Seed collected from some artificial stands of Douglas-fir produce trees having good adaptation to the local environment and substantial growth. The origin of these artificial stands is completely unknown and might be assessed by studying genetic variability and mating system, using isozymes as genetic markers. Three European artificial stands (Au Charnay, Barlohe, En Argaud) and 1 natural stand (Bacon Creek) of Washington State were analysed in the present study. No significant variation of allelic frequency was observed among stands or between generations (mother trees and offsprings); nevertheless the gene diversity in the progenies was reduced. According to a multivariate analysis, the genetic variation, was mainly within open progenies, and weakly among provenances (about 2%); artificial provenances could not be differentiated. The increase of homozygosity from mother trees to their progenies was general; it was higher than that expected from the observed outcrossing rate. This suggested pollination and crossing between related trees and neighbourhood effect, that was also supported by the difference between multilocus and single locus outcrossing rate. Different levels of crossing between related trees were assessed (more than 45 %) considering that fixation index resulted only from selfing and related mating. In 1 artificial provenance, the mother trees showed a weak and positive fixation index, and the level or related mating was relatively low. This artificial provenance (Au Charnay) may have resulted from a mixture of several progenies collected in different natural provenances, inducing a deficit of heterozygosity by structuring into subpopulations. Trees from seed collected in this stand produced a higher growth than those from En Argaud stand, which showed a presumed higher frequency of inbred mating.
