RAPD-Based Genetic Relationships in Kentucky Bluegrass

Kentucky bluegrass (Poa pratensis L.) is a widely used, facultatively apomictic, cool season turf and forage grass, with many known cultivars. Previously these have been classified on the basis of morphological traits in field tests. However, these determinations are lengthy, sensitive to environmental variations, and there are few traits that can be tested. Molecular markers provide an alternative way to classify these cultivars. Important advantages of molecular markers include lack of sensitivity to changes in environmental conditions, as well as a nearly unlimited potential number of markers and speed of the marker assays as compared with field tests. They can also provide additional information such as the amount of genetic divergence between Kentucky bluegrass cultivars and other genotypes, the amount of agreement between morphological and marker-based classification, and the amount of genetic variability between seedling replicates of genotypes. Random amplified polymorphic DNA (RAPD) marker data was collected from three replicates each of 123 Kentucky bluegrass cultivars, plant introductions (PIs), experimental breeding lines, and interspecific hybrids between Kentucky and Texas bluegrass (Poa arachnifera Torr.). From these data multidimensional scaling (MDS) plots were created, and ANOVA tests of significant differences between germplasm sources were performed. The PIs were the most genetically divergent from the cultivars, while the interspecific hybrids were not as distinct. Members of two morphological trait-based types were found to be genetically similar, and there was a wide range of genetic variability among germplasm sources. The genetic divergence of the PIs, combined with their potentially high turf utility reported in earlier studies, indicates their potential as a genetic resource. All but two of the morphological trait-based types contained genetically diverse individuals, so that cultivar blends of all but these two types would be morphologically similar yet genetically diverse. The rather high within-cultivar genetic variability could be due to a relatively high proportion of potentially sexually produced off-types. Thus, this study provides further evidence for the utility of RAPD markers for turfgrass genetics, as well as important genetic information for turf breeders and managers.