| Wheat is the largest staple food in the world, increasing its potential yield could never be overstated. Most agronomic traits related to yield are quantitative traits in wheat, searching these quantitative traits loci (QTL) can provide foundations for marker assistant selection and gene clone, and thus improving new high yielding germplasm. Association analysis, which can identify trait-marker or trait-candidate gene relationships based on linkage disequilibrium (LD) in the given population, has been proved to be a powerful approach for studying plant gene (QTL).Analysis of genetic diversity, population structure and kinship were conducted by using 103 winter wheat germplasm by 89 marker loci, in order to clarify population structure and kinship of these assecions which are necessary for further association analysis; Then evaluated marker diversity and linkage disequilibrium (LD) on chromosome 4A. In addition, phenotypes related to yield were characterized for the set of materials. Finally, association test between chromosome 4A polymorphisms with phenotype variation were performed to identify QTLs controled by yield-related traits. The major results are as follows.1. A total of 103 wheat assecions were evaluated for genetic diversity and population structure based on 49 Genomic-SSR and 40 EST-SSR loci. A total of 531 allelic variations were detected with an average allele number of 5.96. The results showed that a total of 531 allelic variations were detected with an average allele number of 5.97. The average PIC (polymorphism information content) and gene diversity values were 0.57 and 0.63, respectively. The results showed that the genetic diversity was relatively high among the assecions used in this study. By NJ cluster and population structure (Bayesian clustering) analysis, the 103 assecions were clustered into 6 main groups Population structure analysis based on mixture model clarified the genetic composition of the 103 assecions, and 68 assecions had a single ancestor relatively, while the other assecions were from mixed ancestors. 2. Marker polymorphisms of chromosome 4A were evaluated using 31 Genomic-SSR (marker density was 2.4cM) in 103 accessions. Totally 208 alleles were identified, the average of alleles per locus was 6.7. The average PIC value and gene diversity were 0.55 and 0.69 relatively. The baseline of LD decay was r~2=0.054 and LD extended～3cM in chromosome 4A. It was suitable to use genome scan association analysis approach. Three LD blocks were found, one is near the centromere and the other two were in the long arm of chromosome 4A.3. Marker-trait association analysis was calculated by mixed linear model in software TASSEL V2.01. Ten SSR loci were detected significant associated with agronomic traits. In which, one SSR loci are associated with Plant height and Spikelets per spike relatively, two SSR loci are associated with Thousand-kernel weight, four SSR loci are associated with Spike length and Spikelets density relatively, Six SSR loci are associated with Grains per spike. Among them, some QTLs were also reported in previous studies. The results enhance previous QTL information and provide additional QTL information for marker-assisted selection and gene clone.
|
PDF Full Text Request