Search

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Boreal forests receive nitrogen-(N)-enrichment via atmospheric deposition and industrial fertilization. While it is known that N-enrichment can intensify interactions with natural antagonists, it remains poorly understood how genetic variability in plant defense chemistry can affect biotic interactions and height growth in N-enriched environments. We grew replicates of five low- and high-tannin Populus tremula genotypes, respectively, under three N-treatments (ambient, 15, and 150 kg N ha−1 yr−1). We assessed shoot blight occurrence (i.e. symptoms caused by Venturia fungi) during four growing seasons, and tree height growth during the same period. Damage by Venturia spp. increased with N-addition during all years, likely due to enhanced foliar quality. Low–tannin plants showed higher incidences of Venturia infection than high-tannin plants, regardless of the N-input-level. Height responded to an N-by-tannin-group interaction, which occurred because high-tannin plants grew taller than low-tannin plants at the high N-treatment, but not under the other N-levels. This pattern indicates that innate resource investment into tannin production yields a positive effect on growth under N-enriched conditions. Given that N-deposition is increasing globally, our research suggests that further studies are needed to investigate how N-enrichment interacts with plant defense traits globally. Moreover, our research suggests that N-deposition may provide an advantage for well-defended, high-tannin plants; and further, that genetic diversity in plant defense may be a key mechanism by which plant populations respond to this change.

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Condensed tannin (CT) contents of European aspen (Populus tremula L.) vary among genotypes, and increases in nitrogen (N) availability generally reduce plants’ tannin production in favor of growth, through poorly understood mechanisms. We hypothesized that intrinsic tannin production rates may co-vary with gene expression responses to soil N and resource allocation within the phenylpropanoid pathway (PPP). Thus, we examined correlations between soil N levels and both expression patterns of eight PPP genes (measured by quantitative-reverse transcription PCR) and foliar phenolic compounds (measured by liquid chromatography–mass spectrometry) in young aspen genets with intrinsically extreme CT levels. Monitored phenolics included salicinoids, lignins, flavones, flavonols, CT precursors and CTs. The PPP genes were consistently expressed more strongly in high-CT trees. Low N supplements reduced expression of genes throughout the PPP in all genets, while high N doses restored expression of genes at the beginning and end of the pathway. These PPP changes were not reflected in pools of tannin precursors, but varying correlations between gene expression and foliar phenolic pools were detected in young and mature leaves, suggesting that processes linking gene expression and the resulting phenolics vary spatially and temporally. Precursor fluxes suggested that CT-related metabolic rate or sink controls are linked to intrinsic carbon allocation strategies associated with N responses. Overall, we found more negative correlations (indicative of allocation trade-offs) between PPP gene expression and phenolic products following N additions in low-CT plants than in high-CT plants. The tannin-related expression dynamics suggest that, in addition to defense, relative tannin levels may also be indicative of intraspecific variations in the way aspen genets respond to soil fertility.

Small samples from European aspen (Populus tremula L.) were impregnated with carbohydrates oxidized by Fenton's reagent using water in a vacuum, followed by heating in an oven at 103 °C. An antiswelling efficiency (ASE) of around 45% for wood treated with oxidized glucose and 35% for wood treated with oxidized sucrose was obtained. Samples treated with oxidized carbohydrates gave water repellent effectiveness (WRE) values over 35%. The decrease in cell wall thickness during impregnation was about 18% less in the presence of oxidized glucose than samples only treated with Fenton's reagent. An ASE of 20% for the wood samples that had been treated with oxidized glucose was obtained after 7 days of soaking in water. The reasons for the improvement in dimensional stability are discussed in this work.

