Fine fescue species determination by laser flow cytometry

The close morphological resemblance among fine fescues (Festuca spp.) makes identification and classification of species a difficult problem for turfgrass and taxonomic scientists. Determining ploidy level has become a major taxonomic tool for identifying species of fine fescues. The present study used laser flow cytometry to determine ploidy levels of 48 fine rescue populations (accessions) and thereby infer species classification based on observed and previously reported chromosome numbers. The 10 species of fine fescues examined were strong creeping red rescue (F. rubra L. spp. rubra), slender creeping red fescue (F. rubra var. littoralis Vasey), Chewings fescue [F. rubra ssp. fallax (Thuill.) Nyman], hard fescue (F. brevipila Tracey), sheep rescue [F. ovina L. ssp. hirtula (Hackel ex Travis) Wilkinson], hair rescue (F. filiformis Pourret), false sheep fescue (F. pseudovina Hackel ex Wiesb), alpine fescue (F. brachyphylla Schultes), bluebunch fescue (F. idahoensis Elmer), and tundra fescue (F. lenensis Drobov). Significant differences were observed between species (P < 0.01) and among populations within species (P < 0.05). DNA content among the 10 species was observed to be highly positively correlated with observed or reported chromosome numbers (r = 0.97, n = 10, P < 0.01). Linear regression analysis (Y = 2.1 + 0.23 X) predicted 2C DNA content values for each of the four ploidy levels to be 5.31 pg for diploids (2n = 2x = 14), 8.53 pg for tetraploids (2n = 4x = 28), 11.75 pg for hexaploids (2n = 6x = 42), and 14.98 pg for octoploids (2n = 8x = 56). The observations and results of the present study are consistent with current taxonomic treatments of hard and sheep fescue species as well as the other fine fescue species examined. The information presented should aid breeders in accurately and easily determining primary breeding germplasm with respect to ploidy levels. It may also enable the turfgrass industry to define reliably seed products and the plant collector to begin to assign native and/or naturalized accessions to their proper species categories.