces, but the level of genetic diversity of cultivars bred by crossing-pollination was lower than those bred through other methods. Almost all the tested varieties and strains were clustered according to their geographic source and breeding source using both UPGMA and PCA method.39new SSR primer pairs with polymorphism were used in analysis of genetic diversity and relationship of green and black tea varieties and strains in this study. The results showed a relatively high level of genetic variation among159tested samples. A total of191alleles and440genotypes were amplified by the39SSR markers, with the average per marker being4.9allels and11.28genotypes. The average polymorphism information content (PIC) was0.53while Gene diversity (H) and genetic distance were0.57and0.64, respectively. Guangdong province had tea varieties with higher genetic diversity than teas from other provinces. In addition, the level of genetic diversity among cultivars bred by individual selection was higher than that in varieties bred through other methods. Almost all the tested varieties and strains were clustered according to their geographic source and breeding source using UPGMA. The genetic diversity of derived varieties from Fuding-dabaicha and Yunnan-dayecha was relatively high with a wide range of genetic distance.To analyse of genetic diversity and relationship of Chinese clonal tea varieties,58SSR primer pairs with polymorphism including56new primer pairs were used. The results showed a relatively high level of genetic variation among185tested samples (H=0.54) with the average genetic identity being0.57. The Clonal varieties from Guangdong province also had a higher genetic diversity than those from other provinces and a higher level of genetic diversity among green and black cultivar was evident than in oolong tea varieties. All the varieties classified according to its partial botanic features and the result showed that the genetic diversity among these groups included, semi-treescent form varieties>shrub form varieties>arbor form varieties; large leaf varieties>medium and small leaf varieties; early sprouting varieties>medium sprouting varieties>late sprouting varieties. Most of the tested varieties were clustered according to its geographic source and breeding source using both Mathematic Simulation Model and UPGMA methods.