西双版纳地区流苏石斛遗传多样性的ISSR分析

采用ISSR分子标记技术，对西双版纳分布的兰科濒危植物流苏石斛（Dendrobium fimbriatum）5个居群共114个个体的遗传多样性进行了研究。从100条引物中筛选出了12条用于扩增，共检测到117个位点，其中105个为多态位点。分析结果表明，流苏石斛居群水平遗传多样性较低。在物种水平上，流苏石斛多态位点百分率PPB为89．74％，Nei’s基因多样性指数日为0．3227，Shannon’s多样性信息指数见。为0．4779；在居群水平上，各个居群的多态位点百分率PPB差异较大（6．84％～39．32％），平均值为23．93％，Nei’s基因多样性指数H为0．0871，各个居群的Shannon’s多样性信息指数见平均为0．1290。AMOVA分析的结果显示，流苏石斛的遗传变异大多数存在于居群间，占总遗传变异的74．79％。基于Nei’s遗传多样性分析得出的居群间遗传分化系数Gst=0．7443。各居群间的Nei’s遗传一致度（I）范围为0．5882～0．8331。Mantel检测发现，居群间的遗传距离和地理距离之间无显著的正相关关系（r=0．2419，P=0．2416）。鉴于流苏石斛的遗传多样性现状和居群遗传结构，我们建议对流苏石斛居群所有个体实施及时的就地保护，同时建立迁地保护居群，促进基因交流。

Genetic Diversity of Dendrobium fimbriatum (Orchidaceae), an Endangered Species, Detected by Inter-simple Sequence Repeat (ISSR)

The genetic variability of five populations from xishuangbanna were investigated using inter-simple sequence repeat （ISSR）. A total of 117 unambiguous and repetitious bands were obtained from 114 individuals of sampled populations using twelve primers selected. The results showed that Dendrobiumfimbriatum exhibited a relatively low genetic diversity at population level. At species level, the value of the average percentage of polymorphic bands （PPB） was 89.74%, expected heterozygosity （H） was 0.3227, Shannon＇s Information index （Hsp） was 0.4779; while at population level, the value of the average percentage of pelymorphic bands （PPB） was 23.93%, expected heterozygosity （H） was 0.0871, Shannon＇s lnformation index （Ho） was 0. 1290. Most of genetic variation partitioned among populations （74.79%）. The coefficient of gene differentiation among populations （ Gst ） was 0. 7443 showed that genetic diafferentiation among population based on Nei＇s genetic distance had a high degree. Pairwise genetic identity （1） among populations ranged from 0. 5882 to 0. 8331. No significant correlation was found between geographical and genetic distance. Based on the findings in present study, we proposed that conservation management of Dendrobium fimbriatum shoud include protection of nature habitats occupied by all five wild populations and preservation of germplasm in botanical gardens from multiple seed sources to accelerate the gene flow.