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In species with large and complex genomes such as conifers, dense linkage maps are a useful resource for supporting genome assembly and laying the genomic groundwork at the structural, populational, and functional levels. However, most of the 600+ extant conifer species still lack extensive genotyping resources, which hampers the development of high-density linkage maps. In this study, we developed a linkage map relying on 21,570 single nucleotide polymorphism (SNP) markers in Sitka spruce (Picea sitchensis [Bong.] Carr.), a long-lived conifer from western North America that is widely planted for productive forestry in the British Isles. We used a single-step mapping approach to efficiently combine RAD-seq and genotyping array SNP data for 528 individuals from 2 full-sib families. As expected for spruce taxa, the saturated map contained 12 linkages groups with a total length of 2,142 cM. The positioning of 5,414 unique gene coding sequences allowed us to compare our map with that of other Pinaceae species, which provided evidence for high levels of synteny and gene order conservation in this family. We then developed an integrated map for P. sitchensis and Picea glauca based on 27,052 markers and 11,609 gene sequences. Altogether, these 2 linkage maps, the accompanying catalog of 286,159 SNPs and the genotyping chip developed, herein, open new perspectives for a variety of fundamental and more applied research objectives, such as for the improvement of spruce genome assemblies, or for marker-assisted sustainable management of genetic resources in Sitka spruce and related species. [ABSTRACT FROM AUTHOR]

Conifers growing in temperate forests utilize sustained forms of thermal dissipation during winter to protect the photosynthetic apparatus from damage, which can be monitored via pronounced reductions in photochemical efficiency (F v/ F m) during winter. Eastern white pine (Pinus strobus L.) and white spruce (Picea   glauca (Moench) Voss) are known to recover from winter stress at different rates, with pine recovering more slowly than spruce, suggesting different mechanisms for sustained dissipation in these species. Our objectives were to monitor pine and spruce throughout spring recovery in order to provide insights into key mechanisms for sustained dissipation in both species. We measured chlorophyll fluorescence, pigments, and abundance and phosphorylation status of key photosynthetic proteins. We found that both species rely on two forms of sustained dissipation involving retention of high amounts of antheraxanthin (A) + zeaxanthin (Z), one that is very slowly reversible and temperature independent and one that is more dynamic and occurs only on subzero days. Differences in protein abundance suggest that spruce, but not pine, likely upregulates cyclic or alternative pathways of electron transport involving the cytochrome b6f complex and photosystem I (PSI). Both species show an increased sustained phosphorylation of the D1 protein on subzero days, and spruce additionally shows dramatic increases in the sustained phosphorylation of light-harvesting complex II (LHCII) and other PSII core proteins on subzero days only, suggesting that a mechanism of sustained dissipation that is temperature dependent requires sustained phosphorylation of photosynthetic proteins in spruce, possibly allowing for direct energy transfer from PSII to PSI as a mechanism of photoprotection. The data suggest differences in strategy among conifers in mechanisms of sustained thermal dissipation in response to winter stress. Additionally, the flexible induction of sustained A + Z and phosphorylation of photosynthetic proteins in response to subzero temperatures during spring recovery seem to be important in providing photoprotection during transitional periods with high temperature fluctuation. [ABSTRACT FROM AUTHOR]

The European spruce bark beetle Ips typographus and the North American spruce beetle Dendroctonus rufipennis cause high mortality of spruces on their native continents. Both species have been inadvertently transported beyond their native ranges. With similar climates and the presence of congeneric spruce hosts in Europe and North America, there is a risk that one or both bark beetle species become established into the non-native continent. There are many challenges that an introduced population of bark beetles would face, but an important prerequisite for establishment is the presence of suitable host trees. We tested the suitability of non-native versus native hosts by exposing cut bolts of Norway spruce (Picea abies), black spruce (Picea mariana) and white spruce (Picea glauca) to beetle attacks in the field in Norway and Canada. We quantified attack density, brood density and reproductive success of I. typographus and D. rufipennis in the three host species. We found that I. typographus attacked white and black spruce at comparable densities to its native host, Norway spruce, and with similar reproductive success in all three host species. In contrast, D. rufipennis strongly preferred to attack white spruce (a native host) but performed better in the novel Norway spruce host than it did in black spruce, a suboptimal native host. Our results suggest that I. typographus will find abundant and highly suitable hosts in North America, while D. rufipennis in Europe may experience reduced reproductive success in Norway spruce. [ABSTRACT FROM AUTHOR]

Commercial production of high-quality lumber for Nordic conifers is negatively impacted by long rotation age and adverse negative correlations between growth and wood quality traits. A prospective solution to ensure sufficient fibre quality from future plantations is to identify key wood traits for desired applications and to consider them in tree breeding programs. In this study, we used the widespread and largely reforested white spruce (Picea glauca [Moench] Voss) in Canada to investigate the genetic control of wood flexural properties such as stiffness, i.e. modulus of elasticity (MOE), and strength, i.e. modulus of rupture (MOR). We also looked at their phenotypic and genetic correlations with other wood quality and growth traits to assess the efficiency of indirect methods of selection to improve wood flexural properties in the context of multi-trait selection in tree breeding programs. To achieve this, standardized solid wood samples, growth records and standing tree wood quality traits were collected from 289 trees belonging to 38 white spruce families from a polycross genetic trial established on two different sites in the province of Quebec, Canada. Flexural stiffness and strength, height, diameter at breast height (DBH) and wood density showed moderate to high heritability. Flexural stiffness was also positively correlated at the genetic level with flexural strength, average wood density and acoustic velocity as an indirect measure of dynamic MOE (⁠|${r}_{\mathrm{G}}$|  = 0.99, |${r}_{\mathrm{G}}$|  = 0.78 and |${r}_{\mathrm{G}}$| = 0.78, respectively). When selecting the top 5 per cent of the trees, the expected genetic gains varied from 3.6 per cent for acoustic velocity to 16.5 per cent for MOE. Selection based on wood density and acoustic velocity would result in considerable genetic gains in flexural stiffness. Several multi-trait selection scenarios were tested to investigate the genetic gains obtained from selecting with different combinations of growth and wood quality traits. The results showed that indirect selection for wood flexural properties by means of acoustic velocity and wood density are efficient methods that can be combined in operational white spruce breeding programs to increase simultaneously genetic gains for growth and wood flexural properties. [ABSTRACT FROM AUTHOR]

Conifer breeding programmes are increasingly selecting for wood quality in addition to growth so to ensure a sufficient flow of high-quality fibre from future forest plantations. As wood density is one of the most frequently used indicators of wood quality, there is a growing interest to consider this trait in selection, and thus enhance the properties of end-use products from planted trees. However, wood density varies at different scales within trees, with pith-to-bark patterns and year-to-year fluctuations representing two important sources of variation. From both physiological and end-use points of view, it is desirable to produce stems with limited pith-to-bark and year-to-year wood density variation. In the present study, we assessed patterns of pith-to-bark and year-to-year variation in 2196 wood density patterns and evaluated the genetic control of traits characterizing this variation. The experimental data came from a 15-year-old white spruce genetic trial representing 93 full-sib families replicated in two contrasting environments in Quebec, Canada. To separate pith-to-bark from year-to-year variation, non-linear models were developed to describe pith-to-bark patterns of variation in the mean ring density (MRD) of individual trees as well as for latewood density (LWD) and latewood proportion. We observed that pith-to-bark variation was more under genetic control than year-to-year variation, for which only LWD and proportion of latewood width to overall ring width reached moderate genetic control. Little genotype-by-environment interaction was observed although wood density patterns differed significantly between sites. The present approach could help identify trees or families that tend to have limited pith-to-bark and year-to-year variation in wood density as part of tree genetic improvement programmes to provide future trees with more uniform and desirable wood attributes. [ABSTRACT FROM AUTHOR]

