Assessing the abundance and polymorphism of simple sequence repeats in perennial ryegrass

Simple sequence repeats (SSRs) have proven to be useful genetic markers in a wide variety of plants, hut have yet to be widely applied to turfgrasses, Here we describe a study of SSRs in perennial ryegrass (Lolium perenne L.) . A library of perennial ryegrass genomic DNA was screened with (GA)(n) and (GT), probes, and SSR containing clones were isolated and sequenced. On th e basis of this screen, me estimated that there are roughly 5800 (GA)(n) an d (GT)(n) SSRs in the haploid perennial ryegrass genome. Polymerase chain r eaction (PCR) primers were designed to amplify the isolated SSRs, and six p olymorphic SSRs were identified. Polymorphism in the these six SSRs was suf ficient to discriminate among 18 individuals representing Il perennial ryeg rass clones and seven other Lolium species. Half-sibs could be distinguishe d with data from as fem as three SSRs, The SSR genotype data,vas also used to infer genetic relationships among the individuals of our sample. The rel ationships were in broad agreement with those established by previous analy ses, suggesting that SSR data will be useful for exploring relationships am ong perennial ryegrass cultivars, In total, this study indicates that SSRs are sufficiently abundant and sufficiently polymorphic to be useful genetic markers in perennial ryegrass.