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Background: Despite the increasing number of epigenomic studies in plants, little is known about the forces that shape the methylome in long-lived woody perennials. The Lombardy poplar offers an ideal opportunity to investigate the impact of the individual environmental history of trees on the methylome. Results: We present the results of three interconnected experiments on Lombardy poplar. In the first experiment, we investigated methylome variability during a growing season and across vegetatively reproduced generations. We found that ramets collected over Europe and raised in common conditions have stable methylomes in symmetrical CG-contexts. In contrast, seasonal dynamics occurred in methylation patterns in CHH context. In the second experiment, we investigated whether methylome patterns of plants grown in a non-parental environment correlate with the parental climate. We did not observe a biological relevant pattern that significantly correlates with the parental climate. Finally, we investigated whether the parental environment has persistent carry-over effects on the vegetative offspring's phenotype. We combined new bud set observations of three consecutive growing seasons with former published bud set data. Using a linear mixed effects analysis, we found a statistically significant but weak short-term, parental carry-over effect on the timing of bud set. However, this effect was negligible compared to the direct effects of the offspring environment. Conclusions: Genome-wide cytosine methylation patterns in symmetrical CG-context are stable in Lombardy poplar and appear to be mainly the result of random processes. In this widespread poplar clone, methylation patterns in CG-context can be used as biomarkers to infer a common ancestor and thus to investigate the recent environmental history of a specific Lombardy poplar. The Lombardy poplar shows high phenotypic plasticity in a novel environment which enabled this clonal tree to adapt and survive all over the temperate regions of the world. [ABSTRACT FROM AUTHOR]

The Black poplar is a pioneer tree species occurring along many river courses across Europe. Seedlings establish at very high density and experience various stresses (e.g., hydric, mechanical). In a previous study conducted in 2017 on the same population we described the fine-scale genetic structure (FSGS) of three age cohorts (5, 10 and > 20 years old) and found a significant SGS in the younger cohort. In this study, we aim to determine the FSGS in Black poplar cohorts of one-year-old seedlings, which is the most informative about seed dispersal. We used microsatellite markers to explore the FSGS of four different patches of Back poplar seedlings from two riverbanks in the Val d'Allier National Natural Reserve (France). We found a high genetic diversity and detected no FSGS in any of the four sampled seedlings patches. The absence of SGS at the seedling stage suggests that in this natural population, seeds from different mother trees are widely dispersed, well mixed and are deposited homogeneously on the various germination sites available over few kilometres. [ABSTRACT FROM AUTHOR]

Context: Black poplar (Populus nigra L.) is a keystone species of European riparian ecosystems that has been negatively impacted by riverside urbanization for centuries. Consequently, it has become an endangered tree species in many European countries. The establishment of a suitable rescue plan of the remaining black poplar forest stands requires a preliminary knowledge about the distribution of genetic variation among species populations. However, for some parts of the P. nigra distribution in Europe, the genetic resources and demographic history remain poorly recognized. Aims: Here, we present the first study on identifying and characterizing the genetic resources of black poplar from the Oder valley in Poland. This study (1) assessed the genetic variability and effective population size of populations and (2) examined whether gene flow is limited by distance or there is a single migrant pool along the studied river system. Methods: A total of 582 poplar trees derived from nine black poplar populations were investigated with nuclear microsatellite markers. Results: (1) The allelic richness and heterozygosity level were high and comparable between populations. (2) The genetic structure of the studied poplar stands was not homogenous. (3) The signatures of past bottlenecks were detected. Conclusion: Our study (1) provides evidence for genetic substructuring of natural black poplar populations from the studied river catchment, which is not a frequent phenomenon reported for this species in Europe, and (2) indicates which poplar stands may serve as new genetic conservation units (GCUs) of this species in Europe. Key message: The genetic resources of black poplar in the Oder River valley are still substantial compared to those reported for rivers in Western Europe. On the other hand, clear signals of isolation by distance and genetic erosion reflected in small effective population sizes and high spatial genetic structure of the analyzed populations were detected. Based on these findings, we recommend the in situ and ex situ conservation strategies for conserving and restoring the genetic resources of black poplar populations in this strongly transformed by human river valley ecosystem. [ABSTRACT FROM AUTHOR]