The impact of drying on the structure of the never-dried hardwood cell wall was studied at nanometer level by means of wide- and small-angle X-ray scattering (WAXS, SAXS), and at micrometer level by X-ray microtomography (mu CT). Never-dried silver birch, European aspen and hybrid aspen samples were measured by WAXS in situ during drying in air. The samples included juvenile and mature wood, as well as normal and tension wood to allow comparison of the effects of different matrix compositions and microfibril angles. The deformations of cellulose crystallites and amorphous components of the cell wall were detected as changes in the cellulose reflections 200 and 004 and amorphous halo in the WAXS patterns. Especially, the width of the reflection 004, corresponding to the cellulose chain direction, increased due to drying in all the samples, indicating an increase of strain and disorder of the chains. Also, the cellulose unit cell shrank 0.2-0.3% during drying in this direction in all the samples except in hybrid aspen tension wood. According to the SAXS results of silver birch, the distance between microfibrils decreased during drying. It was detected by mu CT that the mean cross-sectional maximum width of the parenchymatous rays decreased from that of never-dried to air-dried birch by roughly 16%., QC 20120102

Rostsvampen knäckesjuka (Melampsora pinitorqua) är en allvarlig skadegörare i tallungskogar i Sverige. Svampen värdväxlar mellan inhemsk tall (Pinus sylvestris) och asp (Populus tremula). De tydligaste symptomen är böjda eller avbrutna skott i de övre grenvarven i tallarnas krona. Detta kan resultera i reducerad tillväxt och försämrad timmerkvalitet. Väl medvetna om riskerna med knäckesjuka har skogsägare i Sverige under lång tid kämpat med att utrota aspen både i tallföryngringar och i plantskolor. Nuförtiden har attityden gentemot asp förändrats i och med att naturvård implementerats i skogsskötseln i högre grad. Detta har resulterat i en ökning av antalet aspar som lämnas kvar i naturvårdssyfte på föryngringsytorna. Syftet med studien var att utvärdera betydelsen av kvarlämnade naturvärdesträd av asp, jämfört med självföryngrat aspsly, som spridningskälla för knäckesjuka i unga tallbestånd. Huvudhypotesen var att löv från aspsly utgör en större smittokälla än löv från vuxna aspar. Fältstudien utfördes i Västerbottens län. Elva tallungskogar mellan 5-15 år valdes slumpmässigt ut bland bestånd infekterade av knäckesjuka samt innehållande naturvärdesaspar. Förekomst och omfattning av årets angrepp av knäckesjuka registrerades för varje träd inom 18 GPS märkta provytor i varje bestånd. Även antalet rotskott av asp räknades på provytorna. Samtliga stora aspar i bestånden registrerades med GPS för analys av avstånd mellan aspar och provytorna. Resultatet påvisade en högst signifikant korrelation mellan antalet rotskott av asp och infektionsgraden på de unga tallarna. Ingen av de två variablerna avstånd till närmsta stora asp eller antalet stora aspar inom 100 m från provytorna var signifikant korrelerade med infektionsgraden på tallarna. Aspträdens roll i spridningen av knäckesjuka verkade först och främst vara att skjuta rotskott. Det var en signifikant positiv korrelation mellan tallens toppskottslängd och angreppsgraden av knäckesjuka. Välväxande tallar föreföll mer, Pine twisting rust (Melampsora pinitorqua) is a serious fungal pathogen that in Sweden infects young Scots pine (Pinus sylvestris) stands and has European aspen (Populus tremula) as alternate host. Pine twisting rust (PTR) infects the pine’s annual shoots. Main symptoms are bent or broken shoots in the upper crown of young Scots pines which can result in reduced growth and timber quality. Well aware of the risk of PTR Swedish foresters has fought to eliminate aspen, both in Scots pine regenerations and in nurseries. Today, the attitude towards aspen trees has changed with the increased implementation of environmental consideration in Swedish forest management. This has resulted in an increased number of mature aspens retained for conservation purposes in pine regenerations. The aim of this study was to evaluate the importance of mature aspen trees compared to young aspen sprouts as causal agents of PTR in young Scots pine stands. The main hypothesis was that leaves of aspen sprouts carry more infection compared to leaves on mature aspen trees. The field study took place in the county of Västerbotten in northern Sweden and eleven 5-15-year-old Scots pine stands were randomly chosen for the study based the occurrence of PTR and large aspen trees. The occurrence and severity of current-year PTR infection on each pine was registered within 18 GPS-positioned sample plots per stand. Also the number of aspen sprouts was counted. Furthermore, all large aspen trees growing in the stand were GPS-positioned. The result showed a highly significant correlation between the number of aspen sprouts and infection rate on Scots pine saplings. None of the two variables concerning the distance- or the numbers of large aspen were significantly correlated to PTR infection rate. It appeared that the adult aspen’s role in the spread of PTR was primarily by producing aspen sprouts. There was a significant positive correlation between leader length and PTR infection rate and hence, productiv

