Study On Genetic Structure Of Aquilaria In China

There are two genus of Aquilaria in China, including A. sinensis(Lour.) Sprengel and A. yunnanensis S. C. Huang. However, due to human activities and the damage of environment, they are threatened to be extincted. And few of its genetic structure and geographic affinity are studied. In this study, 1 reference population(A. crassna) and 10 populations of Aquilaria in China were analsyed, aims to better understand the history of their genealogy, the genetic structure and the formation of their genetic pattern. Also it proposed the corresponding protection and development policy based on its genetic structure. The main results are as follows:1. Phylogegraphy of AquilariaITS and cp DNA sequences were analysised to reveal the evolutionary history of Aquilaria in China. Two cpDNA intergenic spacer( trnvX2-ndhC and psbB-psbH) are selected from 21 pairs of primers which were used for our study. After sequence alignment the length of trnvX2-ndhC were 556 bp, the G + C content were 25.4%. Total of nine haplotypes were recovered(Haplotypes diversity=0.709, nucleotide diversity = 0.01494). After sequence alignment the length of psbB-psbH were 610 bp, the content of G+C were 33.3%, resulting in three haplotypes, Hd was 0.492, ? was 0.00243. The length of ITS region was 681 bp, ITS1 length was 246 bp, 5.8s long 163 bp, ITS2 length 271 bp. The G + C content were 55.3%, ITS1 had 4 mutation sites, 5.8s and ITS2 had no mutation sites. Combined the 20 Genbank sequrnces, 34 mutation sites were obtained. ITS1 had 19 mutation sites. There were three mutation sites in 5.8s. ITS2 had 12 mutation sites. ITS sequences generated 13 haplotypes( Hd=0.86, ?=0.0107). After population dynamics inspection and combined ITS data, we found that 10 populations of Aquilaria in China has experienced rapid expansion event in recent historical period. Haplotype data showed that Guangdong and Guangxi provinces have the most widespread type and quantity haplotypes, suggesting that there may be a distribution or origin centers of Aquilaria in China, and Yunnan, Hainan and Fujian haplotypes were derived haplotype.2. SSR analysisGenetic structure and lineage were analysed using SSR markers. 20 novel polymorphic SSR markers have been choiced among 121 SSR markers which were developed and characterized. The accessions displayed 266 alleles, the mean number of alleles(k) were 13.3, and the mean observed heterozygosity(Ho) was 0.826, the average expected heterozygosity(He)were 0.787. All loci were highly polymorphic loci(PIC> 0.5) there was no linkage between the phenomenon and the site. However, the null frequency of SSR1-28 is high(p>0.2), so its not suitable to evaluate the population diversity. Only 19 SSR markers were employed to evaluate population diversity. The results showed that the average number of alleles(Na) were 5.277, Ho and He were 0.841 and 0.657, the number of Fixation Indices are negative(Fis <0). Hardy-Weinberg equilibrium test indicated 4 of 11 population deviation from equilibrium.Principal coordinates analysis(PCoA), Structure and UPGMA cluster analysis showed that 11 populations were clustered into 3 major groups. A. crassna was alone as a lineage, whose genes from a single gene pool. Aquilaria in China can be divided into two lineages coming from different gene pool. The gene flow was low between different lineages(Nm =1.09). The gene flow was high in lineage(Lineages1, Nm=2.27; Lineages2, Nm=5.06). This may be related with the geographical factors. At the junction of two lineages there were many mountains, which hinder the expansion of exchanges and lineage genes between species. AMOVA indicated that 7.03% variance was attributable to among-populations diversity and the rest(81.39%) to differences within populations. The mean coefficient of gene differentiation(Fst) was 0.1862. Bottleneck inspection found that in addition ASH populations all populations were not experienced bottleneck. IBD test revealed that genetic distance and geographic distances has no relevant.3. Protection StrategyGuangdong and Guangxi provinces should be protected as a hotspot and more numbers of individuals should be protected. A. yunnanensis and ASF populations also should be protected due to their unique haplotypes.