Genetic Diversity Evaluation And Core Breeding Population Construction Of Pinus Tabuliformis Seed Orchard In Wanjiagou

Pinus tabuliformis,a perennial evergreen tree characteristically in China,is widely distributed and highly adaptable,which is an important tree species for afforestation and soil conservation in northern region.The genetic diversity of P.tabuliformis clones（parents）and half-sib progenies were evaluated by EST-SSR molecular marker technique,taking the P.tabuliformis breeding population as our research object in Wanjiagou National Breeding Base in Tumotezuo Banner,Hohhot,Inner Mongolia.The core breeding populations and their fingerprints of P.tabuliformis seed orchard were constructed.The paternal parent of the half-sib offspring was preliminarily identified.It provides a theoretical basis for the study of genetic breeding of P.tabuliformis seed orchard.The main results are as follows:（1）A total of 2811 EST-SSR loci were mined from the transcriptome of cotyledons（including shoot tips）of half-sib progeny seedlings in P.tabuliformis seed orchard.A total of 22 pairs of highly polymorphic primers were screened from newly developed and published EST-SSR primers of P.tabuliformis and its related species for genetic analysis of breeding populations in Wanjiagou P.tabuliformis seed orchard.（2）Twenty-two polymorphic EST-SSR primers were used to analyze the genetic diversity of 203 clones（parents）in P.tabuliformis seed orchard.The mean value of Na,PIC was 5.83 and 0.6 respectively.The EST-SSR primers used in this study can effectively determine the genetic information of breeding population of P.tabuliformis seed orchard in Wangjiagou.The mean value of F_STwas 0.014,and the genetic differentiation among populations was weak.AMOVA results showed that 99%of the genetic variation came from individuals within the P.tabuliformis clone population.And P.tabuliformis clone（parents）population were divided the into 7 subgroups by Structure analysis,which was consistent with the results of PCo A analysis,indicating that the P.tabuliformis clones from Ningcheng,Qinyuan,Weichang and Pingquan provenance areas did not show clear geographical distribution characteristics.（3）A core breeding population containing 50 samples was constructed under the condition of maximum allele number by using simulated annealing algorithm of Powermarker software.The sampling ratio was 24.3%.The genetic parameters such as Na,Ne and PIC values of the core breeding germplasm and the original breeding germplasm were tested by T test,and no significant difference was found.It was determined that level of genetic variation of the original germplasm can represented by the core germplasm as much as possible.The fingerprints of the core breeding population were made in P.tabuliformis seed orchard after the genotype coding assignment of 22 EST-SSR loci.（4）22 pairs of polymorphic EST-SSR primers were used to analyze the genetic diversity of 336 half-sib progeny from 21 families of P.tabuliformis seed orchards in Wangjiagou.It was found that 25%of genetic differentiation among the half-sib progeny families of P.tabuliformis seed orchards,and the genetic variation among different individuals in the family was 75%.The population genetic structure analysis divided the progeny into two subgroups.（5）The Cervus software（confidence level 95%）was used to preliminarily identify the male parent of 73 offspring in 336 half-sib progeny of P.tabuliformis,and the identification rate was 21.73%.