PHYSICAL MAPPING IN THE GRASSES

¹ Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, Wales, UK

² Institute of Biological Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3EB, Wales, UK

³ School of Biological Sciences, The University of Birmingham, Birmingham B15 2TT, UK

A Lolium perenne (4x)/Festuca pratensis (2x) triploid hybrid (2n=3x=21) was produced and backcrossed to diploid Lolium perenne. Meiotic analysis of the LpLpFp triploid hybrid using genomic in situ hybridization (GISH) revealed that the L.perenne genomes recombined preferentially, however, the frequency of L.perenne/F.pratensis homoeologous recombination was still very high, i.e. 33%. The BC₁ progeny which predominantly had 14 chromosomes, was also analysed using GISH and genetic markers. GISH revealed that over 74% of the BC₁ individuals carried one or more F. pratensis chromosome segments. By comparing the physical size of introgressed F. pratensis chromosome segments with the presence or absence of F. pratensis-specific polymorphisms it was possible to determine the physical position of genetic markers. A comparison of the physical position of genetic markers relative to their genetic position is allowing the alignment of physical and genetic maps in the grasses. Initial results indicate that the highest frequency of recombination occurs interstitially while the lowest frequency of recombination occurs in the centromeric and telomeric regions.