Introgression mapping in the grasses. II. Meiotic analysis of the Lolium perenne/Festuca pratensis triploid hybrid

Abstract

Lolium perenne/Lolium perenne/Festuca pratensis triploid hybrids are a potentially important source of material for determining the genetic control of agronomically and scientifically important characters and determining how genetic maps relate to physical maps. The evolutionary relationship between L. perenne (Lp) and F. pratensis (Fp) is, however, unclear. In order to determine the genomic relationships between Lp and Fp, genomic in situ hybridization (GISH) and the Chapman and Kimber mathematical model (1992) were used to analyse metaphase I in meiocytes of an LpLpFp triploid hybrid. Both analyses clearly demonstrated that recombination occurs preferentially between the homologous Lp genomes in the LpLpFp triploid, indicating that the genomes of the two species have diverged. Direct analysis of homologous vs. homoeologous chromosome association, as measured by GISH, was in broad agreement with the mathematical analysis. It is therefore concluded that the Chapman and Kimber model (1992) is a valid means of assessing chromosome pairing in these triploid hybrids. The significance of the data for elucidating the closeness of the relationship of L. perenne and F. pratensis is discussed.