Panax vietnamensis Ha et Grushv. is a precious medicinal species native to the tropical forests of Vietnam. Due to habitat loss and over-harvesting, this species is endangered in Vietnam. To conserve the species, we investigated genetic variability and population structure using nine microsatellites for 148 individuals from seven populations across the current distribution range of P. vietnamensis in Vietnam. We determined a moderate genetic diversity within populations (HO = 0.367, HE = 0.437) and relatively low population differentiation (the Weir and Cockerham index of 0.172 and the Hedrick index of 0.254) and showed significant differentiation (P < 0.05), which suggested fragmented habitats, over-utilization and over-harvesting of P. vietnamensis. Different clustering methods revealed that individuals were grouped into two major clusters, which were associated with gene flow across the geographical range of P. vietnamensis. This study also detected that ginseng populations can have undergone a recent bottleneck. We recommend measures in future P. vietnamensis conservation and breeding programs.

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AFLP -amplified fragment length polymorphism; AMOVA -variance components molecular variance; CR -critically endangered; DAPC -discriminant analysis of principal components; FIS -fixation index; FISIIM -corrected inbreeding coefficient for null alleles; HE -expected heterozygosity; HO -observed heterozygosity; HT -total expected heterozygosity; HWE -Hardy-Weinberg equilibrium; ISSR -inter simple sequence repeat markers; IUCN -international union for conservation of nature; NA -alleles per locus; NE -effective alleles; NJ -neighbor-joining; NP -private alleles; NR -allelic richness; PcoA -principal coordinate analysis; PCRpolymerase chain reaction; PPL -proportion of polymorphic loci; RAPD -random amplified polymorphic DNA; SMM -the stepwise mutation model; SSR -microsatellite; Tm -PCR annealing temperature; TPM -the two-phase model. Acknowledgements: This research was funded by Vietnam national Foundation for Science and Technology Development (NAFOSTED) under grant number 106. 06-2018.310.