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Genetic variation at 13 polymorphic enzyme loci was studied in progenies from seed orchards and natural populations of Pinus sylvestris in Sweden. Progenies were analysed at two life stages: embryos and 9-11 year old trees. Measures of genetic diversity for the 13 loci revealed much variability in the progenies studied. There was no visible reduction of the genetic diversity in the orchard progenies compared to progenies from natural populations. The average fixation indices in embryos were high and positive, probably due to the occurrence of inbred individuals. A trend of higher fixation indices in the progenies from the northern seed orchards and natural populations was observed. Increased selfing due to scarce and uneven flowering in the northern populations could account for this result. In addition, high fixation indices found in the northernmost seed orchard could also result from the restricted pollen flow between the blocks in this orchard. The young trees planted 9-11 years ago in the field had low fixation indices indicating that excess homozygosity observed in embryos had been eliminated during later stages of development.
Key words: Pinus sylvestris, seed orchards, pollen migration, gene diversity, allozymes, domestication
by Alfred E. Szmidt