Genetic Structure Of Rhododendron Dauricum Natural Populations Assessed By SSR Markers

The genetic diversity and genetic structure of species that are formed in the long evolutionary process reveal the genetic background,evolutionary potential,utilization value and have important implications for the conservation and utilization of fine species.Rhododendron dauricum is a semi-evergreen shrub,it is widely distributed in northeast China.Because it has medicinal value,the current study concentrated on chemical composition and pharmacological studies etc.However,research on its genetic structure is rarely reported.Therefore,we employed seven pairs of SSR(Simple sequence repeats)molecular markers to infer genetic diversity and genetic structure for Rhododendron dauricum from the Daxing'anling,xiaoxing'anling,Changbai Mountain and the Liaodong Peninsula region.153 individuals from 21 natural populations were analysed.At the molecular level,To assess the extent of genetic diversity and differentiation among populations;understand the phylogenetic relationship of groups;discuss the influence of geographic isolation and breeding systems on genetic structure.The results showed that seven pairs of microsatellite loci were detected 104 alleles,of which 20 alleles were specific to different populations.Polymorphism information content(PIC)was ranged from 0.2246 to 0.8879.The average percentage of polymorphic loci was 85.71%.The mean observed heterozygosity was 0.4507.the result indicated the Rhododendron dauricum has high level of genetic diversity at the species level.Genetic differentiation among populations Fst was 0.2089,it revealed that there was obviously differentiation among populations.AMOVA analysis indicated that most of genetic variation were observed within populations,accounting for 78.44%.Gene flow(Nm)among populations was smaller for 0.6314.Alpine barrier,climate differences,insect-pollinated,small gene flow were likely to lead to genetic differentiation increases.Mantel test revealed that a significant correlation between genetic distance and geographic distance(r=0.2635,p?0.0500).STRUCTURE and phylogenetic tree analysis show the closer geographical groups were firstly clustered.This further confirmed the effect of geographical isolation on genetic differentiation among populations.Bottleneck analysis showed that 40% population(BY,WL,KD,LJ,SJ,HS,JH,TP)experienced a recently genetic bottleneck.These results contribute to a preliminary understanding of the genetic structure and dynamics of Rhododendron dauricum populations.It has important implications for the conservation of Rhododendron germplasm.