Genetic Diversity Of Larix Principis Rupprechtii Revealed By SSR Marker

Larix principis rupprechtii belonging to larix in pinaceae, was a main forest species in mountain areas in northern China. Due to the fast growth, good material, extensive using, resistance to decay and other advantages, it is an ideal forest tree species for economic and ecological value, at the same time, for the good ability of water storage, it was also a good shelter forest species. Now, the natural populations of Larix principis rupprechtii was conditioned to several mountains, and distributed dispersedly. This habitat fragmentation will reduce the level of genetic diversity. Understanding the genetic diversity and population structure of Larix principis rupprechtii populations not only provides insights into breeding program of this species, but also help the conservation and management strategies for endangered species.This study selects the EST database of larix and several other species from pinus. We used the EST sequence to design SSR primer after the EST sequence has been eliminated redundancy and assembled.We have developed14SSR polymorphic primers.10of14were used to evaluate the genetic diversity and population structure of a total of704Larix principis rupprechtii which were from20natural populations.(1) A total of140EST-SSR primers were designed and synthesized.18of140was from larix,79was from Pseudotsuga,21was from scots pine,22was from Abies. There was57out of140primers having amplification products, accounting for40%.32primers have clear and stable amplification products, but only14was polymorphic primers, accounting for10%.(2) Based on704samples of10natural Larix principis rupprechtii Mayr populations in North China, ten pairs of SSR primers were utilized to study the genetic diversity and population structure of these populations. A total of54alleles were detected, with a mean of5.4bands per primer, and the alleles of each locus (Na) were2-8. The mean Shannon’s information index (I) was0.787, and the observed heterozygosity(Ho) and expected heterozygosity (He)were0.393and0.424, respectively. Among the20populations, Wangyedian represents the highest level of genetic diversity,reaching0.549, Taizishui and Jizi from Weichang county and Wuling mountain populations which were all located in the north of Hebei had the second highest genetic diversity. Wangyedian and Weichang were the far north of natural populations distributing. While, the populations from the central and south of Shanxi province have the lowest genetic diversity, Kelan (He=0.285)、 Dujiacun (He=0.350)、Yundingshan (He=0.329)、Xiaowenshan(He=0.278)and Mianshan (He=0.325) were from the central and south of Shanxi province. Fuping (He=0.371) and Longhua (He=0.388) from Hebei province were also relatively low. The AMOVA analysis showed that the percentage variation among the populations was6%, while the percentage variation within the populations was94%, and Gst was only0.046, illustrated that the genetic differentiation was quite low.(3) Clustering result showed that, based on the threshold value of0.028, the20natural populations can be divided into5subgroups, the Wangyedian, Baihuashan, Qinyuan population were alone for a subgroup respectively. Yanggao, Kalan, Yundingshan, Xiaowenshan, Dujiancun, Mianshan populations make up a subgroup, this were main from the central and south Shanxi. Others mainly from Hebei province, Beijing and Hunyuan,Wutai from northern Shanxi was a subgroup.(4) The northern population have a higher diversity than south,and it has a degressive trend from north to south. It shows that the direction of evolution was from north to south, and heterozygosity in south extension process has a certain loss. Otherwise, there was interspecies gene communication in the north, and Larix principis rupprechtii may be a new species resulting from the evolution of Larix gmelinii, it confirm previous research.