In an attempt to comprehensively study the dynamics of non-structural carbon compounds (NCCs), we measured the seasonal changes of soluble sugars, starch, lipids and sugar alcohols in the leaves, branches, stem and roots of the fast-growing Pinus contorta (Loudon) (pine) and slow-growing Picea glauca (Moench) Voss (spruce) trees growing in a boreal climate. In addition to measuring the seasonal concentrations of these compounds, the relative contribution of these compounds to the total NCC pool within the organs of trees (~8 m tall) was estimated and compared across different phenological and growth stages. Both species showed large seasonal shifts from starch to sugars from spring to fall in nearly all organs and tissues; most likely an adaptation to the cold winters. For both species, the total fluctuation of sugar + starch across the year (i.e. the difference between the minimum and maximum observed across collection times) was estimated to be between 1.6 and 1.8 kg for all NCCs. The fluctuation, however, was 1.40 times greater than the minimum reserves in pine, while only 0.72 times the minimum reserves in spruce. By tissue type, NCC fluctuations were greatest in the roots of both species. Roots showed a large build-up of reserves in late spring, but these reserves were depleted over summer and fall. Storage reserves in needles and branches declined over the summer, and this decline may be linked to the sink strength of the stem during diameter growth. Some notable highlights of this holistic study: a late winter build-up of sugars in the stem xylem of both species, but especially spruce; and an increase in sugar alcohols in the bark of spruce in very late winter, which could indicate mobilization to support early growth in spring and high lipid reserves in the bark of pine, which appeared not to be impacted by seasonal changes between summer and winter. Collectively, these observations point toward a more conservative NCC reserve strategy in spruce compared with pine, which is consistent with its stress tolerance and greater longevity. [ABSTRACT FROM AUTHOR]

In the face of anticipated climate change, growth models require modifications to effectively model likely future growth and survival of trees and stands. To support incorporation of climate effects in the Mixedwood Growth Model (MGM), we developed climate-sensitive mixed effects models for lodgepole pine (Pinus contorta Douglas ex Loudon), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), balsam poplar (Populus balsamifera L.) and white spruce (Picea glauca (Moench) Voss), and examined how tree size, intra- and interspecific competition and climate will influence individual-tree diameter growth. Remeasurement data from permanent growth and yield sample plots from across the western Canadian boreal forest were used for this study. Based on the model that we developed, tree size, competition and climate had varying effects on growth, among tree species. Although intraspecific competition had a stronger negative effect on growth for deciduous and white spruce trees, interspecific competition had a stronger negative effect on the growth of pine. Deciduous trees growing in stands having longer frost-free period experienced an increase in growth but a negative effect of frost-free period was observed for conifers. In addition, higher moisture was found to increase tree growth, but the influence of available moisture on growth was dependent on competition. Overall, these results suggest that, under climate warming, between-species differences in growth responses will contribute to our understanding of the stand dynamics in the western boreal region of Canada. Climate sensitive growth models developed in this study will be useful in the recalibration of MGM and other individual-tree models, and predictions will contribute to better-informed decisions about silvicultural treatments for these economically important boreal tree species. [ABSTRACT FROM AUTHOR]

Aims Black spruce (Picea mariana [Mill.] B.S.P.) and white spruce (Picea glauca [Moench] Voss.) are congeneric species. Both are moderately shade tolerant and widely distributed across North American boreal forests. Methods To understand light effects on their ecophysiological responses to elevated CO2, 1-year-old seedlings were exposed to 360 µmol mol−1 and 720 µmol mol−1 CO2 at three light conditions (100%, 50% and 30% of full light in the greenhouse). Foliar gas exchanges were measured in the mid- and late-growing season. Important Findings Elevated CO2 increased net photosynthesis (P n) and photosynthetic water use efficiency, but it reduced stomatal conductance and transpiration. The stimulation of photosynthesis by elevated CO2 was greatest at 50% light and smallest at 100%. Photosynthesis, maximum carboxylation rate (V cmax) and light-saturated rate of electron transport (J max) all decreased with decreasing light. Elevated CO2 significantly reduced V cmax across all light treatments and both species in mid-growing season. However, the effect of elevated CO2 became insignificant at 30% light later in the growing season, with the response being greater in black spruce than in white spruce. Elevated CO2 also reduced J max in white spruce in both measurements while the effect became insignificant at 30% light later in the growing season. However, the effect on black spruce varied with time. Elevated CO2 reduced J max in black spruce in mid-growing season in all light treatments and the effect became insignificant at 30% light later in the growing season, while it increased J max later in the season at 100% and 50% light. These results suggest that both species benefited from elevated CO2, and that the responses varied with light supply, such that the response was primarily physiological at 100% and 50% light, while it was primarily morphological at 30% light. [ABSTRACT FROM AUTHOR]

Nine open-pollinated families of Picea glauca (Moench) Voss from the Region D1 Controlled Parentage Program (Alberta, Canada) were systematically chosen from fast, medium and slow-growth rankings based on breeding values for height from field progeny tests at age 30 years. Seeds from these families were sown and grown to age 3 years to analyze the performance and correlations of growth, physiological traits and expression of gibberellin-related genes, with and without elevated gibberellic acid 3 (GA3) application, under greenhouse conditions. We observed a significant interaction effect between families and growth groups subjected to 50 μg μl−1 of GA3 treatment, causing a decrease in apical internode length, diameter, volume and absolute transcript level for fast-growing families but an increase for families in the slow-growth group for the same traits. We also observed that in the apical internode, the gene PgGA20ox1 had significantly more relative expression under the elevated GA3 treatment than the control trees. In the stem, PgGA3ox1 showed a significantly higher relative expression under elevated GA3 treatment compared with control trees. Also, the slow-growth group showed more relative expression of PgGA20ox1 (in the apical internode) and PgGA3ox1 (in the stem) than the fast-growth group. The apical internode length and diameter significantly increased by 24% and 16%, respectively, with the hormone treatment in the slow growing group. In general, the PgGID1 and PgDELLA1 genes were upregulated and downregulated respectively, in spruce shoots under the GA3 treatment, meaning a positive feedback regulation by those genes were influencing PgGA20ox1 and PgGA3ox1 expression in that tissue type. Moreover, there was a significant correlation between absolute transcript levels of PgGA20ox1 in the apical internode and apical internode length, and absolute transcript levels of PgGA3ox1 in the stem and the diameter, in the fast-growth group families. This study shows that expression of GA genes is a limiting factor for growth in certain white spruce families with a complex feedback mechanism. Finally, absolute transcript levels of endogenous GA relative to growth parameters in juvenile seedlings could potentially be used to accelerate the early selection of families with inherently rapid apical and radial growth expansion. [ABSTRACT FROM AUTHOR]

