Simple sequence repeat (SSR) markers for Elymus, Pseudoroegneria and Pascopyrum species (Triticeae: Gramineae)

The Triticeae tribe (Poaceae) includes several important cereal crops, cultivated forages, annual and perennial grass weeds and ecologically diverse native North American grasses. Elymus L. is the largest and most complex genus in the Triticeae tribe with approximately 150 polyploid perennial grass species occurring worldwide. The genomic constitutions of approximately 40% of the Elymus species are unknown. Molecular markers are needed to facilitate genetic analysis of diversity and functional traits in these species. We have developed simple sequence repeat (SSR) markers for use in Elymus based on Elymus expressed sequence tag sequences. To test the polymorphic content and transferability of these SSRs, 100 SSR primer pairs were tested on 84 plants representing seven North American Elymus, Pseudoroegneria and Pascopyrum species. The number of bands produced from each of the SSRs ranged from 1 to 11 with an average of 4.3 bands/SSR. A subset of the 23 most polymorphic SSRs produced 142 bands, an average of 6.2 bands/SSR. Binary data from the 100 SSRs successfully separated all individuals into their respective accessions in a neighbour-joining phylogram with a 100% confidence interval. Analysis of molecular variance showed that 29.9% of the total variation was within and 70.1% was among the accessions. These SSRs will be a useful tool for investigating genetic diversity, genome constitutions and molecular mapping in Elymus and other Triticeae grasses.