Genetic Structure And Variation Of Chestnut Blight Resistance For Half-sib Offsprings In Castanea Henryi

Castanea henryi is an important woody grain tree species in south China.With the continuous expansion of C.henryi industry and planting area,it is particularly important to breed varieties.Due to the weak genetic basis on chestnut blight resistance,no high resistance and excellent varieties have been bred for application.In this study,the EST-SSR markers developed were used to analyze the genetic diversity and genetic structure of the half-sibling offspring population.The variation of chestnut blight resistance and seedling traits were analyzed,and the excellent families and individuals were selected.It can provide reference for further breeding.The main results are as follows:1.Using 6 C.henryi,3 C.mollissima and 3 C.crenata as materials,108 primers of EST-SSR were designed and synthesized for amplification,and 12 pairs of EST-SSR primers with good stability,high repeatability and high polymorphism were selected.The polymorphic percentage of primersFAFUZLEST-7,FAFUZLEST-9,FAFUZLEST-11,FAFUZLEST-12,and FAFUZLEST-18 were all 100%.2.Genetic diversity and genetic structure of 14 half-siboffspring populations were analyzed by using 18 pairs of EST-SSR primers.The range of Shanon information index(I)was 1.037?1.287,the average effective allele number Ne=3.015,the average observed heterozygosity Ho=0.584,the average expected heterozygosity He=0.614,the gene differentiation coefficient Fst=0.1253,and the gene flow N_m=1.7458.The results of AMOVA analysis showed that only 10%of the inter-family variation was found,and most of the variation came from within the family.These results indicated that there is a rich genetic diversity in the half-sibling population,a moderate degree of genetic differentiation and a large degree of gene exchange.The genetic variation is mainly from within the family.The 14 half-sib families were divided into 2 classes.3.The genetic analysis of chestnut blight resistance and seedling traits in 14 half-sib families showed that the average coefficient of variation(CV)of each trait was 29.97%,indicating that inter-family variation was abundant.The average CV of each family was sorted and the top three families were DJZ,XJZ and HZZ.In addition,the two traits with the highest correlation coefficients were leaf length and leaf area(R=0.931)and leaf width and leaf area(R=0.938),respectively.The cluster analysis of 12 phenotypic traits was carried out,and the 14half-sib families were divided into 3 categories.The excellent families and individuals were selected.The five families with the stronger disease resistance were:WKCM,YTZ,XJZ,HZ and TZ.The 5 families with the excellent growth traits were SFZ,XJZ,NJZ(zs),YTZ and HZ.The families YTZ,XJZ and HZ showed good disease resistance and growth.The 7 individuals with strong disease resistance and good growth condition were selected as 8-10,2-23,7-26,11-29,14-31,12-29 and 2-19,respectively.The 7 excellent individuals were selected for paternal identification,and the male parent of 2-19 was identified as CSH,the male parent of 2-23 was identified as WKCM,the male parent of 7-26was identified as TZ,the male parent of 8-10 was identified as CSH,the male parent of 11-29 was identified as YZ,the male parent of 12-29 was identified as ZJZ,and the male parent of 14-31 was identified as NJZ(ws).4.Eighteen pairs of EST-SSR markers were used to correlate the phenotypic traits of C.henryi.The general linear model(GLM)concluded that there was a significant correlation between 15 loci and 10 phenotypic traits,and the mixed linear model(MLM)concluded that there was a significant correlation between 10 loci and 11 phenotypic traits.The variation contribution rate between FAFUZLEST-15 and the incidence of infection was 95.53%.