The intensity of extreme heat and drought events has drastically risen in recent decades and will likely continue throughout the century. Northern forests have already seen increases in tree mortality and a lack of new recruitment, which is partially attributed to these extreme events. Boreal species, such as paper birch (Betula papyrifera) and white spruce (Picea glauca), appear to be more sensitive to these changes than lower-latitude species. Our objectives were to investigate the effects of repeated heatwaves and drought on young paper birch and white spruce trees by examining (i) responses in leaf gas exchange and plant growth and (ii) thermal acclimation of photosynthetic and respiratory traits to compare ecophysiological responses of two co-occurring, yet functionally dissimilar species. To address these objectives, we subjected greenhouse-grown seedlings to two consecutive summers of three 8-day long, +10 °C heatwaves in elevated atmospheric CO2 conditions with and without water restriction. The data show that heatwave stress reduced net photosynthesis, stomatal conductance and growth—more severely so when combined with drought. Acclimation of both photosynthesis and respiration did not occur in either species. The combination of heat and drought stress had a similar total effect on both species, but each species adjusted traits differently to the combined stress. Birch experienced greater declines in gas exchange across both years and showed moderate respiratory but not photosynthetic acclimation to heatwaves. In spruce, heatwave stress reduced the increase in basal area in both experimental years and had a minor effect on photosynthetic acclimation. The data suggest these species lack the ability to physiologically adjust to extreme heat events, which may limit their future distributions, thereby altering the composition of boreal forests. [ABSTRACT FROM AUTHOR]

In 2008, a thinning trial consisting in the removal of competitors around high growth potential stems (crop trees, CTs) was initiated as the first step of a structural conversion to transform even-aged stands into uneven-aged stands. Two intensities of thinning by CT release and thinning from below were tested in white spruce (Picea glauca [Moench] Voss) plantations and in balsam fir (Abies balsamea [L.] Mill)—dominated naturally regenerated stands. Unlike thinning from below, which aims to remove poor quality stems to improve the growth of residual trees, thinning by CT release aims to reduce competition between dominant trees. Trees thinned by CT release showed a significantly higher diameter at breast height increment than those in the control plots. CT release did not significantly increase stand structure, nor did it reduce stand growth, which helps to address the concerns of regional forest stakeholders. CT release may offer other benefits in the long term, but subsequent interventions are necessary to evaluate if this treatment meets the desired objectives. [ABSTRACT FROM AUTHOR]

Plant mitochondrial genomes vary widely in size. Although many plant mitochondrial genomes have been sequenced and assembled, the vast majority are of angiosperms, and few are of gymnosperms. Most plant mitochondrial genomes are smaller than a megabase, with a few notable exceptions. We have sequenced and assembled the complete 5.5-Mb mitochondrial genome of Sitka spruce (Picea sitchensis), to date, one of the largest mitochondrial genomes of a gymnosperm. We sequenced the whole genome using Oxford Nanopore MinION, and then identified contigs of mitochondrial origin assembled from these long reads based on sequence homology to the white spruce mitochondrial genome. The assembly graph shows a multipartite genome structure, composed of one smaller 168-kb circular segment of DNA, and a larger 5.4-Mb single component with a branching structure. The assembly graph gives insight into a putative complex physical genome structure, and its branching points may represent active sites of recombination. [ABSTRACT FROM AUTHOR]

With current trends in global warming, it has been suggested that spruce budworm outbreaks may spread to northern parts of the boreal forest. However, the major constraints for a northward expansion are the availability of suitable host trees and the insect winter survival capacity. This study aimed to determine the effect of larval feeding on balsam fir, white spruce and black spruce on various spruce budworm life history traits of both the parental and the progeny generations. Results indicated that the weight of the overwintering larval progeny and their winter survival were influenced by host tree species on which larvae of the parental generation fed. White spruce was the most suitable host for the spruce budworm, producing the heaviest pupae and the heaviest overwintering larvae while black spruce was the least suitable, producing the smallest pupae and the smallest overwintering progeny. Overwintering larvae produced by parents that fed on black spruce also suffered higher winter mortality than individuals coming from parents that fed on balsam fir or white spruce. With current trends in global warming, spruce budworm is expected to expand its range to northern boreal forests where black spruce is the dominant tree species. Such northern range expansion might not result in outbreaks if low offspring winter survival on black spruce persist. [ABSTRACT FROM AUTHOR]

White spruce breeding has traditionally focused on genetic improvement for high productivity, targeting mostly stem volume. However, new challenges, such as the effects of climate change on individual trees and ecosystems and the changing nature of forest products markets, require action to address these issues while providing improved stock for seed and seedling production. This work aims to define the relative importance of white spruce wood traits for the lumber industry, with the intent of guiding tree breeding programs. This manuscript examines: (1) wood features that are important for lumber, (2) the genetics of wood traits and their improvement and (3) the level of acceptance of raw material with optimal traits, as obtained from a survey conducted with sawmills. Stem diameter at stump height, wood density, bending strength and stiffness were determined as the most important properties for sawmills. Decay proportion, knot diameter, slope of grain and the proportion of compression wood were also determined as important for sawmills, but to a lesser extent. Breeding efforts aiming to produce lumber should focus on stems with improved growth that are capable of sustaining the production of dense wood in greater proportion. [ABSTRACT FROM AUTHOR]

Genomics-assisted tree breeding (GATB) is an emerging biotechnology method that has the potential to produce improved planting stock in selected traits, such as greater volume or higher wood quality, more quickly and effectively compared with traditional field-based breeding (TB) methods. In this study, we conducted an ex-ante stand-level financial benefit-cost analysis that is linked to a provincial tree growth and yield projection model to investigate the potential financial benefits of using improved white spruce (Picea glauca (Moench) Voss) and lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) planting stock identified via alternative tree improvement strategies (i.e. GATB vs. TB methods) for forest companies in the province of Alberta, Canada. With consideration of major tree breeding and establishment costs, expected sawlog price premiums at harvest, a shorter breeding cycle time, and additional genetic gain in volume achieved from using the GATB method relative to the TB method in the financial analysis; this study found that the use of GATB-selected third-generation planting stock was difficult to justify economically alone compared with TB-selected seedlings under the current sawlog market value and the current planting rate with improved stock in the province. However, results of our sensitivity analysis also revealed that the GATB method is: (1) more financially supported at lower discount rates; (2) strongly supported through decreased seedling costs with increased areas planted with improved stock; and (3) strongly supported through an increase in log price premiums at harvest resulting from potentially better wood quality and higher volume production relative to TB-selected stock. The findings of this study highlight several important market and biophysical factors that forest managers should take into account when adopting biotechnology in forestry. [ABSTRACT FROM AUTHOR]

