Non-native forest tree species have been introduced in Europe since the 16th century, but only in the second half of the 20th century the significance of the seed source origin for their economic use was recognized, resulting in the establishment of numerous provenance trials at a national, regional, European and International level, as those led by IUFRO. Breeding programs have also been launched in the continent for the most economically important species. Aim of this work is the formulation of provenance recommendations for planting of five non-native tree species in Europe (Douglas fir, grand fir, Sitka spruce, lodgepole pine and black locust), based on the information obtained from twenty countries, in the frame of the EU FP-1403 NNEXT Cost Action. The survey revealed that official and non-official national recommendations, based on provenance research results, have been elaborated and followed at a different level and extend for the above five species, but only for Douglas fir recommendations exist in almost all the participating to the survey countries. The compilation of provenance recommendations across Europe for each species is presented in the current work. Besides the recommended introduced seed sources, European seed sources are also preferred for planting, due to ease of access and high availability of forest reproductive material. European breeding programs yielding genetic material of high productivity and quality constitute currently the seed source of choice for several species and countries. Consolidation of trial data obtained across countries will allow the joint analysis that is urgently needed to draw solid conclusions, and will facilitate the development of ‘Universal-Response-Functions’ for the species of interest, rendering possible the identification of the genetic material suitable for global change. New provenance trial series that will test seed sources from the entire climatic range of the species, established in sites falling within and outside the environmental envelopes of their natural ranges, are urgently needed to pinpoint and understand the species-specific climate constraints, as well as to correlate functional traits to the seed origin and the environmental conditions of the test sites, so that the selection of suitable forest reproductive material of non-native tree species in the face of climate change can be feasible.

Diplodia sapinea is a cosmopolitan endophyte and opportunistic pathogen having occurred on several conifer species in Europe for at least 200 years. In Europe, disease outbreaks have increased on several Pinus spp. in the last few decades. In this study, the genetic structure of the European and western Asian D. sapinea population were investigated using 13 microsatellite markers. In total, 425 isolates from 15 countries were analysed. A high clonal fraction and low genetic distance between most subpopulations was found. One single haplotype dominates the European population, being represented by 45.3% of all isolates and found in nearly all investigated countries. Three genetically distinct subpopulations were found: Central/North European, Italian and Georgian. The recently detected subpopulations of D. sapinea in northern Europe (Estonia) share several haplotypes with the German subpopulation. The northern European subpopulations (Latvia, Estonia and Finland) show relatively high genetic diversity compared to those in central Europe suggesting either that the fungus has existed in the North in an asymptomatic/endophytic mode for a long time or that it has spread recently by multiple introductions. Considerable genetic diversity was found even among isolates of a single tree as 16 isolates from a single tree resulted in lower clonal fraction index than most subpopulations in Europe, which might reflect cryptic sexual proliferation. According to currently published allelic patterns, D. sapinea most likely originates from North America or from some unsampled population in Asia or central America. In order to enable the detection of endophytic or latent infections of planting stock by D. sapinea, new species-specific PCR primers (DiSapi-F and Diplo-R) were designed. During the search for Diplodia isolates across the world for species specific primer development, we identified D. africana in California, USA, and in the Canary Islands, which are the first records of this species in North America and in Spain.

The choice of seed material (genetics) is one of the tools that can improve adaptation to the changing climate. Insufficient adaptation can result in a number of potential risks, including stem cracking. The goal of this study is to assess the influence of genetics and wood properties on stem cracking in Norway spruce (Picea abies Karst). The study was conducted on a 35-year-old provenance trial in Eastern Latvia. Stem cracks were assessed using a six-score scale. Tree-ring parameters, i.e., latewood proportion, maximum and mean density, mean earlywood, and latewood density were analysed. The overall incidence of stem cracking was 23.5%, varying between 0% and 79% at a family mean level. Heritability of stem cracking was low, ca., two times lower than for the diameter at breast height (DBH): h² = 0.09 and 0.21, respectively. There were non-significant family and provenance effects on the occurrence of stem cracks, and weak family mean correlations between DBH, and the proportion of trees with any stem cracks or severe stem cracks. Overall, larger trees were more prone to cracking irrespective of provenance or family. Cracked trees had lower wood density parameters than unaffected trees, yet the latewood proportion was similar. Silvicultural treatments or selection to improve wood density could be suggested to reduce the risk of stem cracking.

In Europe, numerous Norway spruce (Picea abies L. Karst.) provenance trials have been established and evaluated at a juvenile age. Still, information about the adaptation potential and long-term fitness of transferred seedlots in the Baltic Sea region is lacking. The aim of the study was to evaluate the adaptation capacity of provenances and assess the patterns of their long-term reaction to environmental transfer. We examined a 32-year-old provenance trial in the mild Baltic Sea coastal climate of Western Latvia. Significant differences in height and stem volume were observed among provenances. Growth superiority for certain local and Carpathian provenances was maintained over more than one-third of the rotation period. The best predictor of climate transfer functions was minimum temperature of the coldest month at the place of origin, explaining 28% variation in tree height. Populations from sites with more frost days and a colder mean annual temperature, minimum temperature, and lower annual heat-moisture index than the planting site were generally taller.

Scots pine (Pinus sylvestris L.) is a key species in boreal forests, valued both economically and ecologically, in part due to its associations with foliar fungi. These fungi influence plant health, nutrient cycling, and resistance induction. To investigate these interactions, we collected 1367 needle and shoot samples across 12 plus tree genotypes grown in 4 progeny trials in Estonia. Amplifying the ITS1-5.8S-ITS2 gene region, we obtained over 1.3 million high-quality sequences and identified 1261 fungal OTUs at the 98% species hypothesis level. Among the identified OTUs, 24.6% were classified as saprotrophic and 18.2% as pathogenic fungi. Fungal diversity varied significantly between tree tissue types, progeny trial locations, and plus tree origins. Fungal community composition varied across tissue types, with older needles tending to harbor more complex communities. Plus trees 593 and 267-1 progenies stood out for their high phyllosphere fungal richness, and genotype-specific correlations indicated associations between fungal diversity and tree height or needle retention, suggesting potential genotype-dependent effects on tree performance. Heritability of fungal diversity between ramets in seed orchard and progeny trees was found for saprotrophic fungi but was negligible for total fungi and pathogens, indicating strong influence of microclimate conditions. These findings underscore the potential value of integrating fungal community traits into Scots pine breeding programs. Considering microbial associations alongside traditional growth traits may help identify genotypes better suited for future forestry needs under changing environmental conditions. Additionally, Setomelanomma holmii is reported here as a new fungal pathogen on Scots pine shoots in Estonia.