Genetic Diversity Research And Association Mapping Of Three Agronomic Traits In Synthetic Hexaploid Wheat

The creation of Synthetic hexaploid wheat provides conditions for the utilization of wheat-related species on the excellent resources, genetic diversity and elite genes. Association mapping (AM) is a new way to identify the association between the target traits and genetic markers based on linkage disequilibrium (LD) that is a supplementary of QTL. In this study, 110 wheat accessions consisted of 86 SHW germplasms and 24 conventional wheat varieties were evaluated for 3 yield-related traits in two years at Yangling. Genetic diversity, population structure, UPGMA and linkage disequilibrium analysis wan conducted based on 201 SSR markers across the 21 chromosomes in wheat. Association mapping between molecular markers and phenotypic traits was analyzed with the consideration of population structure (Q). The major results were as follows:1. Three agronomic traits, thousand kernels weight (TKW), grains per spike (GPS) and spike length (SL) were estimated in 2014 and 2015 at Yangling. Statistical analysis showed that the highest coefficient of variation was the GPS in the synthetic hexaploid wheat. The difference of three traits of the SHW showed a very significant level. It indicated that synthetic hexaploid wheat with abundant phenotypic diversity for association mapping.2. Genotype analysis was performed on 110 Wheat Cultivars with 201 polymorphic SSR markers.1323 alleles were detected with an average of 6.57 per locus. The genetic diversity with a mean value of 0.755. Polymorphic information content (PIC) of each primer with the average level of 0.719. Number of alleles and average genetic richness showed on genome D>B>A, genetic diversity and PIC displayed on genome B>D>A. Genetic diversity and PIC positively correlated with allele number. It revealed that the D genome provided by the CIMMYT has high genetic diversity and rich genetic variation.3.110 accessions were assigned to three subgroups (SG) based on delta K (AK). The clusters by UPGMA based on Nei’s1973 mostly agreed with STRUCTURE analysis results. It indicated that genetic background of most synthetic hexaploid wheat germplasms varied greatly comparing with conventional varieties while some materials may produce gene exchange or influenced by environmental factors.4. A total of 20101 locus pairs were calculated based on 210 SSR markers and among them, 610 linked locus pairs were detected (P<0.01). The critical value of r2 was 0.9303 based on the distribution of 95% unlinked r2. LD decay curve showed the LD extends about 9.85 cM in whole genome of synthetic hexaploid wheat. The linkage disequilibrium analysis in this experiment can be a reference for the next association analysis.5.21 significant markers (P<0.05) were detected both in 2014 and 2015. The molecular markers associated with phenotypic would provide reference for the selection of hybrid combination, discovery of alleles and the molecular marker assisted breeding.