Genetic Diversity and Population Structure in Perennial Ryegrass Germplasm Assessed by Simple Sequence Repeat (SSR) Markers.

The objective of this study was to evaluate genetic diversity and population structure in perennial ryegrass germplasm. One hundred and ninety two perennial ryegrass (Lolium perenne L.) accessions from 43 countries worldwide were screened with 114 Simple Sequence Repeat (SSR) markers. Genomic DNA was extracted from young leaf tissues. SSR fragments were separated in an automatic ABI 3730 DNA Sequencer that uses fluorescently labeled dyes for detection of DNA. The results from cluster analysis by unweighted pair-group methods using arithmetic averages (UPGMA) and principal component analysis (PCA) showed that the perennial ryegrass collection was diverse. The first three principle components only explained 12.5 % (7.7 %, 2.6 %, and 2.2%) of the total variation. Several commercial cultivars clustered together, suggesting that genetic diversity in commercial cultivars is limited. The STRUCTURE analysis indicated that these perennial ryegrass materials could be divided into 5 subgroups. Analysis of genetic diversity and population structure in perennial ryegrass germplasm provides important information for better using germplasm resources in gene identification and cultivar improvement.