Association Analysis Of Important Traits Based On SSR Markers In Cunninghamia Lanceolata

Chinese fir [(Cunninghamia lanceolata(Lamb.)Hook.] is a unique and excellent fast-growing timber species,distributed throughout 17 provinces and autonomous regions in southern China.188 C.lanceolata clones from 11 geographical provenances such as Rongshui Guangxi,Jingxian Hunan and Jinping Guizhou were used as materials in the research.Wood cellulose and lignin content were determined to analyze the variation pattern between provenances and clones.Genetic diversity and population structure of Chinese fir population were analyzed by a set of markers developed from genes associated with wood formation,combined with self-developed EST-SSR markers.SSR loci associated with phenotypic traits were found through association analysis,and its elite alleles were explored.The main results are as follows:(1)Prediction model of Chinese fir cellulose and lignin content were established by Van Soest method combined with near infrared spectrum,the correlation coefficient reached 0.9409 and 0.9468 respectively,which indicated the model had good prediction effect,and could be used to predict actual value.Analysis on variation pattern of wood cellulose and lignin content showed that,they both had lower variation coefficient which was 6.00% and 5.89% respectively.Variance analysis indicated that there was extremely significant difference on cellulose content among different clones.(2)The full length of 10 genes associated with Chinese firbiosynthesis was cloned,which takes up 32785 bp of C.lanceolata genome.13 SSR loci were found and 7 polymorphic SSR markers were developed,a total of 17 allelic variations were detected with an average allele number of 2.429,polymorphism primers occupied 53.8% of the total primers designed.(3)40 pairs of polymorphic EST-SSR primers were developed independently based on EST sequences acquired from transcriptome sequencing,accounts for 16.67% of the total designed primers.A total of 338 allelic variations were detected with an average allele number of 4.11.The main allele frequency,Shannon's index and polymorphism information content were 0.7173,0.6888 and 0.3358 respectively.The results showed that the genetic diversity of materials was relatively abundant.Analysis of population structure indicated that the Chinese fir population could be divided into two subgroups.The average D' value of SSR loci combinations in the population was 0.332,linkage disequilibrium existed in 165 SSR loci combinations when P<0.01.(4)11 loci associated with traits were detected through association analysis based on population structure,4 loci associated with crystallinity,2 loci associated with lignin content,and 5 loci associated with branch diameter,cellulose content,DBH,blade aspect ratio and sapwood and heartwood ratio respectively.There were difference among the average alleles of positive and negative effects on loci;the allele variation of loci had their own phenotypic directions and sizes among different traits;a number of excellent associated loci,allele variation and carrier materials of association excellent loci were explored.