Abstract: [Objective] As a precious broadleaf timber and an efficient tree species for biological fire prevention, Schima superba plays an important role in commercial timber production forests and ecological fireproof forest construction. In depth studies of genetic diversity of S. superba plus tree clones using SSR markers are particularly important for conservation, utilization of genetic resources, and future breeding programs for this plant species. [Method]A total of 734 clones of S. superba plus trees from 24 areas of five provinces in China, were analyzed systematically with 10 SSR primer pairs. The GenAIEx 6.5 and CERVUS software were used for genetic diversity parameters calculation, principal coordinates analysis (PCoA) and null alleles detection. NTSYS software was used for cluster analysis based on the matrix of Nei’s genetic identity. The Arlequin software was used for analysis of molecular variance (AMOVA). STRUCTURE 2.3 software was used to analyze genetic structure. [Result]The results showed that 105 alleles were detected among the germplasm accessions, with an average of 10.5 alleles per pair of primers. The maximum number of alleles was detected in primer ss16 with a value of 16. The Shannon’s information index (I) was ranged from 1.121 to 1.908, with an average of 1.473. The polymorphism information content (PIC) was ranged from 0.557 to 0.807, with an average of 0.668. The expected and observed heterozygosity were 0.713 and 0.735, respectively. The results of principal coordinate analysis (PCoA) and genetic structure analysis were basically consistent with each other, the 734 clones were divided into three groups in PCoA or five subgroups in STRUCTURE analysis. The genetic distance of 24 populations were ranged from 0.030 to 0.804, with an average of 0.230. The results showed that there were close genetic relationship between populations, but, there were still larger genetic distances between some populations, such as HNSZ and GDSX, JXFY and FJSX, etc. The Shannon’s information index (I) of populations were ranged from 0.980 to 1.431, and the genetic diversity was not significantly correlated to geographic distribution. The results of genetic structure analysis indicated that 71.1% S. superba plus tree clones displayed a simple genetic structure, and the rest 28.9% displayed a mixed genetic structure. The AMOVA results showed that the differentiation among populations contributed to 5.91% of the total genetic variation, and the differentiation within populations contributed 94.09% of the total genetic variation.[Conclusion] All the results showed that there was a high level of genetic diversity in S. superba plus tree germplasms, and a significant difference of genetic diversity among populations. When selecting mating parents,the mating pairs should be geographically distant, and genetic relationship between populations or individuals should also be taken into account.

Key words: Schima superba, plus tree, SSR markers, genetic diversity, genetic structure