Abstract
BackgroundRyegrasses and fescues (genera, Lolium and Festuca) are species of forage and turf grasses which are used widely in agricultural and amenity situations. They are classified within the sub-family Pooideae and so are closely related to Brachypodium distachyon, wheat, barley, rye and oats. Recently, a DArT array has been developed which can be used in generating marker and mapping information for ryegrasses and fescues. This represents a potential common marker set for ryegrass and fescue researchers which can be linked through to comparative genomic information for the grasses.ResultsA F2 perennial ryegrass genetic map was developed consisting of 7 linkage groups defined by 1316 markers and deriving a total map length of 683 cM. The marker set included 866 DArT and 315 gene sequence-based markers. Comparison with previous DArT mapping studies in perennial and Italian ryegrass (L. multiflorum) identified 87 and 105 DArT markers in common, respectively, of which 94% and 87% mapped to homoeologous linkage groups. A similar comparison with meadow fescue (F. pratensis) identified only 28 DArT markers in common, of which c. 50% mapped to non-homoelogous linkage groups. In L. perenne, the genetic distance spanned by the DArT markers encompassed the majority of the regions that could be described in terms of comparative genomic relationships with rice, Brachypodium distachyon, and Sorghum bicolor.ConclusionsDArT markers are likely to be a useful common marker resource for ryegrasses and fescues, though the success in aligning different populations through the mapping of common markers will be influenced by degrees of population interrelatedness. The detailed mapping of DArT and gene-based markers in this study potentially allows comparative relationships to be derived in future mapping populations characterised using solely DArT markers.
Highlights
Ryegrasses and fescues are species of forage and turf grasses which are used widely in agricultural and amenity situations
Marker-based maps have progressed from linkage groups developed largely from restriction fragmentlength polymorphisms (RFLPs) [1,2,3,4,5] to those developed from combinations of random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphisms (AFLPs) and microsatellites/simple sequence repeats (SSRs) [6,7,8,9,10,11,12,13]
Genetic mapping Genetic mapping using JoinMap3.0 incorporated the new Diversity Array Technology (DArT) data into the existing framework maps for this F2 population giving an overall map length of 683 cM defined by 1316 markers; an additional 66 DArT, 3 SNP, 3 SSR and a single AFLP marker could be assigned ‘best-fit’ positions (Additional file 1)
Summary
Ryegrasses and fescues (genera, Lolium and Festuca) are species of forage and turf grasses which are used widely in agricultural and amenity situations. Marker-based maps have progressed from linkage groups developed largely from restriction fragmentlength polymorphisms (RFLPs) [1,2,3,4,5] to those developed from combinations of random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphisms (AFLPs) and microsatellites/simple sequence repeats (SSRs) [6,7,8,9,10,11,12,13] While these have delivered their immediate aims, the lack of a comprehensive common set of reference markers has limited the number of opportunities to align these maps and, so, the associated trait data produced for different studies. The publication of perennial and Italian ryegrass and meadow fescue genetic maps and analyses of Lolium x Festuca hybrids [16,17] integrating DArT markers indicates that this process is underway
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