• EST-derived SSR markers used as anchor loci for the construction of a consensus linkage map in ryegrass (Lolium spp.)

      Studer, Bruno; Kolliker, Roland; Muylle, Hilde; Asp, Torben; Frei, Ursula; Roldan-Ruiz, Isabel; Barre, Philippe; Tomaszewski, Celine; Meally, Helena; Barth, Susanne; et al. (Biomed Central, 16/08/2010)
      Background: Genetic markers and linkage mapping are basic prerequisites for marker-assisted selection and map-based cloning. In the case of the key grassland species Lolium spp., numerous mapping populations have been developed and characterised for various traits. Although some genetic linkage maps of these populations have been aligned with each other using publicly available DNA markers, the number of common markers among genetic maps is still low, limiting the ability to compare candidate gene and QTL locations across germplasm. Results: A set of 204 expressed sequence tag (EST)-derived simple sequence repeat (SSR) markers has been assigned to map positions using eight different ryegrass mapping populations. Marker properties of a subset of 64 EST-SSRs were assessed in six to eight individuals of each mapping population and revealed 83% of the markers to be polymorphic in at least one population and an average number of alleles of 4.88. EST-SSR markers polymorphic in multiple populations served as anchor markers and allowed the construction of the first comprehensive consensus map for ryegrass. The integrated map was complemented with 97 SSRs from previously published linkage maps and finally contained 284 EST-derived and genomic SSR markers. The total map length was 742 centiMorgan (cM), ranging for individual chromosomes from 70 cM of linkage group (LG) 6 to 171 cM of LG 2. Conclusions: The consensus linkage map for ryegrass based on eight mapping populations and constructed using a large set of publicly available Lolium EST-SSRs mapped for the first time together with previously mapped SSR markers will allow for consolidating existing mapping and QTL information in ryegrass. Map and markers presented here will prove to be an asset in the development for both molecular breeding of ryegrass as well as comparative genetics and genomics within grass species.
    • Potential for gene-flow from cultivated Irish grasses and cereals

      Mullins, Ewen; Ryan, Eimear; Meade, Connor (Teagasc, 01/08/2009)
      The importance of gene movement from cultivated plants has been highlighted in regard to minimising the movement of seed and/or pollen between GM and non-GM crops (i.e. gene flow). Although ryegrass covers in excess of 90% of Ireland’s agricultural area, very little is known about gene flow from ryegrass populations from an Irish context. The goal of this project was to address this lack of data by measuring the degree of pollen-mediated gene-flow between two Lolium spp. in a field environment. Ryegrass (esp. Lolium perenne) was selected because as the dominant pasture grass it is critical for the livestock industry as well as being a current target for novel improvements. The results from this research indicate that the potential for pollen-mediated gene flow from perennial ryegrass decreases exponentially with increased distance from the pollen source, with hybridisation events recorded out at 192m. In parallel to this research, a separate study was conducted to assess the degree of genetic diversity within feral and wild Lolium spp across Ireland and also within the important crop weed Avena fatua (‘wild oats’); thereby providing an insight into the degree of historic gene flow that has occurred within each species and in regard to the latter, identifying the potential for non-native A. fatua to colonise the Irish agrienvironment.