Analysis Of Population Genetic Structure And Estimation Of Conservation Strategy Of Dendrobium Fimbriatum (Orchidaceae) From Xishuangbanna

Dendrobium fimbriatum (Orchidaceae) is an endemic and endangered species in China. It can be used as ornamental and medicinal plant.The biological charaters of the species, habitat fragmentation, especially rubber planting, have caused decline of population size of the species. ISSR were used to investigate the genetic diversity and genetic structure of five natural populations (114 individuals) of the species, in order to put forward scientific conservation strategy.For five natural populations, twelve primers of ISSR produced a total of 117 unambiguous and repetitious bands, of which 105 (89.74%) were polymorphic. The results showed that Dendrobium fimbriatum exhibited a comparatively low genetic diversity: 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; at population level, the value of the average percentage of polymorphic bands PPB was 23.93%,expected heterozygosity H was 0.0871,Shannon's Information index Ho was 0.1290. Most of genetic variation partitioned among populations (74.79%). Genetic differentiation among populations had a high degree: the coefficient of gene differentiation among populations Gst was 0.7443. Pairwise genetic identity (I) values among populations ranged from 0.5882 to 0.8331. No correlation was found between geographical and genetic distance, which indicated gene flow may be influenced by complicated local landform or insect pollination and animal-madiated seed dispersal. On the basis of ISSR marker analyses, recent habitat fragmentation may have led to the loss of genetic diversity or genetic differentiation in the endangered species.Based on the above findings, we propose that conservation management of Dendrobium fimbriatum shoud include protection of natural habitats occupied by all five wild populations and preservation of germplasm in botanical gardens from multiple seed sources. More populations should be selected whenever ex situ or in situ conservation strategies are taken.