Motivation In the modern genomics era, genome sequence assemblies are routine practice. However, depending on the methodology, resulting drafts may contain considerable base errors. Although utilities exist for genome base polishing, they work best with high read coverage and do not scale well. We developed ntEdit, a Bloom filter-based genome sequence editing utility that scales to large mammalian and conifer genomes. Results We first tested ntEdit and the state-of-the-art assembly improvement tools GATK, Pilon and Racon on controlled Escherichia coli and Caenorhabditis elegans sequence data. Generally, ntEdit performs well at low sequence depths (<20×), fixing the majority (>97%) of base substitutions and indels, and its performance is largely constant with increased coverage. In all experiments conducted using a single CPU, the ntEdit pipeline executed in <14 s and <3 m, on average, on E.coli and C.elegans , respectively. We performed similar benchmarks on a sub-20× coverage human genome sequence dataset, inspecting accuracy and resource usage in editing chromosomes 1 and 21, and whole genome. ntEdit scaled linearly, executing in 30–40 m on those sequences. We show how ntEdit ran in <2 h 20 m to improve upon long and linked read human genome assemblies of NA12878, using high-coverage (54×) Illumina sequence data from the same individual, fixing frame shifts in coding sequences. We also generated 17-fold coverage spruce sequence data from haploid sequence sources (seed megagametophyte), and used it to edit our pseudo haploid assemblies of the 20 Gb interior and white spruce genomes in <4 and <5 h, respectively, making roughly 50M edits at a (substitution+indel) rate of 0.0024. Availability and implementation https://github.com/bcgsc/ntedit Supplementary information Supplementary data are available at Bioinformatics online. [ABSTRACT FROM AUTHOR]

Temperatures are expected to increase over the next century in all terrestrial biomes and particularly in boreal forests, where drought-induced mortality has been predicted to rise. Genomics research is helping to develop hypotheses regarding the molecular basis of drought tolerance and recent work proposed that the osmo-protecting dehydrin proteins have undergone a cladespecific expansion in the Pinaceae, a major group of conifer trees. The objectives of this study were to identify all of the putative members of the gene family, trace their evolutionary origin, examine their structural diversity and test for drought-responsive expression. We identified 41 complete dehydrin coding sequences in Picea glauca, which is four times more than most angiosperms studied to date, and more than in pines. Phylogenetic reconstructions indicated that the family has undergone an expansion in conifers, with parallel evolution implicating the sporadic resurgence of certain amino acid sequence motifs, and a major duplication giving rise to a clade specific to the Pinaceae. A variety of plant dehydrin structures were identified with variable numbers of the A-, E-, S- and K-segments and an N-terminal (N1) amino acid motif including assemblages specific to conifers. The expression of several of the spruce dehydrins was tissue preferential under non-stressful conditions or responded to water stress after 7-18 days without watering, reflecting changes in osmotic potential. We found that dehydrins with N1 K2 and N1 AESK2 sequences were the most responsive to the lack of water. Together, the family expansion, drought-responsive expression and structural diversification involving loss and gain of amino acid motifs suggests that subfunctionalization has driven the diversification seen among dehydrin gene duplicates. Our findings clearly indicate that dehydrins represent a large family of candidate genes for drought tolerance in spruces and in other Pinaceae that may underpin adaptability in spatially and temporally variable environments. [ABSTRACT FROM AUTHOR]

Maximization of genetic gain in forest tree breeding programs is contingent on the accuracy of the predicted breeding values and precision of the estimated genetic parameters. We investigated the effect of the combined use of contemporary pedigree information and genomic relatedness estimates on the accuracy of predicted breeding values and precision of estimated genetic parameters as well as rankings of selection candidates using single-step genomic evaluation (HBLUP). In this study, two traits with diverse heritabilities (tree height and wood density) were assessed at various levels of family genotyping efforts (0, 25, 50, 75, 100%) from a population of white spruce (Picea glauca) consisting of 1,694 trees from 214 open-pollinated families, representing 43 provenances in Québec, Canada. The results revealed that HBLUP bivariate analysis is effective in reducing the known bias in heritability estimates of open-pollinated populations, as it exposes hidden relatedness, potential pedigree errors, and inbreeding. The addition of genomic information in the analysis considerably improved the accuracy in breeding value estimates by accounting for both Mendelian sampling and historical co-ancestry that were not captured by the contemporary pedigree alone. Increasing family genotyping efforts were associated with continuous improvement in model fit, precision of genetic parameters, and breeding value accuracy. Yet, improvements were observed even at minimal genotyping effort indicating that even modest genotyping effort is effective in improving genetic evaluation. The combined utilization of both pedigree and genomic information may be a cost-effective approach to increase accuracy of breeding values in forest tree breeding programs where shallow pedigrees and testing large populations are the norm. [ABSTRACT FROM AUTHOR]

Conifers' exceptionally large genome (20-30 Gb) is scattered with 60% retrotransposon (RT) components and we have little knowledge on their origin and evolutionary implications. RTs may impede the expression of flanking genes and provide sources of the formation of novel small RNA (sRNAs) populations to constrain events of transposon (TE) proliferation/transposition. Here we show a declining expression of 24-nt-long sRNAs and low expression levels of their key processing gene, pgRTL2 (RNASE THREE LIKE 2) at seed set in Picea glauca. The sRNAs in 24-nt size class are significantly less enriched in type and read number than 21-nt sRNAs and have not been documented in other species. The architecture of MIR loci generating highly expressed 24-/21-nt sRNAs is featured by long terminal repeat-retrotransposons (LTR-RTs) in families of Ty3/Gypsy and Ty1/Copia elements. This implies that the production of sRNAs may be predominantly originated from TE fragments on chromosomes. Furthermore, a large proportion of highly expressed 24-nt sRNAs does not have predictable targets against unique genes in Picea, suggestive of their potential pathway in DNA methylation modifications on, for instance, TEs. Additionally, the classification of computationally predicted sRNAs suggests that 24-nt sRNA targets may bear particular functions inmetabolic processes while 21-nt sRNAs target genes involved inmany different biological processes. This study, therefore, directs our attention to a possible extrapolation that lacking of 24-nt sRNAs at the late conifer seed developmental phase may result in less constraints in TE activities, thus contributing to the massive expansion of genome size. [ABSTRACT FROM AUTHOR]

In Eastern Quebec, 36,000 ha of plantations will be ready for a first commercial thinning in the next few years. With the increase use of thinnings, managers are asked to also integrate the financial return of their operations into their decision process. They must thus take into consideration the quality of the harvested trees. Softwood is mainly used for commodity lumber production in Quebec, with mechanical properties being an important wood quality trait. To evaluate standing wood properties, the modulus of elasticity can be estimated nondestructively by measuring acoustic velocity. With the use of data from 94 sample plots in 48 plantations, the effects of tree size, competition, growth rate, and site index on the acoustic velocity of planted white spruce were studied. Competition was quantified using both distance-independent and distance-dependent competition indices. The various competition indices were also subdivided according to the competition type (conifer/broadleaved). The acoustic velocity was found to be proportional to tree size and inversely proportional to growth rate, site index, and competition. The distance-independent competition indices performed better, and discrimination between competition type did not improve the models. These results will help foresters evaluate tree quality before harvesting. [ABSTRACT FROM AUTHOR]

The evolutionary and genomic determinants of sequence evolution in conifers are poorly understood, and previous studies have found only limited evidence for positive selection. Using RNAseq data, we compared gene expression profiles to patterns of divergence and polymorphism in 44 seedlings of lodgepole pine (Pinus contorta) and 39 seedlings of interior spruce (Picea glauca × engelmannii) to elucidate the evolutionary forces that shape their genomes and their plastic responses to abiotic stress. We found that rapidly diverging genes tend to have greater expression divergence, lower expression levels, reduced levels of synonymous site diversity, and longer proteins than slowly diverging genes. Similar patterns were identified for the untranslated regions, but with some exceptions. We found evidence that genes with low expression levels had a larger fraction of nearly neutral sites, suggesting a primary role for negative selection in determining the association between evolutionary rate and expression level. There was limited evidence for differences in the rate of positive selection among genes with divergent versus conserved expression profiles and some evidence supporting relaxed selection in genes diverging in expression between the species. Finally, we identified a small number of genes that showed evidence of site-specific positive selection using divergence data alone. However, estimates of the proportion of sites fixed by positive selection (a) were in the range of other plant species with large effective population sizes suggesting relatively high rates of adaptive divergence among conifers. [ABSTRACT FROM AUTHOR]

