The Development of a BAC-fingerprint FPC map for Lolium perenne

Perennial ryegrass (L. perenne) is the most important forage grass in the UK and temperate areas worldwide and is the mainstay of grassland-based farming systems in these areas. Taxonomically, perennial ryegrass is a member of the sub-family Pooideae, along with Brachypodium, the Triticeae cereals and oats. The genome size is estimated at 2-2.5Gb and comparative mapping indicates the seven chromosomes of ryegrass are basically syntenic with those of barley and wheat. Consequently, there is interest in developing genome resources for perennial ryegrass both from its agricultural and its evolutionary significance. As part of these genome resources we are producing a BAC-based physical map derived from high information content fingerprints (HICF) and BAC-end sequences (BES). To achieve this, we have constructed 2 BAC libraries (Hind III and BstY1) from an inbred perennial ryegrass genotype which, together, give a projected genome coverage of 10-15x. The initial assembly of the fingerprint data using Fingerprint Contig (FPC) software identifies 4029 contigs with 2965 singletons. Additionally, we have generated BAC library PCR screening pools for both libraries using the ‘superpool and matrix pool’ approach (Amplicon Express). These are being used to assign genetically mapped markers in perennial ryegrass to BACs and so FPC contigs. Currently, we are manually editing the FPC phase 1 assembly and incorporating the BES and other genetic and genomic resources to validate the derived contigs. In the future, this physical map will be used to complement next generation sequencing-based approaches for developing whole genome sequence assemblies for perennial ryegrass.