我国茶树无性系品种遗传多样性和亲缘关系的ISSR分析

利用ISSR分子标记分析了我国36个主要茶树无性系品种的遗传多样性和亲缘关系。结果表明20个ISSR引物在供试品种中共扩增出368条谱带，其中多态性条带占总条带的99.7%，引物的多态性信息指数（PIC）平均达0.90。供试品种的基因多样性（H）和Shannon信息指数（I）分别为0.23和0.38。茶区内茶树品种的遗传多样性低于总体水平，江南和华南茶区主栽无性系品种的多样性高于西南茶区。AMOVA分析表明区域因素引起的变异（占5.6%）远小于品种因素（占94.4%）。供试品种间的相似系数介于0.58~0.84，平均为0.69，显示出我国茶树主栽品种的遗传基础已相对比较狭窄。ISSR聚类分析表明，中国台湾品种金萱与大陆品种的遗传距离较远，形成单独的个类。35个大陆品种聚成一个大类群，其中除宜红早形成独立的个类外，其他品种又聚为3个亚类群。亲缘关系树状图在分子水平上显示了我国主要茶树无性系品种间的亲缘关系，为今后茶树育种亲本的选配提供了理论依据。

Genetic Diversity and Relationship of Clonal Tea Cultivars in China Revealed by ISSR Markers

Tea is an important beverage crop in China. In recent years many clonal tea cultivars have been developed and widely replaced the diverse traditional tea population. Our knowledge on genetic diversity and relationship of these clonal tea cultivars is critical to guide tea breeding, but still limited. In this study, the genetic diversity and relationship of 36 clonal tea cultivars which mainly cultivated in China were analyzed with ISSR markers. Based on 20 ISSR primers, total 368 bands were generated, of which 367 (99.7%) were polymorphic. The average polymorphism information content (PIC) was 0.90, Nei’s gene diversity (H) and Shannon’s information index (I) were 0.23 and 0.38, respectively. Diversity of clonal cultivars within tea area was lower than that of in whole nation. The levels of diversity in Tea Area of Jiangnan and South China were higher than those of Southwest China. Analysis of molecular variance (AMOVA) showed that variance component among cultivars (94.4%) was far higher than that among regions (5.6%). The genetic similarity among all the tested clonal cultivars ranged from 0.58 to 0.84, averaging 0.69, which indicated that the genetic basis was relatively narrow. The cluster analysis based on ISSR markers revealed that cultivar “Jinxuan” from Chinese Taiwan was of the farthest distance with others from Chinese mainland in the dendrogram. Thirty-five clonal cultivars from Chinese mainland were clustered into a major group, and they could be further classified into three sub-groups except cultivar “Yihongzao”. The genetic relationship of all 36 tea cultivars revealed by the ISSR dendrogram would be of great help to accurately select the parents in tea breeding programs.