Study On Molecular Phylogenetic Of Genus Tilia Linn And Conservation Genetics Of Tilia Miqueliana Maxim.

The trees of Tilia genus has great utilization value as timber species, ornamental trees, medicinal plants, nectar source plants, and related to religion culture. But few relevant researches of its origin and conservation have been published. The molecular phylogenetic of genus Tilia L. and conservation genetics of T. miqueliana were studied in this paper, the results were showed as follows:The ITS sequence can be used to analysis phylogenetic of Tilia L. The species of Tilia L distributed in European and North America may be originated from East Asia. The evolution of the species distributed in European was not only one path. The relation of three species distributed in North America was closer. The species distributed in East Asia has different evolutionary speed. The phylogenetic trees display difference by Neighbor- joining, Maximum parsimony and Minimum evolution analysis, but the changing trends are concident. The inter simple sequence repeats marker can be help to explain the genetic relationship of the species of this genus, but the TrnL_F sequence could not used to analysis phylogenetic of this genus.High level genetic diversity of T. miqueliana was detected by ISSR marker. At species level, the percentage of population polymorphic loci, Nei's genetic diversity and Shannon's information diversify index was 99.37%, 0.4510 and 0.6416. Nei's gene diversity and Shannon's index diversity showed that there were major genetic variations within populations, and the genetic difference was significantly among populations, the coefficient of gene differentiation was 0.2353 and the gene flow was 1.6245. The genetic distance between NSH population and other populations is higher, the UPGMA Dendrogram displayed that other seven populations clustered first, and then they clustered with the NSH population. The results showed the genetic distance didn't relate to geographic distance in eight populations of this species.The expressions of genetic information from the gene flow and genetic drift depended on seed propagation, so seed propagation had important effects on population genetic structure. The key and core of the genetic variation and genetic differentiation of T.miqueliana is the difficulty of seed propagation.The causes of the difficulty of T. miqueliana seed propagation is lower seed plumpness and seed dormancy. The major cause resulting in seed dormancy comes from the endosperm, the mechanical obstruction of seed coat and fruit shell and the growth inhibitor of seed all could restrained seed germination. The embryo can be germination when the seed ripen. Sulfuric acid scarification, Gibberellins 3 solution soaking seed and 5℃cold stratification treating is most favorable to breaking seed dormancy and improving seed germination, the germination rate is 95%.The endangering cause of T. miqueliana is related to the biological characteristics of this species, but the most reason come from the disturbed of people. The protection strategies contained in situ conservation, strengthen propagation, and so on.