Diversity comparison and phylogenetic relationships of cocksfoot (Dactylis glomerata L.) germplasm as revealed by SSR markers

Abstract

Phylogenetic relationships among and within 16 accessions collected from China, Russia, Kazakhstan, India and Japan were investigated using SSR markers. The 21 SSR primer pairs generated a total of 143 polymorphicalleles, with an average of 6.8 alleles per locus, and a range of 3-13 alleles. The average geneticdiversity, as measured by the polymorphic information content (PIC), was 0.33. The average polymorphic rate (P) for this species was 90.7%, suggesting a high degree of genetic diversity. Analysis of molecular variation (AMOVA) revealed larger genetic variation within accessions (65.75%) and geographical regions (75.58%) rather than between them, while among ploidy level variance contributed only 2.62%. A high degree of geneticdiversity within tetraploid group was detected based on the polymorphicrate (P=94.23%) and shannon's information index of diversity (I=0.4300) when compared with diploid group (P=91.25%, I=0.3922). The values of the genetic identity (GI) among accessions ranged from 0.7320 to 0.9691 and were used to produce a dendrogram using the UPGMA approach. The 16 accessions were grouped into two major clusters (GI=0.876); specifically, all tetraploid (2n=4x=28) accessions originating from different regions were grouped into the same cluster, whereas the diploid (2n=2x=14) accessions were grouped into the two major clusters. The dendrogram was concordant with the morphological variability, agronomic traits and karyotype. Generally, the results of this study indicate that cocksfoot germplasm contains high molecular variation within accession and geographical region. The implications of these results for conservation of the species were discussed.