Submitted to: Canadian Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2008
Publication Date: April 4, 2008
Citation: Jones, T.A., Larson, S.R., Wilson, B.L. 2008. Genetic Differentiation and Hybridization Among Festuca Idahoensis, F. Roemeri, and F. Ovina Detected From AFLP, ITS, and Chloroplast DNA. Botany 86:422-434 Interpretive Summary: Roemer fescue (Festuca roemeri) is a newly recognized species previously considered a part of the Idaho fescue (F. idahoensis) taxon. These important natural forage grasses are native to North America, but considered closely related to the globally distributed sheep fescue species complex (F. ovina sensu lato). Roemer fescue and sheep fescue are separately distributed, throughout much of the Pacific Northwest, west and east of the Cascade and Sierra-Nevada mountain range, respectively. Maternally inherited chloroplast DNA sequences, biparentally inherited nuclear ribosomal DNA sequences, and six AFLP-based DNA fingerprinting profiles were used to test and characterize genetic distinctiveness and relationships between Roemer fescue, Idaho fescue, and sheep fescue. Genetic analyses grouped most plants into groups corresponding to taxa, although some admixture of Idaho fescue and Roemer's fescue was detectable in the multiple-origin cultivars, Joseph and NezPurs, and in some natural-source accession collected in the geographic suture zone of these two taxa. Moreover, natural hybrids of native Idaho fescue and introduced sheep fescue were also found. In summary, results indicated that Roemer fescue and Idaho fescue are genetically distinct, but closely related to each other and to sheep fescue.
Technical Abstract: North American forms of the F. ovina complex, Festuca idahoensis and F. roemert are distributed broadly east and narrowly west of the Cascade Mountains, respectively. The psbA-trnH and rps16-trnK chloroplast DNA intergenic sequences, 18S-5.8S-26S nuclear ribosomal DNA internal transcribed spacer (ITS) sequences, and six AFLP primer combinations were used to investigate genetic relatedness and differences among 327 plant samples from 24F. idahoensis and 33 F. roemeri natural-source germplasm accessions; two multiple-origin F. idahoensis x F. roemeri cultivars; one apparently admixed F. ovina x F. idahoensis accession; four naturalized or cultivated varieties of Eurasian-source F. ovina sensu lato; and several F. arizonica, F. occidentalis, and F. rubra reference accessions. The AFLP profiles of individual plants were unique, but distance-based and Bayesian model-based clustering separated AFLP genotypes into groups corresponding to taxa. Approximately 15.9% of the AFLP variation was apportioned between F. idahoensis and F. roemeri, with the remaining 61.2% and 22.9% variation maintained within and among natural-source accessions, respectively. However, genetic admixture between F. idahoensis, F. roemeri, and F. ovina was detectable and DNA sequence divergence was very low in the chloroplast and ITS regions. The latter three taxa are genetically differentiated but have been hybridized in natural collecitons and varieties.