| Lacquer tree,or Toxicodendron vernicifluum(Stokes)and Taxus Linn.are the two most important threatened species in Vietnam.Up to now,the genetic diversity and structure diversity of the wild populations was rarely explored due to the lack of reliable and informative molecular markers of Chinese lacquer and Vietnam conifer species.To provide guidelines for the conservation,management,and restoration of these species especially in China and Vietnam,this research evaluated the level and structure of genetic diversity of major cultivated varieties and natural populations of Chinese lacquer(T.vernicifluum)and two Taxus species in Vietnam,and disclose the mechanism of genetic erosion under the effect of human activities.The results of study as follow:1.A total 20 074 230 sequencing reads were generated by Illumina HiSeq? 2500 from three different Toxicodendron vernicifluum tissue samples.A total of 48 693 unigenes were identified from a de novo assembly and 486 microsatellite loci were isolated(GenBank code:KU947470 to KU947955).There were 150 pairs in the determined SSR loci that were selected to test the primer amplification efficiency.Among them 40 primer pairs yielded polymorphic amplification products.Using these SSR primers,it was revealed that natural populations of T.vernicifluum maintained a high level of genetic diversity.Microsatellite markers for T.vernicifluum developed in the present study will provide a platform for the study of genetic diversity,species identification,understanding of the population structure,conservation and breeding of T.vernicifluum.2.The level of genetic variability within and among lacquer cultivars were investigated to provide guidelines for the conservation,management and restoration of this species.Gaobazhi cultivar had greater genetic diversity(Ne = 1.899,I = 0.638,Ho = 0.612 and He =0.410)as compared to Huangmaoguizhou(Ne = 1.878,I = 0.643,Ho = 0.568 and He = 0.418),Huangrong(Ne = 1.710,I = 0.538,Ho = 0.555 and He = 0.356),Dahongpao(Ne = 1.659,I =0.466,Ho = 0.573 and He = 0.322)and Damu(Ne = 1.536,I = 0.468,Ho = 0.315 and He =0.297),with an average of 1.736,0.55,0.525 and 0.361 respectively.Genetic differentiationamong cultivars was high(Fst = 0.427 to 0.526),indicating limited gene flow(Nm = 0.278).AMOVA showed low genetic variation within cultivars(46%)compared to among cultivars.The unweighted pair group method average(UPGMA)detected the optimal five clear clusters.Gaobazhi cultivar is closer to the group containing the Dahongpao and Huangrong cultivars than Damu and Huangmaoguizhou cultivars.3.Taxus chinensis and T.wallichiana have been threatened in their distribution areas.Determining the genetic diversity in populations of two species will provide guidelines for their protection and preservation.Among the 13 putative alleles amplified,11 were polymorphic(accounting for 76.33 %).Shannon's information index(I)and percentage of polymorphic bands(PPB)(I = 0.202 and PPB = 67.22 % for T.chinensis;I = 0.217 and PPB= 65.03 % for T.wallichiana).Both species had low levels of genetic diversity(mean Ho =0.107,He = 0.121 for T.chinensis;Ho = 0.095,He = 0.109 for T.wallichiana).Genetic differentiation among populations was higher(Fst = 0.189)for T.chinensis and lower(0.156)for T.wallichiana,indicating limited gene flow(Nm)among populations for T.chinensis(0.68)and T.wallichiana(0.65).Thus,the threatened status of the two conifers is related to a lack of genetic diversity.All populations are isolated in small forest remnants.An ex-situ conservation site should be established with a new population for these species that comprises all the genetic groups for the best chance to improve their fitness under environmental stresses. |
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