* Background and Aims Trees invest in both primary (e.g. height) and secondary (e.g. diameter) growth. The trade-off between these investments varies between species and changes with the tree growing environment. To better establish this trade-off, readily available allometric exponents relating height to diameter at breast height (γh,dbh) and stem volume to diameter at breast height (αvdbh) were simultaneously studied. * Methods Allometric exponents αv,dbh and γh,dbh were obtained from 8893 individual tree stem analyses from two broadleaved species (Betula papyrifera, Populus tremuloides) and four conifers (Picea glauca, Picea mariana, Pinus banksiana, Abies balsamea) in the temperate and boreal forests of the province of Quebec, Canada. αvdbh and γh,dbh were related to tree age, stand density index (SDI), and mean temperature (TGS) and total precipitation (PGS) of the growing season. * Key Results αv,jdbh and γh,dbh were found to be invariant with PGS and positively related to SDI and TGS for all species except Pinus banksiana. The parameter values associated with SDI and TGS were of higher value for conifers than for broadleaved species. * Conclusions This suggests that conifers and broadleaved species have different growth patterns. This could be explained by their different mode of development, the conifer species having a stronger apical dominance than broadleaved species. Such results could be further considered in allocation studies to quantify future carbon stocks in managed forests. [ABSTRACT FROM AUTHOR]

The open-pollinated (OP) family testing combines the simplest known progeny evaluation and quantitative genetics analyses as candidates' offspring are assumed to represent independent half-sib families. The accuracy of genetic parameter estimates is often questioned as the assumption of "half-sibling" in OP families may often be violated. We compared the pedigree- vs. marker-based genetic models by analysing 22-yr height and 30-yr wood density for 214 white spruce [Picea glauca (Moench) Voss] OP families represented by 1694 individuals growing on one site in Quebec, Canada. Assuming half-sibling, the pedigree-based model was limited to estimating the additive genetic variances which, in turn, were grossly overestimated as they were confounded by very minor dominance and major additive-by-additive epistatic genetic variances. In contrast, the implemented genomic pairwise realized relationship models allowed the disentanglement of additive from all nonadditive factors through genetic variance decomposition. The marker-based models produced more realistic narrow-sense heritability estimates and, for the first time, allowed estimating the dominance and epistatic genetic variances from OP testing. In addition, the genomic models showed better prediction accuracies compared to pedigree models and were able to predict individual breeding values for new individuals from untested families, which was not possible using the pedigree-based model. Clearly, the use of marker-based relationship approach is effective in estimating the quantitative genetic parameters of complex traits even under simple and shallow pedigree structure. [ABSTRACT FROM AUTHOR]

The genome sequences of the plastid and mitochondrion of white spruce (Picea glauca) were assembled from whole-genome shotgun sequencing data using ABySS. The sequencing data contained reads from both the nuclear and organellar genomes, and reads of the organellar genomes were abundant in the data as each cell harbors hundreds of mitochondria and plastids. Hence, assembly of the 123-kb plastid and 5.9-Mb mitochondrial genomes were accomplished by analyzing data sets primarily representing low coverage of the nuclear genome. The assembled organellar genomes were annotated for their coding genes, ribosomal RNA, and transfer RNA. Transcript abundances of the mitochondrial genes were quantified in three developmental tissues and five mature tissues using data from RNA-seq experiments. C-to-U RNA editing was observed in the majority of mitochondrial genes, and in four genes, editing events were noted to modify ACG codons to create cryptic AUG start codons. The informatics methodology presented in this study should prove useful to assemble organellar genomes of other plant species using whole-genome shotgun sequencing data. [ABSTRACT FROM AUTHOR]

Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to non model species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome. Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs. Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources. [ABSTRACT FROM AUTHOR]

The southwestern region of the Yukon Territory of Canada has experienced an unprecedented spruce bark beetle outbreak (Dendroctonus rufipennis) and an increase in the frequency of forest fires that extend beyond historical trends and that have caused significant impacts on forest structure and composition. A Strategic Forest Management Plan (SFMP) for the Champagne and Aishihik Traditional Territory located in the southwest Yukon was implemented in 2004 in response to the spruce bark beetle (D. rufipennis) infestation and increased fire risk. The plan has recommended salvage harvesting of beetle-killed stands as a strategy to facilitate the development of a timber industry in the region and reduce the fire risk around communities. One of the objectives of the SFMP is to maintain, restore, or enhance forest regeneration, which requires an understanding of regeneration dynamics in the region. In this study, we investigated the regeneration of white spruce (Picea glauca), trembling aspen (Populus tremuloides), and balsam poplar (Populus balsamifera) and the relationship with climatic, disturbance, and edaphic factors within the region. Multivariate canonical correlation analysis was used to assess the weighted relationship between regeneration presence/absence and environmental factors, and negative binomial regression analysis was used to model regeneration abundance of white spruce, trembling aspen, and balsam poplar. We found that although regeneration of all three species responded positively to disturbance, the broadleaved species occupied disturbed plots at higher ratios than white spruce. Regeneration of broadleaved species was higher in open sites with exposed aspects, indicating a preference for warmer sites with higher solar radiation inputs. These findings support the hypothesis that if fire increased in the region with the warmer climate predicted by the Intergovernmental Panel on Climate Change, then the region will probably experience an increase in broadleaved species, leading to a more heterogeneous landscape. [ABSTRACT FROM AUTHOR]

Climate-related variations in functional traits of boreal tree species can result both from physiological acclimation and genetic adaptation of local populations to their biophysical environment. To improve our understanding and prediction of the physiological and growth responses of populations to climate change, we studied the role of climate of seed origin in determining variations in functional traits and its implications for tree improvement programs for a commonly reforested boreal conifer, white spruce (Picea glauca (Moench) Voss). We evaluated growth, root-to-shoot ratio (R/S), specific leaf area (SLA), needle nitrogen (Nmass), total non-structural carbohydrates (NSC) and photosynthetic traits of 3-year-old seedlings in a greenhouse experiment using seed from six seed orchards (SO) representing the different regions where white spruce is reforested in Québec. Height and total dry mass (TDM) were positively correlated with photosynthetic capacity (Amax), stomatal conductance (gs) and mesophyll conductance (gm). Total dry mass, but not height growth, was strongly correlated with latitude of seed origin (SO) and associated climate variables. Amax, gs, gm and more marginally, photosynthetic nitrogen-use efficiency (PNUE) were positively associated with the mean July temperature of the SO, while water use efficiency (WUE) was negatively associated. Maximum rates of carboxylation (Vcmax), maximum rates of electron transport (Jmax), SLA, Nmass, NSC and R/S showed no pattern. Our results did not demonstrate a higher Amax for northern seed orchards, although this has been previously hypothesized as an adaptation mechanism for maintaining carbon uptake in northern regions. We suggest that gs, gm, WUE and PNUE are the functional traits most associated with fine-scale geographic clines and with the degree of local adaptation of white spruce populations to their biophysical environments. These geographic patterns may reflect in situ adaptive genetic differences in photosynthetic efficiency along the cline. [ABSTRACT FROM AUTHOR]

