Abstract: 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 Dendrobium fimbriatum 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 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%). 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 ( I ) 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 .

Key words: Dendrobium fimbriatum