Knäckesjuka (Melampsora pinitorqua) är en rostsvamp som orsakar skador på plantor och unga träd av tall (Pinus sylvestris) i Sverige, vilket lokalt kan innebära stora problem. Svampen har en komplicerad livscykel som innefattar en värdväxling mellan tall och asp (Populus sp.). Syftet med studien var att undersöka om sporer av knäckesjukasvampen är lika vanligt förekommande på hybridasp (Populus tremula x tremuloides) som på europeisk asp (Populus tremula). Med tanke på att hybridasp kan komma att bli ett alternativ som biomassaproducent är det viktigt att studera tänkbara risker detta trädslag kan föra med sig. Min hypotes var att hybridaspen är mer resistent än europeisk asp mot knäckesjuka, och att den därmed också sprider mindre mängd sporer som i sin tur kan infektera tall. Genom att inventera 12 hybridaspplanteringar etablerade åren 2005-2007 i Jämtland och Västernorrland och jämföra sporförekomsten på blad av hybridasp med blad på rotskott av europeisk asp på samma lokaler, samlades data in för att kunna testa denna hypotes. Signifikanta skillnader kunde ses mellan hybridaspen och den europeiska aspen på samtliga 12 lokaler. Totalt var endast 1 % av hybridaspens löv infekterade jämfört med 35 % av den europeiska aspens löv. Studien kompletterades med en inventering av tre hybridaspplanteringar etablerade i Västerbotten 1993, för att se om knäckesjuka förekommer även på äldre träd. Här var 3-6 % av hybridasplöven infekterade. Slutsatsen blev att knäckesjuka kan infektera även hybridasp, men att infektionsgraden är mycket låg i jämförelse med europeisk asp. Denna slutsats styrks av liknande resultat i tidigare studier. Eventuellt kan detta resultat öka motivationen för plantering av hybridasp. De skogsbrukare som tvekat inför hybridasp, på grund av smittorisken till närliggande tallföryngringar, kan med stöd av denna studie känna större tilltro till detta snabbväxande trädslag. Abstract (eng) Pine twisting rust (Melampsora pinitorqua) is a rust fungus that cause, Pine twisting rust (Melampsora pinitorqua) is a rust fungus that causes damage in plantations and young stands of Scots pine (Pinus sylvestris) in Sweden, which can cause extensive problem on a local scale. The fungus has a complicated life-cycle which involves two host species, Scots pine and European aspen (Populus tremula). The purpose of this study was to examine whether the pine twisting rust is as common on hybrid aspen (Populus tremula x tremuloides) as on European aspen. Considering that hybrid aspen likely will become an alternative for biomass production, it is important to know which risks it might bring. My hypothesis was that the hybrid aspen is more resistant to pine twisting rust than the European aspen, and therefore it will spread a less amount of spores that can infect pine. By measuring infection on 12 hybrid aspen plantations established in 2005-2007 in Jämtland and Västernorrland, and comparing the amount of uredospores on hybrid aspen leaves with leaves on suckers of European aspen at the same sites, data was collected to test the stated hypothesis. Significant differences were found between the hybrid aspen and the European aspen on all 12 sites. Only 1% of the leaves on the hybrid aspens were infected compared to 35% of the leaves on the European aspens. The study was complemented with an inventory of three hybrid aspen plantations established in Västerbotten in 1993, to conclude if spores of the rust were present on older trees as well. On these sites, 3-6% of the leaves were infected. The conclusion was that pine twisting rust can infect hybrid aspen, but the rate of disease incidence is very low compared to European aspen. This conclusion is also supported by similar results in earlier studies. Perhaps these results increase the possibilities for future planting of hybrid aspen. The forest owners that have hesitated to plant hybrid aspen, because of the risk of rust infection spreading to Scots pine regenerations, might with support of the