Abstract
In Germany, Douglas fir (Pseudotsuga menziesii Franco) is seen as a valuable species for future cultivation in times of climate change. Local seed production in seed stands and seed orchards may secure that local adaptation is transferred to the next generation, but small population sizes could lower genetic diversity and thus future adaptability. Here we analyse the transfer of genetic diversity from parent to offspring generation in four older German seed orchards. We detected low pollen contamination rates due to high levels of spatial isolation. Even with a relatively low number of 40 clones, seed orchard design with randomized and repeated planting of clones led to low selfing rates, and despite uneven parental contributions, the number of successful parents and the level of genetic intermixture were high enough to allow the transfer of an adequate part of the genetic diversity to the next generation. Larger numbers, however, might be needed to reliably conserve the entire genetic diversity over succeeding generations. Conclusions on the establishment of future seed orchards and regarding areas requiring further research are drawn at the end of the paper.
Highlights
Douglas fir (Pseudotsuga menziesii Franco), a conifer native to western North America, was introduced to Europe about 190 years ago (Lavender and Hermann 2014)
A second hierarchic STRUCTURE analysis using only the parental clones of the three coastal “green” Douglas fir seed orchards showed no further differentiation between the seed orchards
The seed orchard design with randomized and repeated planting of clones led to low selfing rates and despite uneven parental contributions, the number of successful parents and the level of genetic intermixture were high enough to allow an adequate transfer of genetic diversity to the generation
Summary
Douglas fir (Pseudotsuga menziesii Franco), a conifer native to western North America, was introduced to Europe about 190 years ago (Lavender and Hermann 2014). Two different varieties of Douglas fir have been described, the coastal— so-called “green”- variety [Pseudotsuga menziesii var. Menziesii (Mirbel) Franco] growing on the North American Pacific Coast, and the inland—so-called “blue”- [Pseudotsuga menziesii var. Thünen Institute of Forest Genetics, Eberswalder Chaussee 3a, 15377 Waldsieversdorf, Germany. Most of the Douglas fir growing in Germany belongs to the coastal “green” variety, which performed better in European provenance field tests (Kleinschmit and Bastien 1992; Spellmann et al 2015)
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