Genetic Diversity Analysis On Wide Litchi (Litchi Chinensis Sonn) Germplasm In China By SSR Marker

China is the origin and domestication centre of cultivated Litchi(Litchi Chinensis Sonn), and once there were abundant wild and cultivated litchi genotypes extensively distributed in southern district of China. But, the living surrounding of wide litchi has been serious narrowed, need to conserve by scientific and effective methods. Up to now, there hasn't report on accession investigation and evaluation of molecular genetic diversity Chinese wild litchi. In the study, total 66 accession samples randomly collected from three kinds of populations each called natural wild litchi forest, semi-wild seedlings and cultivated genotypes was used to get genomic DNA to understand the genetic diversity of the different gene pool by SSR markers. The main results were briefly summarized as follows:1. Twenty-two pairs of SSR primers out of thirty-two were identified have polymorphism bands. Total of 52 alleles have been obtained when use these polymorphic markers to detect the three litchi populations. The average alleles number of polymorphism SSR markers was 2.36, The Nei's average gene diversity(H)was between 0.2960 to 0.3774, and the range of Shannon's genetic diversity index was from 0.4170 to 0.5566 shown that the wild accessions is higher than semi-wild seedlings, and the diversity of cultivars is smaller.2. In the wild litchi accessions, the effective alleles of each locus were 2.36,and the average frequency of the alleles was 1.6618. Average value of The Shannon's Information index was 0.5566. It's indicated that the genetic diversity in the wild litchi population is higher. According to genetic similarity matrix, the UPGAM dendrogram has been drawn by NTNSYS cluster software. Based on genetic distance 0.61, all the accessions can be divided into five groups, WL-18,WL-22 and WL-47 deputy independent groups each with in it, needed to be investigated further more.3. In the semi-wild seedlings accessions,the average alleles of each locus was 2.36, the average frequency of effective alleles was 1.5829. Average value of The Shannon's genetic diversity indexe was 0.5803. It's shown that the genetic diversity in the seedlings population also is larger, but less than in situ wild accessions. The cluster analysis revealed that the accessions sampled from seedlings could be divided into four subgroups based on genetic distance 0.61.4. In the cultivar types, the average alleles of each locus was 2.36,the average frequency of effective alleles was 1.3643. Average value of The Shannon's genetic diversity index was 0.4170.The results indicated that the genetic diversity in litchi cultivars was lower than wild and Semi-wild seedlings litchi populations. UPGAM dendrogram got by cluster analysis implied that 22 cultivars could be divided into 5 groups. It is further testified that molecular fingerprint could supply scientific genetic classification for litchi germplasm.5. Based on genetic similarity coefficient, the UPGAM dendrogram of all accessions from three different populations was made up by NTSYS cluster analysis. The results indicated that the genotypes of wild accessions have a broaden distribution,but the genotypes of semi-wild seedlings and cultivars scattered in some small parts of it. The semi-wild seedlings population is the middle type between wild accession and cultivar of litchi,and had significant genetic differentiation. So,it could play an important role in the course of hybrid breeding and elite varieties selection of litchi. This results gave a clearly outlook of the genetic relationship and genetic diversity level among the three kinds of populations.In the paper, a genomic DNA isolation method－CTAB used in Litchi has been improved in detail and obtained ideal results. Meanwhile,the problems and probably pathways in the molecular genetic diversity analysis and conservation of litchi germplasm have been discussed.