title: Assessment of genetic diversity in Nordic timothy (Phleum pratenseL.).
abstract: BACKGROUND
  Timothy (Phleum pratenseL.), a cool-season hexaploid perennial, is the most important forage grass species in Nordic countries. Earlier analyses of genetic diversity in a collection of 96 genebank accessions of timothy with SSR markers demonstrated high levels of diversity but could not resolve population structure. Therefore, we examined a subset of 51 accessions with REMAP markers, which are based on retrotransposons, and compared the diversity results with those obtained with SSR markers.
  
  
  RESULTS
  Using four primer combinations, 533 REMAP markers were analyzed, compared with 464 polymorphic alleles in the 13 SSR loci previously. The average marker index, which describes information obtained per experiment (per primer combination or locus) was over six times higher with REMAPs. Most of the variation found was within accessions, with somewhat less, 89 %, for REMAPs, than for SSR, with 93 %.
  
  
  CONCLUSIONS
  SSRs revealed differences in the level of diversity slightly better than REMAPs but neither marker type could reveal any clear clustering of accessions based on countries, vegetation zones, or different cultivar types. In our study, reliable evaluation of SSR allele dosages was not possible, so each allele had to be handled as a dominant marker. SSR and REMAP, which report from different mechanisms of generating genetic diversity and from different genomic regions, together indicate a lack of population structure. Taken together, this likely reflects the outcrossing and hexaploid nature of timothy rather than failures of either marker system.
authors.affiliation: Green Technology, Natural Resources Institute Finland (Luke), Myllytie 1, FI-31600 Jokioinen, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Tanhuanpää
authors.affiliation: Internal Expert Services, Natural Resources Institute Finland (Luke), Humppilantie 14, FI-31600 Jokioinen, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Erkkilä
authors.affiliation: Internal Expert Services, Natural Resources Institute Finland (Luke), Humppilantie 14, FI-31600 Jokioinen, Finland.
authors.forename: Ruslan
authors.initials: R
authors.lastname: Kalendar
authors.affiliation: Green Technology, Natural Resources Institute Finland (Luke), Myllytie 1, FI-31600 Jokioinen, Finland ; Luke/BI Plant Genome Dynamics Laboratory, Institute of Biotechnology, Viikki Biocenter, University of Helsinki, P.O. Box 56, Viikinkaari 1, FI-00014 Helsinki, Finland.
authors.forename: Alan Howard
authors.initials: AH
authors.lastname: Schulman
authors.affiliation: Boreal Plant Breeding Ltd, Myllytie 10, FI-31600 Jokioinen, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Manninen
mesh_terms: D000483:Alleles; D018744:DNA, Plant / Q000235:genetics; D005819:Genetic Markers; D014644:Genetic Variation; D018745:Genome, Plant; D018895:Microsatellite Repeats; D031784:Phleum / Q000235:genetics*; D018626:Retroelements; D012537:Scandinavian and Nordic Countries
chemical_list: D018744:DNA, Plant; D005819:Genetic Markers; D018626:Retroelements
keywords: Genetic diversity; Genetic structure; Microsatellite; Phleum pratense L; REMAP; Retrotransposon marker; SSR; Timothy