High elevation sites in the low mountain ranges in Germany are naturally covered by Norway spruce (Picea abies (Karst.) L.) stands. Historically, large scale anthropogenic range expansion starting in the mid to late 18th century had a huge impact on the forest composition throughout Germany. Utilisation and exploitation often led to artificial regeneration, mostly carried out using seeds from allochthonous provenances. Usually, autochthonous (natural) high elevation Norway spruce trees have narrow crown phenotypes, whereas lowland trees have broader crowns. Narrow crown phenotypes are likely the result of adaptation to heavy snow loads combined with high wind speeds. In the present study, neighbouring stand pairs of putative autochthonous and allochthonous origin with contrasting phenotypes in high elevation sites were investigated with 200 samples each. These stands are located in the Ore Mountains, the Thuringian Forest, and the Harz Mountains. Additionally, a relict population with the typical narrow high elevation phenotypes was sampled in Thuringia, known as “Schlossbergfichte”. The objective of the study was to quantify supposedly adaptive phenotypic differences in crown architecture and the genetic differentiation of 11 putatively neutral nuclear microsatellite markers (i.e., simple sequence repeats (nSSRs)). The high differentiation of morphological traits (P_ST = 0.952–0.989) between the neighbouring autochthonous and allochthonous stands of similar age contrasts with the very low neutral genetic differentiation (F_ST = 0.002–0.007; G″_ST = 0.002–0.030), suggesting that directional selection at adaptive gene loci was involved in phenotypic differentiation. Comparing the regions, a small isolation by distance effect for the Harz Mountains was detected, suggesting landscape resistance restricting gene flow. Finally, the differentiation of the very old autochthonous (up to 250 years) stand “Schlossbergfichte” with typical high elevation phenotypes could cohere with the sampling of a relict genepool.

The genus Abies is widely distributed across the world and is of high importance for forestry. Since chloroplasts are usually uniparentally inherited, they are an important tool for specific scientific issues like gene flow, parentage, migration and, in general, evolutionary analysis. Established genetic markers for organelles in conifers are rather limited to RFLP markers, which are more labour and time intensive, compared with SSR markers. Using QUIAGEN CLC Workbench 23.03, we aligned two chloroplast genomes from different Abies species (NCBI accessions: NC_039581, NC_042778, NC_039582, NC_042410, NC_035067, NC_062889, NC_042775, NC_057314, NC_041464, MH706706, MH047653 and MH510244) to identify potential SSR candidates. Further selection and development of forward and reverse primers was performed using the NCBI Primer Blast Server application. In this article, we introduce a remarkably polymorphic SSR marker set for various Abies species, which can be useful for other conifer genera, such as Cedrus, Pinus, Pseudotsuga or Picea. In total, 17 cpSSRs showed reliable amplification and polymorphisms in A. grandis with a total of 68 haplotypes detected. All 17 cpSSRs amplified in the tested Abies spp. In the other tested species, except for Taxus baccata, at least one primer was polymorphic.

Peer-reviewed, open access journal of forestry & environmental sciences

The analysis of genetic variation underlying local adaptation in natural populations, together with the response to different external stimuli, is currently a hot topic in forest sciences, with the aim of identifying genetic markers controlling key phenotypic traits of interest for their inclusion in restoration and breeding programs. In Europe, one of the main tree species is Norway spruce (Picea abies (L.) H.Karst.). Using the MassARRAY® platform, 568 trees from North Rhine‐Westphalia (Germany) were genotyped with 94 single nucleotide polymorphisms (SNPs) related to circadian and growth rhythms, and to stress response. The association analysis of the selected markers with health status and elevation was performed using three different methods, and those identified by at least two of these were considered as high confidence associated SNPs. While just five markers showed a weak association with health condition, 32 SNPs were correlated with elevation, six of which were considered as high confidence associated SNPs, as indicated by at least two different association methods. Among these genes, thioredoxin and pseudo response regulator 1 (PRR1) are involved in redox homeostasis and ROS detoxification, APETALA2‐like 3 (AP2L3), a transcription factor, is involved in seasonal apical growth, and a RPS2‐like is a disease resistance gene. The function of some of these genes in controlling light‐dependent reactions and metabolic processes suggests signatures of adaptation to local photoperiod and the synchronization of the circadian rhythm. This work provides new insights into the genetic basis of local adaptation over a shallow elevation gradient in Norway spruce.

Norway spruce differs little in neutral genetic markers among populations and provenances often reported, but in terms of putative adaptive traits and their candidate genes, some clear differences have been observed. This has previously been shown for crown morphotypes. Stands with mostly narrow crown shapes are adapted to high elevation conditions, but these stands are scattered, and the forest area is often occupied by planted stands with predominantly broad crowned morphotypes. This raises questions on whether this differentiation can remain despite gene flow, and on the level of gene flow between natural and planted stands growing in close neighbourhood. The locally adapted stands are a valuable seed source, the progeny of which is expected to have high genetic quality and germination ability. The presented case study is useful for spruce plantation by demonstrating evaluation of these expectations. Immigrant pollen and seeds from planted trees could be maladaptive and may alter the genetic composition of the progeny. This motivated us to study single tree progenies in a locally adapted stand with narrow crowned trees in a partial mast year at nuclear genomic simple sequence repeat (SSR) markers. Spruce is a typical open-pollinated conifer tree species with very low selfing rates, which were also observed in our study (s = 0.3–2.1%) and could be explained by efficient cross-pollination and postzygotic early embryo abortion, common in conifers. The estimated high amount of immigrant pollen found in the pooled seed lot (70.2–91.5%) is likely to influence the genetic composition of the seedlings. Notably, for individual mother trees located in the centre of the stand, up to 50% of the pollen was characterised as local. Seeds from these trees are therefore considered to retain most of the adaptive variance of the stand. Germination percentage varied greatly between half-sib families (3.6–61.9%) and was negatively correlated with relatedness and positively with effective pollen population size of the respective families. As pollen mostly originated from outside the stand and no family structures in the stand itself were found, germination differences can likely be explained by diversity differences in the individual pollen cloud.