The use of molecular markers in conservation programmes of live animals

Monte Carlo simulation has been carried out to study the benefits of using molecular markers in a conservation programme to minimize the homozygosity by descent in the overall genome. Selection of the breeding individuals was either at random or based on two alternative criteria: overall heterozygos ity of the markers or frequency-dependent selection. Even molecular informa tion was available for all the 1 900 simulated loci, a conventional tactic such as restriction in the variance of the family size is the most importan t strategy for maintaining genetic variability. In this context: a) frequen cy-dependent selection seems to be a more efficient criterion than selectio n for heterozygosity; and b) the value of marker information increases as t he selection intensity increases. Results from more realistic cases (1, 2, 3, 4, 6 or 10 markers per chromosome and 2, 4, 6 or 10 alleles per marker) confirm the above conclusions. This is an expensive strategy with respect t o the number of candidates and the number of markers required in order to o btain substantial benefits, the usefulness of a marker being related to the number of alleles. The minimum coancestry mating system was also compared with random mating and it is concluded that it is advantageous at least for many generations. (C) Inra/Elsevier, Paris.