Study On Genetic Diversity And Genetic Structure Of Populus Talassica Kom. Population In Xinjiang

Populus talassica is a Populus tree species and deciduous tree of Salicaceae.It is an important species in the natural secondary forest ecosystem of the Tianshan Valley in Xinjiang Uygur Autonomous Region.It has important materials and ecological value.Based on the survey of the distribution of the resources of the Populus talassica in Xinjiang,this study used six population samples distributed in the mountain valleys of the central and western Tianshan Mountains in Xinjiang as materials,using SSR molecular markers to different population groups,different age groups,male and female groups of the genetic diversity and population genetic structure of parental and child populations were studied in order to provide theoretical basis for the protection of the germplasm resources of Populus talassica and the development of breeding population strategies.The main findings were as follows:?1?23 primers were screened from 480 pairs of SSR primers.neutral detection of 316 individuals from the population of Populus talassica was carried out using 23 pairs of primers.The results showed that 23 pairs of primers were in the 95%confidence interval,indicating that most of the SSR primers used were neutral markers,which were basically unaffected by external selection factors.In population genetics analysis,from the distribution of related sites in the population,multiple sites were in the Hardy-Weinberg imbalance,indicating that the population of Populus talassica was affected by evolutionary selection factors.?2?Using 23 primers to analyze the 6 populations of Populus talassica,the results showed that the average heterozygosity?Ho?was 0.507,the average heterozygosity?He?was 0.641,and the Nei' gene diversity index was 0.346?GCPM₂364?.Between-1.1236?GCPM₆72?,the genetic diversity of different populations of Populus talassica was at a high level;the genetic diversity among the six populations of Populus talassica was different,and the genetic diversity of Kemen?KM?was the highest.The Kuche?KC?was the lowest;the average fixed index?F?values of the six populations were 0.120,0.181,0.116,0.110,0.130,and 0.163,respectively.Only 6 loci?Fis<0?indicated that the heterozygous deletion of the Populus talassica population The expression of inbreeding population;the population genetic differentiation coefficient?Fst?mean value was 0.094,indicating that the degree of genetic differentiation among populations of Populus talassica was low,and the difference mainly comes from within individuals within the group.The reason may be due to the high level between groups.The gene communication;MANTAL and AMOVA tests showed that the genetic distance of the population was positively correlated with its geographical distance,89.79%of the genetic variation existed among the individuals within the population,and 10.21%of the genetic variation existed intergroup;where in upstream?SY?and downstream?XY?of the highest similarity.The intrinsic factor of the large gene flow of Populus talassica may be due to the large number of male flowers and the large amount of pollen,as well as the spread of seeds with wind and water.?3?The Shannon's index and Nei'index of each age group of populus Populus talassica were the highest among the three age groups in terms of the genetic diversity index of 10-30a,but the overall trend did not change much in 100 years,showing a basically stable development trend.The degree of differentiation among age groups was low?Gst=0.015?.Among them,the genetic similarity of 31-60a and above 60a age groups was the highest?0.939?,while the transmission distance was the smallest?0.011?.The lowest genetic similarity was 0.896 at ages 10-30a and above 60a,and the highest genetic distance was 0.067.The average differentiation coefficient?Gst?was only 0.015.The percentage of intra-age genetic variation was 98 percent,and the percentage of inter-age genetic variation was only 2 percent.The reasons for the small genetic difference among the three adjacent age groups may be:there was a certain degree of kinship among individuals of different age groups;The sampling area was the core distribution area of populus Populus talassica,and there was certain gene exchange among different age groups.The sample collection area was relatively less affected by human activities.?4?The number of effective alleles?Na?,number of polymorphic loci?Np?,expected heterozygosity?He?and private alleles of female subpopulations were higher than that of male subpopulations in Populus talassica.The observed heterozygosity?Ho?of both male and female subpopulations was lower than that of expected heterozygosity?He?,and the number of inbreeding lines?Fis?was positive,indicating the absence of heterozygote between male and female populations in populus densiflora.According to the principle of maximum likelihood value,the six natural populations of populus densifolia were divided into three theoretical groups,each containing two subpopulations.In addition,there was no significant relationship between the genetic structure and gender between male and female subpopulations in Populus talassica,and the difference between male and female populations was smaller than that between different geographical locations.The genetic diversity of male and female population in the lower reaches was significantly higher than that in the middle and upper reaches,which might be because the seeds of populus densiflora in the upper reaches could flow with the water,resulting in a higher level of gene flow in the population.Both male and female subpopulation mobility?M?of the same population were greater than 0.8,indicating a high level of gene exchange.?5?At the population level,the genetic diversity of the half-sibling family and the sampling population of Populus talassica was higher?Na=10.26,Ne=4.4498,I=1.511,Ho=0.5208,He=0.6822?,and the parameters of the population diversity of the offspring were lower than that of the parent population except the expected heterozygosity.Molecular variance analysis?AMOVA?showed that the variation was concentrated among individuals within the population?78.53%?,and the variation in the semi-sibling family group was significantly less than that in the parental group.The paternal origin of the offspring group is limited by geographical location;The differences in the genetic distance between parents were compared among the three Populus talassica semi-sibling groups,with the diversity value of 1.029,the highest value of NLK?1.089?,and the lowest value of KM?0.988?.The reasons were related to the number of fathers in the offspring group and the genetic distance between parents.?6?The conservation and utilization strategies of Populus talassica,germplasm resources were proposed.Firstly,the natural population of Populus talassica,distributed in kashi river valley in yili region of xinjiang is protected by the method of local conservation,so as to provide the most complete basic population guarantee for the implementation of the long-term genetic improvement plan of populus densifolia.At the same time,remote protection should also be taken into consideration.Specifically,gene resource collection combining optimal tree selection can be carried out around the population of Populus talassica,in xinjiang.Based on this,core germplasm can be constructed by using SSR molecular markers to maximize the protection of Populus talassica,gene resources.Furthermore,the germplasm resources of Populus talassica can be protected and utilized in different places through the germplasm collection nursery of superior trees,the germplasm preservation nursery of core germplasm with different target characters,and the comparative test forest of superior clones.In addition,it can also be considered to take the natural forest of dense Populus talassica,in the kashi river basin as the core to select fine single plant of male and female to be transported to the appropriate area for afforestation,and to expand the population distribution and area by means of species regeneration and natural hybridization,so as to realize the purpose of ex situ conservation from the level of cultivation and utilization.