'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 POLYCROSS BREEDING OF PERENNIAL RYEGRASS BASED ON MOLECULAR MARKER DIVERSITY R. KÖLLIKER, B. BOLLER, Y. HÄFELE, F. WIDMER Federal Institute for Agroecology and Agriculture, FAL Reckenholz, 8046 Zurich, Switzerland

Cultivars of perennial ryegrass are generally obtained by polycrossing several parental individuals.  Genetic diversity may be an important criterion for the selection of suitable parental combinations, but is difficult to assess based on phenotypic traits.  We used molecular markers to analyse genetic variability within selected breeding germplasm.  108 plants were investigated.  A considerable range of diversity was observed and molecular data correlated with a breeding history of the plants.  Polycrosses of six parental plants with different levels of genetic diversity were composed.  The level of diversity was more than 30% lower in “low diversity” crosses when compared to “high diversity” crosses. These polycrosses provide a valuable system to study the effect of genetic diversity of parental plants on diversity and performance of synthetic cultivars.