| Ammopiptanthus mongolicus is a perennial plant of the genus Ammopiptanthus,which is endemic in China.It is also a floristic plant in Alashan desert area.Tetraena mongolica Maxim belongs to Zygophyllaceae and is a unique relic plant in China.In this study,the wild genetic resources of Ammopiptanthus mongolicus and Tetraena mongolica Maxim were collected.Genetic diversities,genetic structures and genetic variations of these plant populations were analyzed by DNA sequencing,SSR and ISSR molecular markers.As a result,some suggestions on species protection and sustainable utilization of Ammopiptanthus mongolicus and Tetraena mongolica Maxim were put forward.The main results are as follows:(1)The cpDNA of nine wild populations of Ammopiptanthus mongolicus was sequenced using the non-coding chloroplast fragment psbC-trnS.The total length of the sequence was 1493-1545 bp,with a total of 103 mutation sites.Twelve haplotypes were identified according to the sequence variation loci,of which H2 haplotype was the most widely distributed,presumably the ancestral haplotype.Haploid diversity(Hd)index was 0.29748 at species level,nucleotide diversity(?)index was 0.00166,and Hd index ranged from 0 to 0.81319 at population level.The total genetic diversity(Ht)was 0.309(0.0903)higher than that of the inter-population genetic diversity(Hs)was 0.293(0.0784),and most of the gene exchange was within the population.The genetic differentiation coefficient NST=0.018 was less than GST=0.053(p>0.05,not significant),indicating that there was no obvious pedigree geographical structure in the population.The results of neutrality test showed that the population of Ammopiptanthus mongolica in Western Inner Mongolia refused to evolve neutrally and experienced expansion or negative selection of gene loci.(2)The genetic diversity of 9 populations of Ammopiptanthus mongolicus was studied based on ISSR molecular markers.A total of 83 bands were detected by 10 ISSR primers,with 6-11 primers per primer,averaging 8.3;the population average polymorphic locus percentage(PPB)is 46.85%;Nei's genetic diversity index(H)is 0.1643,Shannon information index(I)is 0.2449,The level of genetic diversity in Ammopiptanthus mongolicus was low;the coefficient of genetic differentiation(Gst)was 0.3118,accounting for 31.18%of the genetic differentiation among species,while 68.82%of the remaining genetic differentiation occurred within the populations;the gene flow Nm is 1.1034,indicating that high gene exchanges among populations;cluster analysis showed that 9 populations of Ammopiptanthus mongolicus could be divided into three groups.(3)The genetic diversity of 6 populations of Tetraena mongolica Maxim was studied based on SSR molecular markers.13 SSR primers amplified showed that the genetic diversity level of Tetraena mongolica Maxim was high,the average allele richness(AR)is 9.7,the average Shannon index(I)is 1.864,the population heterozygote was high,and the average Fst was 0.055,the mean consistency is 0.7495,which indicates that there is little genetic differentiation among the populations in the study area;the average gene flow among the populations is 5.171,and there is a wide range of gene flow;Structure,UPGMA and PCoA analysis show that the genetic differentiation of populations is not obvious and clustering is not obvious;Hardy Weinberg test of 13 loci shows that there is imbalance in half of the populations,and there is a possible risk of inbreeding recession.(4)The genetic parameters of Ammopiptanthus mongolicus are correlated with altitude(0.436),but not with other geographical factors;the genetic parameters of Tetraena mongolica Maxim has strong correlation with temperature(-0.267)and precipitation(0.368),weak correlation with wind speed(-0.021),so temperature and precipitation may be a strong driving factor for the formation of genetic structure of Tetraena mongolica Maxim;It shows a certain correlation(0.454)between genetic distance and geographical distance.(5)According to the results of genetic diversity analysis,DNA sequencing and microsatellite markers are both suitable for genetic diversity research.Sequencing technology can excavate genetic mutations of single or multiple bases at the nucleotide level,thus playing an important role in genetic variation analysis and pedigree geography analysis.Microsatellite molecular marker technology,based on sequence length changes,is still a classical method for establishing genetic map and genetic structure analysis of species.Based on the above results,some suggestions for the conservation and sustainable utilization of Ammopiptanthus mongolica and Tetraena mongolica Maxim were put forward in this study.For the wild genetic resources of Ammopiptanthus mongolica,besides adopting in-situ conservation strategy to ensure the genetic diversity of its original population,we should focus on introducing and breeding Ammopiptanthus mongolica germplasm resources in different regions to ensure gene flow.In view of the wild genetic resources of Tetraena mongolica Maxim,in-situ conservation strategy was adopted to ensure the genetic diversity of its original population,and ex-situ conservation could be carried out combinatied with environmental factors. |
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