INFLUENCE OF RECOMBINATION ON GENETIC-VAR IABILITY .2. SIMULATION STUDIES

Two stimulation studies were carried out to complement an experimental study of the possible interest for plant breeders of an allele increa sing recombination rates. In the first simulation study, 4 populations of 10 individuals were simulated in the case of high (45%), medium (1 9.6%) and low (6.9%) recombination frequencies. Ten-plant populations were derived by one generation, either from selfing or from crossing i n a circular mating design, from each of the 4 populations. For each i nitial population, the distribution of the genetic variances in the po pulations obtained by one mating system overlapped widely in the 3 cas es of recombination rates considered, whether the initial population p resented an excess of coupling phase, or an excess of repulsion phase. An experimental assessment of the effect of recombination rate differ ences on genetic variability of quantitative traits is therefore likel y to be difficult. The second study simulated a recurrent selection pr ogram in the case of high (45%), medium (19.6%) and low (9%) recombina tion rates. The mean genetic value increased somewhat more slowly and reached a slightly lower value for low recombination rates, whereas th e genetic variance remained the highest after the second selection cyc le. The evolutions in genetic mean values and genetic variances were a lmost identical for medium and high recombination frequencies. Thus, a n allele which increases recombination rates will only be of interest in the case of close linkage or difficult crossing. Otherwise, a circu lar mating design manages efficiently the initial germplasm.