Genetic variation and mating system in a native provenance and the derived seed orchard of Douglas-fir (Pseudotsuga menziesii (Mirb.)Franco)

1998

S.201-209

2 Tab., zahlr. Lit.

Unselbständiges Werk

200055360

Genetic diversity and mating system were assessed in Douglas-fir (Pseudotsuga menziesii) in two stands (Darrington IUFRO and Round Mountain) of the Darrington provenance area, and in the seed orchard established in France with clones derived from this provenance area. Genotypes of embryos and megagametophytes of about 10 seeds per mother tree were determined at 10 independent isozyme loci. This allowed genotyping of mother-tree. Fixation indices were higher in progenies than in mother-trees, however significant deviations from Hardy-Weinberg equilibrium were detected only at some loci in progenies with an excess of homozygosity, both in the natural stands and in the seed orchard. Genetic differentiation was very low (FST<0.03) among natural stands, as well as among generations (FST<0.005). All stands were predominantly allogamous (multilocus outcrossing rate > 0.90). The highest outcrossing rate (0.97) was noticed in the seed orchard. The difference between the expected fixation index based on this multilocus outcrossing rate and the observed values in mother-trees and progenies suggested a higher level of inbreeding in the Round Mountain stand than in the Darrington IUFRO stand. The seed orchard consisting of 70 phenotypically selected clones showed the same level of genetic variability than the original stands, but it exhibited a reduced genetic diversity at the progeny level.