The recent sequencing of several gymnosperm genomes has greatly facilitated studying the evolution of their genes and gene families. In this study, we examine the evidence for expression-mediated selection in the first two fully sequenced representatives of the gymnosperm plant clade (Picea abies and Picea glauca). We use genome-wide estimates of gene expression (>50,000 expressed genes) to study the relationship between gene expression, codon bias, rates of sequence divergence, protein length, and gene duplication. We found that gene expression is correlated with rates of sequence divergence and codon bias, suggesting that natural selection is acting on Picea protein-coding genes for translational efficiency. Gene expression, rates of sequence divergence, and codon bias are correlated with the size of gene families, with large multicopy gene families having, on average, a lower expression level and breadth, lower codon bias, and higher rates of sequence divergence than single-copy gene families. Tissue-specific patterns of gene expression were more common in large gene families with large gene expression divergence than in single-copy families. Recent family expansions combined with large gene expression variation in paralogs and increased rates of sequence evolution suggest that some Piceagene families are rapidly evolving to cope with biotic and abiotic stress. Our study highlights the importance of gene expression and natural selection in shaping the evolution of protein-coding genes in Picea species, and sets the ground for further studies investigating the evolution of individual gene families in gymnosperms. [ABSTRACT FROM AUTHOR]

Insights from sequenced genomes of major land plant lineages have advanced research in almost every aspect of plant biology. Until recently, however, assembled genome sequences of gymnosperms have been missing from this picture. Conifers of the pine family (Pinaceae) are a group of gymnosperms that dominate large parts of the world's forests. Despite their ecological and economic importance, conifers seemed long out of reach for complete genome sequencing, due in part to their enormous genome size (20-30 Gb) and the highly repetitive nature of their genomes. Technological advances in genome sequencing and assembly enabled the recent publication of three conifer genomes: white spruce (Picea glauca), Norway spruce (Picea abies), and loblolly pine ([Pinus taeda). These genome sequences revealed distinctive features compared with other plant genomes and may represent a window into the past of seed plant genomes. This Update highlights recent advances, remaining challenges, and opportunities in light of the publication of the first conifer and gymnosperm genomes. [ABSTRACT FROM AUTHOR]

Background and Aims MADS-box genes comprise a gene family coding for transcription factors. This gene family expanded greatly during land plant evolution such that the number of MADS-box genes ranges from one or two in green algae to around 100 in angiosperms. Given the crucial functions of MADS-box genes for nearly all aspects of plant development, the expansion of this gene family probably contributed to the increasing complexity of plants. However, the expansion of MADS-box genes during one important step of land plant evolution, namely the origin of seed plants, remains poorly understood due to the previous lack of whole-genome data for gymnosperms. Methods The newly available genome sequences of Picea abies, Picea glauca and Pinus taeda were used to identify the complete set of MADS-box genes in these conifers. In addition, MADS-box genes were identified in the growing number of transcriptomes available for gymnosperms. With these datasets, phylogenies were constructed to determine the ancestral set of MADS-box genes of seed plants and to infer the ancestral functions of these genes. Key Results Type I MADS-box genes are under-represented in gymnosperms and only a minimum of two Type I MADS-box genes have been present in the most recent common ancestor (MRCA) of seed plants. In contrast, a large number of Type II MADS-box genes were found in gymnosperms. The MRCA of extant seed plants probably possessed at least 11–14 Type II MADS-box genes. In gymnosperms two duplications of Type II MADS-box genes were found, such that the MRCA of extant gymnosperms had at least 14–16 Type II MADS-box genes. Conclusions The implied ancestral set of MADS-box genes for seed plants shows simplicity for Type I MADS-box genes and remarkable complexity for Type II MADS-box genes in terms of phylogeny and putative functions. The analysis of transcriptome data reveals that gymnosperm MADS-box genes are expressed in a great variety of tissues, indicating diverse roles of MADS-box genes for the development of gymnosperms. This study is the first that provides a comprehensive overview of MADS-box genes in conifers and thus will provide a framework for future work on MADS-box genes in seed plants. [ABSTRACT FROM AUTHOR]

Redundancy and competition between R2R3-MYB activators and repressors on common target genes has been proposed as a fine-tuning mechanism for the regulation of plant secondary metabolism. This hypothesis was tested in white spruce [Picea glauca (Moench) Voss] by investigating the effects of R2R3-MYBs from different subgroups on common targets from distinct metabolic pathways. Comparative analysis of transcript profiling data in spruces overexpressing R2R3-MYBs from loblolly pine (Pinus taeda L.), PtMYB1, PtMYB8, and PtMYB14, defined a set of common genes that display opposite regulation effects. The relationship between the closest MYB homologues and 33 putative target genes was explored by quantitative PCR expression profiling in wild-type P. glauca plants during the diurnal cycle. Significant Spearman’s correlation estimates were consistent with the proposed opposite effect of different R2R3-MYBs on several putative target genes in a time-related and tissue-preferential manner. Expression of sequences coding for 4CL, DHS2, COMT1, SHM4, and a lipase thio/esterase positively correlated with that of PgMYB1 and PgMYB8, but negatively with that of PgMYB14 and PgMYB15. Complementary electrophoretic mobility shift assay (EMSA) and transactivation assay provided experimental evidence that these different R2R3-MYBs are able to bind similar AC cis-elements in the promoter region of Pg4CL and PgDHS2 genes but have opposite effects on their expression. Competitive binding EMSA experiments showed that PgMYB8 competes more strongly than PgMYB15 for the AC-I MYB binding site in the Pg4CL promoter. Together, the results bring a new perspective to the action of R2R3-MYB proteins in the regulation of distinct but interconnecting metabolism pathways. [ABSTRACT FROM PUBLISHER]

Conceptual models of wood formation suggest that trees with large crowns produce wood with reduced mechanical properties due to enhanced auxin production, but few studies have explicitly examined the relationship between crown dimensions and wood properties. Using white spruce (Picea glauca (Moench) Voss) trees harvested from spacing and thinning trials in central Ontario, Canada, this study examines how live crown ratio influences the strength and stiffness of wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) were measured by conducting three-point bending tests on small (150 × 10 × 10 mm) defect-free samples selected from different radial positions at three heights within the stems. MOR and MOE were strongly and positively related to cambial age, and also increased slightly with sampling height. In addition, MOR showed a significant decrease with increasing live crown ratio – calculated as the ratio of crown length to tree height – in both the spacing and the thinning trials. However, MOE decreased significantly with live crown ratio only in the spacing trial, where the younger trees had a larger range of crown ratios. These results provide tentative support for models of wood formation that link wood quality with crown development, suggesting that crown metrics could be used to predict wood properties before harvest, but doing so may be problematic in mature stands that exhibit less variability in crown dimensions. [ABSTRACT FROM AUTHOR]