• The level of genetic variation was high and comparable between populations. • The genetic structure of black poplar populations was homogenous. • All examined populations experienced the demographic bottleneck in the past. • Clear signals of introgression were detected in analyzed black poplar seedlings. • The results support the need to protect the genetic resources of P. nigra in Poland. Black poplar (Populus nigra L.) is an economically and ecologically important tree species which in the past was widely distributed along riversides in vast areas of Europe. Currently, it deserves conservation with a view of serious threats resulting from the species habitat reduction and progressive introgressive hybridization. Here we examined the regeneration capacities of black poplar populations from the Vistula River in Poland in a region which has been influenced by man-made disturbance regimes. Using both nuclear (n DNA) and chloroplast (cp DNA) genetic markers and spatial location data we: (1) evaluated the susceptibility of the studied populations to introgression, (2) determined genetic diversity of the analyzed offspring and compared it with their maternal stands, and (3) assessed the level of gene flow among populations and generations. Nine hybrid individuals were identified in the examined groups of one-year poplar seedlings. Both molecular variance and clustering analyses showed that the gene pool of black poplar populations was homogenous (F ST = 0.004, p = 0.623). Heterozygosity and allelic richness were comparable between adult and their progeny populations, and there were also no strong disturbances in a random distribution of genotypes in the study area. Low spatial genetic structure was observed in two seedling groups and among all black poplar individuals from the Wysoczyn population. The results are discussed in the context of natural regeneration capacities of the remaining black poplar populations and protection of the species genetic resources along the landscapes of the river valleys. [ABSTRACT FROM AUTHOR]

Black poplar ( Populus nigra L.) is a widely distributed species that plays a crucial role in riparian forest ecosystems. Due to a reduction in its natural habitats and hybridization with introduced poplar species clones, its genetic pool is decreasing and efforts are required to preserve this species. Seeds of black poplar are short-lived and quickly lose viability during conventional storage in gene banks. Therefore, in order to preserve ex situ the genetic diversity of this species, the feasibility of seed cryopreservation in liquid nitrogen (at −196 °C, LN) for periods of 24 h and 2 years was investigated. Seeds were harvested from three individual trees (two provenances) and desiccated to different levels of water content (WC) in the range of 0.02-0.35 g g (g HO/g dry mass, g g) prior to immersion in LN. Seed germination was assessed after each treatment. P. nigra seeds tolerated desiccation to WC 0.07 g g but after severe desiccation to WC <0.05 g g exhibited a significant reduction in germination. Results indicated that all black poplar seeds, regardless of origin, year of harvesting and seed quality, could be cryopreserved for 24 h when their WC was in the range of 0.11-0.17 g g. Physiology of P. nigra seeds showed in this paper is consistent with attributes of intermediate seed storage behavior. This study provides a foundation for using cryopreservation for the ex situ conservation of P. nigra seeds. [ABSTRACT FROM AUTHOR]

Emissions of trace gases (carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC)), and volatile organic compounds (VOCs) from combustion of European beech, Pyrenean oak and black poplar in a domestic woodstove and fireplace were studied. These woods are widely used as biofuel in residential combustion in Southern and mid-European countries. VOCs in the flue gases were collected in Tedlar bags, concentrated in sorbent tubes and analysed by thermal desorption-gas chromatography–flame ionisation detection (GC–FID). CO2 emissions ranged from 1415 ± 136 to 1879 ± 29 g kg−1 (dry basis). The highest emission factors for CO and THC, 115.8 ± 11.7 and 95.6 24.7 ± 6.3 g kg−1 (dry basis), respectively, were obtained during the combustion of black poplar in the fireplace. European beech presented the lowest CO and THC emission factors for both burning appliances. Significant differences in emissions of VOCs were observed among wood species burnt and combustion devices. In general the highest emission factors were obtained from the combustion of Pyrenean oak in the woodstove. Among the VOCs identified, benzene and related compounds were always the most abundant group, followed by oxygenated compounds and aliphatic hydrocarbons. The amount and the composition of emitted VOCs were strongly affected by the wood composition, the type of burning device and operating conditions. Emission data obtained in this work are useful for modelling the impact of residential wood combustion on air quality and tropospheric ozone formation. [ABSTRACT FROM AUTHOR]