Analysis Of Genetic Diversity Of Quercus Mongolica Based On Phenotype And SSR Molecular Markers

Quercus mongolica is the northernmost cold-tolerant deciduous Quercus in China.It has good ecological use and economic value and is widely used in production and life.And its genetic diversity has always been a research hotspot for breeders.Many studies have proved that there is a certain degree of variation among populations of Q.mongolica,and the results show that the degree of differentiation is different,which is closely related to the sampling range.This study collected 40 provenances of Q.mongolica germplasm resources in 7 provinces in China,and analyzed the genetic diversity of its seedlings.Analysis of the genetic diversity of seedlings from phenotype genetic variation and DNA molecular genetic variation.（1）There were abundant genetic variations in growth traits,photosynthetic parameters,leaf surface traits and leaf anatomical structure of Q.mongolica seedlings（average Shannon Wiener index H’=1.93）.There were significant or extremely significant differences in 26 traits except ground diameter among provenances and within provenances.The average phenotypic differentiation coefficient among provenances was 55.24%,while the genetic variation within provenances was only 44.76%.The variation of dry weight in the middle of the personality was the highest（62.02%）,while the relatively stable genetic character,the leaf moisture content was only 7.36%.There were certain correlations among growth traits,leaf surface type traits,photosynthetic parameters and leaf anatomical structure traits,which could coordinate to adapt to the environment.There was no significant correlation between growth traits and geographical ecological factors of provenance,and there was a certain degree of influence on leaf phenotype,photosynthetic parameters and leaf anatomical characters.（2）Comprehensive evaluation of Q.mongolica provenances.By constructing the principal component score model,the Q.mongolica from different sources was ranked.The main component score ranking shows that the seed sources Ldj,Hgy,Lyf and Jst have higher scores(F_Ldj=12.731,F_Hgy=7.36,F_Lyf=6.116,F_Jst=5.973).They grow better than other provenances.In the fifth category,the growth of Jll and Xly was the worst(F_Jll=-8.577,F_Xly=-9.164),and the principal component score was the lowest.The results of cluster analysis and principal component analysis showed no significant correlation with the distribution of geographical provenances.（3）17 pairs of primers had high polymorphism level（PIC=0.59）,and 13 pairs of primers were derived from EST sequence of Q.mongolica（PIC=0.56）.4 pairs of universal primers from Quercus mongolica（PIC=0.70）.Based on the analysis of SSR loci in EST sequences and chloroplast genome of Q.mongolica in NCBI database,a total of 163 SSR loci were found in132 EST sequences,among which the proportion of dinucleotide AG/CT was the highest.Chloroplast genome contains 88 SSR loci,in which single nucleotide A/T is the most frequent.A total of 63 pairs of EST-SSR primers and 30 pairs of cp SSR were designed,of which 52 pairs could amplify effectively on multiple templates.These primers can provide more marker selection for the genetic diversity of Q.mongolica and Quercus plants.（4）The genetic diversity of Q.mongolica population is rich,and it is relatively high in Quercus.The results of genetic diversity analysis of 40 provenances showed that the average observed heterozygosity Ho=0.557,the average expected heterozygosity He=0.55,and Shannon’s information index I=1.083.The main genetic variation of Q.mongolica was within provenance（93.17%）,and 6.83%of the genetic variation came from between provenances.There is a certain degree of gene flow between provenances（Nm=1.8526）;The habitat isolation among populations was far（affecting the seed and pollen transmission of Q.mongolica）;The biological characteristics of Q.mongolica led to the medium level of genetic differentiation among provenances.Provenance differentiation and mixed population analysis showed that there were three gene flow and migration events among provenances,and the differentiation among provenances was chaotic.The correlation analysis of geographical distance and genetic distance showed that geographical distance had a certain effect on the genetic variation of Q.mongolica provenance population（R²=0.12,p<0.001）.Altitude and longitude have more influence on genetic distance than latitude.These factors formed geographical isolation,and then affected the genetic differentiation level of Q.mongolica.