Molecular Markers Highlight Variation within and among Kentucky Bluegrass Varieties and Accessions

Assessing relationships among germplasm and cultivars of Kentucky bluegrass (Poa pratensis L.) is limited to field evaluations or a small set of molecular markers. To improve the efficiency of characterizing Kentucky bluegrass cultivars and germplasm, this study was designed to develop a larger set of robust molecular makers and a concise panel of cultivars to assess relationships of Kentucky bluegrass. An extensive library of simple sequence repeat markers was developed and used to assess relationships among and within 24 cultivars and accessions. Plants generally grouped as cultivars in cluster analysis, but molecular outlying plants and phenotypic off-type plants were found in 15 of the entries. The cultivars represented the major Kentucky bluegrass classification types and were consistent with previous reports. Salt-tolerant National Plant Germplasm System accessions were placed in context with the cultivars and grouped closest to the Eurasian/Common type cultivar Kenblue. Similarity of plants within cultivars varied from 60 to 98% but never reached 100%. These data showed that, with two exceptions, the cultivars could represent the major Kentucky bluegrass classification types and also that molecular variation exists within putatively apomictic plants.