White spruce (Picea glauca) is a dominant conifer of the boreal forests of North America, and providing genomics resources for this commercially valuable tree will help improve forest management and conservation efforts. Sequencing and assembling the large and highly repetitive spruce genome though pushes the boundaries of the current technology. Here, we describe a whole-genome shotgun sequencing strategy using two Illumina sequencing platforms and an assembly approach using the ABySS software. We report a 20.8 giga base pairs draft genome in 4.9 million scaffolds, with a scaffold N50 of 20 356 bp. We demonstrate how recent improvements in the sequencing technology, especially increasing read lengths and paired end reads from longer fragments have a major impact on the assembly contiguity. We also note that scalable bioinformatics tools are instrumental in providing rapid draft assemblies.Availability: The Picea glauca genome sequencing and assembly data are available through NCBI (Accession#: ALWZ0100000000 PID: PRJNA83435). http://www.ncbi.nlm.nih.gov/bioproject/83435.Contact: ibirol@bcgsc.caSupplementary information: Supplementary data are available at Bioinformatics online. [ABSTRACT FROM PUBLISHER]

A 1149 bp genomic fragment corresponding to the 5' non-coding region of the PgD1 (Picea glauca Defensin 1) gene was cloned, characterized, and compared with all Arabidopsis thaliana defensin promoters. The cloned fragment was found to contain several motifs specific to defence or hormonal response, including a motif involved in the methyl jasmonate reponse, a fungal elicitor responsive element, and TC-rich repeat cis-acting element involved in defence and stress responsiveness. A functional analysis of the PgD1 promoter was performed using the uidA (GUS) reporter system in stably transformed Arabidopsis and white spruce plants. The PgD1 promoter was responsive to jasmonic acid (JA), to infection by fungus and to wounding. In transgenic spruce embryos, GUS staining was clearly restricted to the shoot apical meristem. In Arabidopsis, faint GUS coloration was observed in leaves and flowers and a strong blue colour was observed in guard cells and trichomes. Transgenic Arabidopsis plants expressing the PgD1::GUS construct were also infiltrated with the hemibiotrophic pathogen Pseudomonas syringae pv. tomato DC3000. It caused a suppression of defensin expression probably resulting from the antagonistic relationship between the pathogen-stimulated salicylic acid pathway and the jasmonic acid pathway. It is therefore concluded that the PgD1 promoter fragment cloned appears to contain most if not all the elements for proper PgD1 expression and that these elements are also recognized in Arabidopsis despite the phylogenetic and evolutionary differences that separates them. [ABSTRACT FROM PUBLISHER]

Chitinase genes isolated from plants, bacteria or fungi have been widely used in genetic engineering to enhance the resistance of crops and trees to fungal pathogens. However, there are concerns about the possible effect of chitinase-transformed plants on nontarget fungi. This study aimed at evaluating the impact of endochitinase-transformed white spruce on soil fungal communities. Endochitinase-expressing white spruce and untransformed controls were transplanted in soils from two natural forests and grown for 8 months in a greenhouse. Soil fungal biomass and diversity, estimated through species richness and Shannon and Rao diversity indices, were not different between transgenic and control tree rhizospheres. The fungal phylogenetic community structure was the same in soil samples from control and transgenic white spruces after 8 months. Soil type and presence of seedlings had a much more significant impact on fungal community structure than the insertion and expression of the ech42 transgene within the white spruce genome. The results suggest that the insertion and constitutive expression of the ech42 gene in white spruce did not significantly affect soil fungal biomass, diversity and community structure. [ABSTRACT FROM AUTHOR]

Although a recent study of white spruce using chloroplast DNA uncovered the presence of a glacial refuge in Alaska, chloroplast failed to provide information on the number or specific localities of refugia. Recent studies have demonstrated the utility of nuclear microsatellites to refine insights into postglacial histories. The greater relative rate of mutation may allow finer scale resolution of historic dynamics, including the number, location, and sizes of refugia. Genetic data were acquired from screening 6 microsatellite loci on approximately 14 trees from each of 22 populations located across the central and western boreal forests of Canada and Alaska. Our studies combining microsatellites with Bayesian analyses of population structure in white spruce support the phylogeographic patterns uncovered using chloroplast, separating Alaskan from non-Alaskan regions. Results also support the idea that north-central Alaska served as a glacial refugium during the last glacial maximum. Additionally, the relationship between the degree of genetic differentiation and geographic distance indicated that gene flow played a more important role in structuring non-Alaskan populations, whereas drift played a more important role in structuring Alaskan populations (RST’s for non-Alaskan populations 0.029 ± 0.007 and 0.083 ± 0.012 for Alaskan populations). Microsatellites also substantiate the bidirectional patterns of gene flow previously uncovered using chloroplast DNA but indicate much greater movement and mixing. Results from our Bayesian analyses also suggest the existence of additional cryptic refugia. However, the locations have been obscured by high gene flow (RST averaging 0.057 ± 0.004). [ABSTRACT FROM PUBLISHER]

Meta-analyses reveal that fast-growing species have a greater growth response to elevated CO2 than slow-growing species. It is unknown whether this is a direct response or whether inter-specific differences in growth are simply correlated with other physiological or morphological differences among species that affect the growth response to CO2. Here we use intra-specific variation in Picea glauca to examine the mechanistic basis for this relationship. Relative growth rate (RGR) of 29 genotypes grown at ambient (370 µl l−1) or elevated (740 µl l−1) CO2 was measured. Physiological and morphological traits describing differences in allocation, canopy structure, stomatal function and photosynthesis were determined. Most variation in RGR (74%) was explained by traits associated with canopy structure. Although there was a strong correlation between RGR740 and RGR370, we found no evidence that genotypes that grew fast at ambient CO2 had a greater relative growth response to CO2. Given that the pattern found at the intra-specific level differed from that reported at the inter-specific level, our results suggest that RGR per se does not affect the growth response to CO2. Rather, the CO2 growth response is determined by traits that may or may not be correlated with RGR. [ABSTRACT FROM AUTHOR]

The megagametophyte of white spruce (Picea glauca) seeds undergoes programmed cell death following seed germination. This process is characterized by distinct morphological and biochemical features, such as DNA fragmentation and the induction of proteases. Biphasic production of hydrogen peroxide was detected in the megagametophyte following seed germination. ROS scavengers or inhibitors of ROS production decreased caspase-like protease activity and slowed the progression of cell death. One catalase (CAT) of white spruce reacted with antibodies directed against cotton-seed CAT. The corresponding CAT gene was cloned and compared with the catalase genes of other plant species. The activity of the white spruce CAT enzyme was stimulated by tyrosine phosphorylation. The phosphorylated CAT was subjected to ubiquitination and degraded by the proteasome. Furthermore, the proteasome inhibitor MG132 inhibited the degradation of CAT and delayed cell death. These results suggest that the interplay of CAT and the ubiquitin-mediated proteolytic system is critical in the control of ROS production and subsequent cell death. [ABSTRACT FROM PUBLISHER]

