An Update on the Classification of Kentucky Bluegrass Cultivars and Accessions Based on Microsatellite (SSR) Markers

Kentucky bluegrass (Poa pratensis L.) is an important perennial forage and amenity turfgrass species used throughout temperate regions in North America and Europe. Kentucky bluegrass cultivars and accessions exhibit a wide range of ploidy levels, morphological traits, turfgrass quality characteristics, and tolerances to both biotic and abiotic stresses. As such, cultivar classification systems have been developed to categorize Kentucky bluegrass cultivars and accessions on the basis of pedigree, turf performance, morphological traits, and genetic relatedness (DNA markers). The objectives of the current study were to assess the genetic diversity among and within Kentucky bluegrass entries using simple sequence repeat (SSR) markers, and to categorize new germplasm in the Kentucky bluegrass classification system. In this study, 21 SSR markers were used to genotype eight individuals from each of 144 bluegrass cultivars and accessions (1152 total samples). The SSR markers successfully categorized all entries into distinct classification groups and provided justification for a partial revision to the previous DNA marker-based classification system. The majority of cultivars and accessions were uniquely identified with the current set of SSR markers, and SSR marker-based genetic relationships of individuals within classification types showed agreement with breeding history records. Over 60 new Kentucky bluegrass National Turfgrass Evaluation Program entries were placed into updated classification groups, and the SSR markers used in this study can be used in the future to genotype and assign new cultivars and accessions into Kentucky bluegrass classification types and assess the genetic relatedness among entries.