Analysis On Genetic Diversity And Genetic Structure Of Cyclobalanopsis Gilva Population

Cyclobalanopsis gilva is an evergreen tree of Fagacea Cyclobalanopsis, which is one of the excellent commercial tree species with straight trunk, hard materials in China. Cyclobalanopsis gilva has high economic and ecological values. It has been listed as the second-level protected plant by China. In this paper, inter-simple sequence repeat (ISSR)markers was used to analyse the genetic diversity and genetic structure of140individuals among7populations from Hunan and Zhejiang Province of Cyclobalanopsis gilva, which would provide theoretical basis for effective protection, rational utilization and genetic improvement strategy formulation of genetic resources of Cyclobalanopsis gilva. The main method and results are as follows:(1) The optimal ISSR reaction system suitable for Cyclobalanopsis gilva was found.Through the single factor test, the five main factors(template DNA, dNTPs, Mg2+, Taq DNA polymerase,primer)affecting ISSR-PCR reaction for Cyclobalanopsis gilva were researched to determine the optimum concentration range for each factor, then through orthogonal design test and intuitive analysis, the optimal system of ISSR-PCR reaction was established as follows:20ng template DNA,0.2mmol/L dNTPs,2.5mmol/L Mg2+,0.2μmol/L primer,1.OU Taq DNA polymerase were contained in20μL reaction system.On this basis, the optimal amplification program was established.(2) Based on the optimized reaction system,13primers with rich polymorphism and stable amplification for ISSR-PCR were screened from100primers.With13selected primers,111polymorphic loci were detected from total140loci,the total percentage of polymorphic band(P)was79.29%. At the population level with the percent of polymorphic bands ranged from61.42%-75.00%,DK was the highest and SZ was the lowest. At species level of Cyclobalanopsis gilva Shannon’s information index (Ⅰ) was0.4514and Nei’s gene diversity (h) was0.3021. At the population level with the Shannon’s information index (Ⅰ) and the Nei’s genetic diversity index(H) ranged from0.3234to0.4193and0.2164to0.2871.At population level,the genetic diversity of JZ was highest and CZ was lowest.(3) Coefficient of genetic variation among Cyclobalanopsis gilva populations(Gst) was0.0613, so the great majority of genetic variation consist in populations and it was93.87%.The gene flow was3.8283(Nm>1) which was sufficient to prevent genetic drift and maintained the similarity among populations.(4) The analysis of the genetic distance of the7populations showed that it correlated with the geographic location.At the population level with the genetic distance (D) ranged from0.0260to0.1596.The genetic distance between YD and CZ was the lowest,while the numerical value between JZ and QY was the highest.These results showed that the geographical distance was the major factor which influenced the genetic variation.(5) The genetic diversity and genetic structure analysis of available7populations showed that the main reason causing Cyclobalanopsis gilva decreasing was because of human influence, habitat destruction but not genetic variations. Conservation strategies for extant populations were proposed based on them,such as:improve foresters’ awareness of protecting forests,establishing reserve, conducting deeper research on the species,establishing germplasm repository.