BREEDING VALUE OF BASE-POPULATIONS DERIVED FROM CONTIGUOUS CLUSTERS IN PERENNIAL RYEGRASS

Five broad-based breeding populations were produced by polycrossing na tural populations sampled in five clusters developed by a hierarchical method with a geographic-contiguity constraint. As a result, each of these breeding populations originates from a single region and the pop ulations within a cluster are more likely to share the same alleles wi th similar frequencies. A single generation of intercrossing would the refore be sufficient to establish a panmixia equilibrium. These popula tions were tested for dry-matter yield in plots and compared to contro l cultivars in two locations. There were some trends of specific adapt ation related to the geographic origin of populations, which, on avera ge, compared well to controls. Their half-sib families were evaluated as spaced plants in one location. This allowed genetic parameters and expected response to selection to be computed. Three out of five breed ing populations appeared to be promising for the development of new, i mproved synthetic varieties.