Genetic Diversity Analysis And Molecular ID Card Construction Of Ancient Chestnut Trees And Varieties (Lines) In Yanshan

Yanshan region is a ancient producing area of Castanea mollissima BL in China.They contain abundant variation types of Chinese Chestnut and are good sources of genetic research and innovation for improvement of Chinese Chestnut.In this study,20 pairs of SSR fluorescent molecular markers were used to study the genetic diversity,genetic relationships,population genetic structure and construct Molecular ID cards of 69 ancient chestnut trees and 93 varieties（lines）in Yanshan to provide theoretical reference for germplasm conservation,breeding material selection and germplasm identification.The test results show that:1.A total of 109 alleles were detected in 69 ancient trees by 20 pairs of primers,and the number of alleles（Na）amplified by each pair of primers ranged from 2 to 13,with an average of 5.450.The polymorphism information content（PIC）,Shannon information index（I）and expected heterozygosity（He）ranged from 0.055 to 0.742,0.043 to 1.695 and 0.014 to 0.779,with the mean values of 0.460,0.998 and 0.520,respectively.The average observed heterozygosity of populations（Ho=0.463）was higher than the expected heterozygosity（He=0.427）,the mean Fixation index（F）was-0.089,and the mean Nei’s diversity index（H）was 0.512,indicating that the genetic diversity of ancient chestnut tree in Yanshan was relatively high.The mean value of gene flow（N_m）was 2.006,which limited genetic differentiation among populations to a certain extent.The average genetic differentiation coefficient(F_st)was 0.129,indicating the medium differentiation level.Molecular analysis of variance（AMOVA）showed that genetic variation within populations（95%）was higher than that between populations（5%）.The Unweighted Pair-Group Method with Arithmetic means（UPGMA）was used to draw the individual and population cluster maps,and the results showed that the distance between counties（districts）was consistent on the whole.And there is no obvious correlation with geographical distribution.Population Structure analysis showed that there was gene introgression among counties,which might be related to higher gene flow.2.A total of 114 alleles were detected in 93 chestnut varieties（lines）,with an average of 5.700 alleles.Polymorphism information content（PIC）,Shannon information index（Ⅰ）and expected heterozygosity（He）ranged from 0.097 to 0.729,0.209 to 1.879 and 0.102 to 0.762,with the mean values of 0.482,1.026 and 0.532,respectively.The mean observed heterozygosity（Ho=0.511）was higher than the expected heterozygosity（He=0.476）,the mean fixed index（F）was-0.087,and the mean Nei’s diversity index（H）was 0.533,indicating that Yanshan chestnut varieties（lines）had relatively high genetic diversity.The mean value of gene flow（N_m）was 2.179,which limited genetic differentiation to a certain extent.The average genetic differentiation coefficient(F_st)was 0.103,indicating a medium differentiation level.AMOVA analysis showed that intra-population genetic variation（96%）was higher than inter-population genetic variation（4%）.The phylogenetic tree and genetic consistency and genetic distance analysis showed that the phylogenetic relationships between populations were correlated with geographical distribution.The results showed that the genetic Structure of each population was complex,and that Changli,Huairou and Qinglong had different gene groups than other populations.3.Screening core primers to construct molecular ID cards.From 20 pairs of primers,5 and 7 pairs of core primers were selected,which could completely distinguish chestnut ancient trees and varieties（lines）.Based on the analysis and coding of the core primers,69 and 93 molecular ID cards of chestnut germplasm were constructed,respectively.In conclusion,the Chestnut germplasm in Yanshan selected in this study has higher genetic diversity and better ability to adapt to habitat changes.The individual heterozygosity of tested ancient trees and varieties（lines）was high,the genetic differentiation between populations was moderate,and there was a certain degree of gene flow.The experimental germplasm can provide a material source for the creation of new germplasm,and the DNA molecular ID cards constructed by the core primers can provide help for the concise and efficient identification of germplasm.The individual heterozygosity of tested ancient trees and varieties（lines）was high,the genetic differentiation between populations was moderate,and there was a certain degree of gene flow.The experimental germplasm can provide a material source for the creation of new germplasm,and the DNA molecular ID card constructed by the core primers can provide help for the identification of germplasm concisely and efficiently.