Genetic diversity patterns within and among varieties of Korean orchardgrass (Dactylis glomerata L.) based on SSR and EST-SSR analysis

The development of orchardgrass (Dactylis glomerata L.) varieties began in the 1970s, and varieties with tolerance to summer depression have been developed in Korea. However, the patterns of genetic diversity have not yet been well characterized. In this study, 60 simple sequence repeat (SSR) markers were shown to generate a total of 607 alleles from five Korean and two non-Korean varieties. The number of alleles ranged from 3 to 27, averaging 10.1 per locus. The polymorphism informative content (PIC) values ranged from 0.127 to 0.919, with an average of 0.585, in 84 individuals (12 individuals each from seven varieties). The average within-variety genetic distance was lowest in the ‘Onnuri’ variety at 0.536 (0.414–0.646) and was highest in ‘Onnuri 2ho’ at 0.582 (0.399–0.738). The lowest average between-variety genetic distance, 0.572 (0.418–0.741), was found between ‘Onnuri’ and ‘LuckyOne 2ho’, and the highest, 0.656 (0.514–0.795), was found between ‘Onnuri 2ho’ and ‘Potomac’. Six different clusters (clusters I–VI) were identified by using the unweighted pair group method with the arithmetic mean (UPGMA), and clusters II–VI contained only Korean varieties. An analysis of the molecular variation based on our SSR marker systems confirmed that most of the molecular diversity was due to differences within (92%) rather than among (8%) varieties. Using bulked data, UPGMA phylogenetic and 3D principal component analyses based on genetic distance showed that the ‘Amba’ and ‘LuckyOne’ varieties had the lowest distance (0.329), and ‘Potomac’ and ‘Onnuri 2ho’ had the highest distance (0.437). The SSR data from bulked samples produced a UPGMA phylogenetic tree showing Korean varieties grouped with non-Korean varieties. Based on an analysis of genetic resources, these results can contribute to the creation of a core collection for orchardgrass conservation and breeding, as well as to the development of future varieties with beneficial traits.