| Bupleurum dracaenoides is a rare and unique plant with xylem stem of Apiaceae.It is the only plant in Asia with a woody stem,occured with low population density in Jinshajiang River valley.The population size of B.dracaenoides is decreasing year by year,but the factors influencing its declines are unknown.In order to protect B.dracaenoides,full and further research are necessary.We adopted transcriptome sequencing,SSR,and ISSR molecular marker technique to analyze the genetic diversity of 163 samples from 9 B.dracaenoides populations.We explored the genetic diversity pattern among the populations of B.dracaenoides.The main results of this study were as follows:1.126 EST-SSR primers were developed,and there are 89 effective primers.26 primers were polymorphic among 89 primers.The EST-SSR loci frequency of B.dracaenoides was at the middle level in Apiaceae or other genera.Like most plants,the main type was dinucleotide repeats.The rate of polymorphism on EST-SSR primer was 24.71%,Thirteen alleles were observed.2.36 effective primers were obtained from 100 ISSR primers,and 22 primers were polymorphic.The genetic similarity coefficient was from 0.8539 to 0.9540,and the genetic distance is from 0.047 to 0.1580.Population genetic diversity among populations were Sanjiacun(0.3161)> Sankeshu2(0.2715)> Xinkeda1(0.2681)> Xinkeda2(0.2315)> Pumiehoushan(0.2113)> Baishiyanjing(0.2075)> Pubu(0.1392)> Sankeshu1(0.1382)> Jiudaowan(0.1007).3.By cluster analysis,due to geographical source,genetic background,human interference of different,the populations were divided into three groups when the genetic simlarity coefficient was less than 0.92.Group 1 included Baishiyanjing and Xinkeda 2;Sankeshu 1 and 2,Pubu,Pumiehoushan,Jiudaowan;Group 2 and group 3 are three Sanjiacun and Xinkeda 1 respectively.In general,9 population split into two branches,Pubu and Xinkeda population in one,the other seven populations were another branch.Genetic variation of within population was 92% from AMOVA result.There was no significant correlationship between population geographical distance and genetic distance.4.In the 9 populations,the observed allele number was 1.4803 and the effective allele was 1.38,i.e.Nei’s genetic diversity index was 0.2093,Shannon’s polymorphism information index was 0.3007.Gene flow indicated by Nm was 1.6777.The Genetic differentiation coefficient was 0.2305.The frequency of gene communication was high,The genetic differentiation was small,Genetic drift was not the main factor affecting the genetic structure.B.dracaenoides populations had low genetic diversity Genetic variation mainly existed within population.The results show that EST-SSR primers are effective and can be used for SSR related research in the future.The low genetic diversity may be the main reason for the decrease of B.dracaenoides populations.Combined with previous studies and the results of this paper,these measures can be taken to protect it:(1)Main populations of B.dracaenoides should be protected in situ.(2)Grazing and habitat destruction should be forbid to keep stability of population regeneration.(3)Besides,wild population should be enlarged by rehabilitation of artificial breeding individuals.(4)Conservation of seed resources in main populations with high genetic diversity should be implemented by means of seed collection and setting up permanent protected sites. |
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