| Camphor tree(Cinnamomum camphora),as a Tertiary tree species,is widely distributed in subtropical evergreen broad-leaved forest and used in many applications,including garden greening,the material of essential oil and wood furniture.In recent years,however,the natural resources of camphor trees have declined quickly by the influence of human activities and environmental changes.The research on population genetics of C.camphora will reveal the genetic structure and clarify its evolution history,which may provide a scientific basis for the conservation strategy of camphor genetic resources,and a theoretical basis for the evaluation and utilization of camphor germplasm resources and the selection of breeding.The main findings are as follows:1.The selection of SSR primers.In this study,11 pairs of SSR primers with high amplification effectiveness and high sequence polymorphism were evaluated among 22 pairs of SSR primers from the previous research.Moreover,based on the transcriptome of linalool-chemo type of C.camphora,16 pairs of primers were designed with more than 10 dinucleotide repeats.9 pairs of SSR primers with clear bands,high PCR amplification and high polymorphism were selected.Therefore,a total of 20 pairs of polymorphic SSR primers were used to analyze the population genetic diversity of C camphora,including:Cc-A46,Cc-B25,Cc-B29,Cc-B91,Cc-C1,Cc-C87,Cc-C90,Cc-D88,Cc-A4,Cc-B89,Cc-B90,Cc-30,Cc-58,Cc-68,Cc-05,Cc-34,Cc-12,Cc-91,Cc-50,Cc-45.2.Genetic diversity based on SSR analysis.The 20 pairs were used to explore the genetic diversity of 241 individuals in 21 populations of C.camphor in China.A total of200 alleles were detected among 20 SSR loci,and the average number of effective alleles(Ne)was 7.114.The mean heterozygosity(Ho)was 0.977.The average expected heterozygosity(He)and polymorphism information content(PIC)were 0.7853 and 0.754,respectively.Camphor trees have a high level of genetic diversity(He=0.785).3.Genetic diversity in and between populations of C camphor.The average inbreeding coefficient within the population was-0.047,the average inbreeding coefficient Fit between populations was 0.067,and the average genetic differentiation level Fst between populations was 0.109.The genetic diversity of the ancient camphor population was higher and had moderate level of genetic differentiation.The minimum value of gene flow Nm in camphor population was 1.120(Cc-B90),the maximum value was3.972(Cc-12),and the average value was 2.047,indicating that higher gene flow hindered the occurrence of genetic differentiation between populations.There was a significant correlation between genetic variation of Ming population and geographical distance.The results of cluster analysis showed that 21 camphor tree populations were divided into four groups: southern,southwestern,middle 1 and middle 2.The genetic diversity was thehighest in the middle 1,but the rare alleles were abundant in the southern population.Attention should be paid to sample collection and in-depth study of the genetic structure of these marginal regions.4.Chloroplast gene haplotype analysis.In this study,nine large variant chloroplast gene fragments were selected to analyze haplotypes of camphor population.However,the selected gene fragments did not find any variation in the camphor tree population,and the sequence information of the tested population was identical.This indicates that the evolutionary history of camphor trees is complicated,and gene screening should be strengthened in the following studies,or genetic structure analysis in populations should be carried out with high-throughput techniques.The results can not only provide scientific basis for the protection of camphor resources and breeding resources,but also benefit the sustainable development and utilization of the genetic resources of camphor trees. |
PDF Full Text Request