Genetic Diversity Analysis Of Sesame And Association Analysis Of Yield And Quality Traits

Sesame (Sesamum indicum L.), which belongs to Sesamum genus in Pedaliaceae family, is one of the important oil crops in China. Along with the developing application of molecular markers, genetic diversity analysis of germplasm resources and DNA fingerprint construction of sesame cultivars have been carried out in recent years. In this study, we used42pairs of polymorphic SSR markers to analyze the genetic diversity and population structure of545sesame genetic resources collected worldwidely from China and other countries and revealed their genetic relationship between domestic and foreign sesame resources. We also investigated the genetic diversity of main cultivars in China. Based on the above results, we choose371materials as core germplasm resource from the above resource pool and analyzed the correlation relationship between phenotypic data and markers on development stage length, yield and quality traits. Results of linkage sites identification and excellent allele mutation discovery gave the theoretical and technical foundation for improving sesame breeding efficiency.1. Genetic diversity and population structure of545sesame germplasm resources collected from China and foreign countries were analyzed with42pairs of polymorphic SSR markers, which were selected from1126SSR primers. A total of106alleles were detected among545sesame accessions. The numbers of detected alleles varied from3to9with an average of3.8095alleles per locus. The average of polymorphism information content (PIC) values was0.4092. Results of UPGMA cluster, two-dimension correspondence analysis and population structure analysis were consistent and revealed that545sesame germplasm is divided into3groups. Genetic differentiation of worldwide sesame resources is small and their genetic relationship is relative close; however, foreign resources are more diverse than Chinese domestic accessions. Genetic diversity of domestic resources does not completely correlate with geographical distribution. However, the genetic relationship between the materials from Northeast and North of China and main production area, such as Henan were relatively further. Therefore, to broaden the genetic base of sesame, strengthening the utilization of foreign resources and ignoring the restriction of geographic distance among domestic resources are encouraged in sesame breeding.2. We analyzed the genetic diversity of112sesame cultivars of China selected since1949with42polymorphic SSR markers. A total of135alleles were detected, and numbers of detected alleles varied from2to9with an average of3.2143alleles per locus. The average of PIC values was0.4092. Similarity coefficients ranged from0.4421～0.9900. Clustering results indicated that112varieties are divided into4groups and their genetic basis was narrow, accompanied deficient diversity. Frequent utilization of similar parents is avoided to expand the genetic basis of sesame.3. We studied the genetic diversity and association analysis of yield and quality traits of371sesame genetic resources from China and other countries in the word using42pairs polymorphic SSR markers. These materials were divided into two groups. Correlation analysis were detected using TASSEL GLM (gengral linear model) and MLM (mixed linear model). Different degrees of LD were found among nonsyntenic SSR sites, which suggested that there had been historical recombination among linkage groups. Numbers of loci pairs supporting LD with P=0.01accounted for38%.11SSR loci were detected and associated with10agronomic traits. Moreover, some loci associated with two or more traits at the same time, which might be result from the genetic basis of correlating traits as well as pleiotropic effects of a specific gene. Some traits were associated with multiple loci. Detection of the elite alleles of the agronomic traits provided theoretical basis on molecular design breeding in sesame.