The biosynthesis of the tetracyclic diterpene ent-kaurene is a critical step in the general (primary) metabolism of gibberellin hormones. ent-Kaurene is formed by a two-step cyclization of geranylgeranyl diphosphate via the intermediate ent-copalyl diphosphate. In a lower land plant, the moss Physcomitrella patens, a single bifunctional diterpene synthase (diTPS) catalyzes both steps. In contrast, in angiosperms, the two consecutive cyclizations are catalyzed by two distinct monofurictional enzymes, ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS). The enzyme, or enzymes, responsible for ent- kaurene biosynthesis in gymnosperms has been elusive. However, several bifunctional diTPS of specialized (secondary) metabolism have previously been characterized in gymnosperms, and all known diTPSs for resin acid biosynthesis in conifers are bifurictional. To further understand the evolution of ent-kaurene biosynthesis as well as the evolution of general and specialized diterpenoid metabolisms in gymnosperms, we set out to determine whether conifers use a single bifunctional diTPS or two monofunctional diTPSs in the ent-kaurene pathway. Using a combination of expressed sequence tag, full-length cDNA, genomic DNA, and targeted bacterial artificial chromosome sequencing, we identified two candidate CPS and KS genes from white spruce (Picea glauca) and their orthologs in Sitka spruce (Picea sitchensis). Functional characterization of the recombinant enzymes established that ent-kaurene biosynthesis in white spruce is catalyzed by two monofunctional diTPSs, PgCPS and PgKS. Comparative analysis of gene structures and enzyme functions highlights the molecular evolution of these diTPSs as conserved between gymnosperms and angiosperms. In contrast, diTPSs for specialized metabolism have evolved differently in angiosperms and gymnosperms. [ABSTRACT FROM AUTHOR]

A variable-exponent stem profile model was developed for white spruce (Picea glauca (Moench) Voss) trees in Alberta using a nonlinear mixed model approach. Between-tree variation in stem diameter was best captured by incorporating three random parameters into the model. Heterogeneous residual variances were modelled as a power function of tree breast height diameter. Within-tree residual autocorrelation was modelled through a covariance structure. Based on model fitting statistics, the four-banded toeplitz (TOEP(4)) and the spatial power structures were both selected for further evaluation. An independent validation dataset was used for evaluating the calibration accuracy of the final model in stem diameter and volume predictions. To make tree-specific calibrations, one or more prior diameter measures should be available from each tree. For this study, four scenarios were evaluated, in which one, two, three and four prior diameters were randomly selected for predicting random parameters by an approximate Bayesian estimator. Tree-specific calibrations were subsequently derived. Population-level predictions were also produced for comparison. The TOEP(4) structure was better in general than the spatial power structure for predicting stem diameter and total tree and section volumes. [ABSTRACT FROM PUBLISHER]

This study examines the long-term effects of experimental conifer monocultures on stem volume and soil chemistry. Replicated plots of black spruce (Picea mariana), white spruce (Picea glauca), and red pine (Pinus resinosa) were planted in 1950 at three spacings (1.8, 2.7, and 3.6 m) on a briefly cultivated agricultural field on glaciolacustrine sandy loam soil near Thunder Bay, Ontario, Canada. Stem volumes per hectare and per tree were measured in 2002 (52 years after planting). Surface organic (i.e., forest floor) and mineral soil fertility in terms of pH, total N and P, and extractable NH4-N and P were measured in 2000 (50 years after planting). Of the three species red pine had the highest volume per hectare at all the three spacing followed by white spruce and black spruce; volume for all three species peaked at the 1.8-m spacing. The effects of conifer species on soil physical and chemical properties were more pronounced than spacing effects and the changes were mainly confined to forest floor layer. Few changes in mineral soil properties occurred because of the species and spacing treatments. Per hectare forest floor nutrient pools were higher under white spruce and red pine than black spruce, a pattern likely driven by higher litterfall and forest floor accumulation. It appears that toward the end of first rotation the higher productivity of red pine compared with the other conifers did not come at the cost of reduced soil pools of available NH4, P04, or K, but it was associated with reduced Ca levels in the forest floor. [ABSTRACT FROM AUTHOR]

Conifers are among the most genetically diverse plants but show the lowest levels of genetic differentiation, even among geographically distant populations. High gene flow among populations may be one of the most important factors in maintaining these genetic patterns. Here, we provide empirical evidence for extensive pollen-mediated gene dispersal between natural stands of a widespread northern temperate/boreal conifer, Picea glauca. We used 6 polymorphic allozyme loci to quantify the proportion of seeds sired by pollen originating from different sources in a landscape fragmented by agriculture in North Central Ontario, Canada. In 7 stands, a small proportion of seeds were sired by self-pollen or neighboring trees but 87.1% (±1.7% standard error [SE]) of seeds were sired by pollen from at least 250 to 3000 m away. In 4 single isolated trees, self-fertilization rates were low and more than 96% (±1.3% SE) of seeds were sired by immigrant pollen. The average minimum pollen dispersal distance in outcrossed matings was 619 m. These results provide strong evidence that extensive long-distance pollen dispersal plays a primary role in maintaining low genetic differentiation among natural populations of P. glauca and helps maintain genetic diversity and minimize inbreeding in small stands in a fragmented landscape. [ABSTRACT FROM AUTHOR]

Four full-sib families of interior spruce (Picea glauca (Moench) Voss) × Picea engelmanii Parry ex Engelm.) with contrasting growth rates (two fast-growing and two slow-growing families) were grown aeroponically with either a 2% relative nitrogen addition rate or free access to nitrogen. Fast-growing families showed greater plasticity in allocating biomass to shoots at high nitrogen supply and to roots at low nitrogen supply than slow-growing families. Compared with the slow-growing families, short-term net ammonium uptake rate measured with an ion selective electrode was significantly greater in fast-growing families at high ammonium supply, but not at low supply. Net nitrate uptake showed the same trend, but differences among families were not significant. Results indicate that differences in seedling growth rate are partly a result of physiological differences in net nitrogen uptake efficiency and nitrogen productivity. [ABSTRACT FROM PUBLISHER]

The interactions among white spruce, Picea glauca (Moench) Voss, purified acetone tannin extracts (hydrolyzable and condensed tannin), Bacillus thuringiensis subsp. kurstaki CrylA (c) δ-endotoxin strain HD-73 (Btk), and spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) on larval survival, growth, and development were investigated over the whole larval feeding period by using artificial diet supplemented with three concentrations of Btk toxins per milliliter of diet (0, 0.021, and 1.72 μg/ml) and three concentrations of foliar tannin extract (0, 8, and 15% dry mass basis). At high Btk concentration, tannin antagonized Btk potency against spruce budworm by lowering Btk-related larval mortality from 83 to 43%. At moderate Btk concentration tannin did not affect Btk potency. Host tree tannins antagonized not only the lethal effects of Btk toxin but also sublethal Btk-related impacts in terms of larval development, pupal weight, relative consumption rate, and growth rate. When alone in the diet, tannin negatively affected larval survival, growth, and development. Maximum potency of tannins against spruce budworm larvae (60% mortality) was reached at dietary concentrations corresponding to what is found in the plant (8% dry mass). The addition of Btk toxin in food containing tannin reduced percentage of larval mortality by one-third, indicating that Btk toxin can antagonize tannin potency against the insect. Development of Btk transgenic spruce trees should consider the antagonistic effect the toxin may have on the resistance conferred by tannins that have evolved naturally in spruce trees. [ABSTRACT FROM AUTHOR]

• Background and Aims Burial is a recurrent stress imposed upon plants of coastal dunes. Woody plants are buried on open coastal dunes and in forested areas behind active blowouts; however, little is known about the burial responses and adaptive traits of these species. The objectives of this study were: (a) to determine the growth and morphological responses to burial in sand of seven woody plant species native to central Canadian coastal dunes; and (b) to identify traits that determine burial tolerance in these species.• Methods Field experiments were conducted to determine the responses of each species to burial. Saplings were exposed to burial treatments of 0, 10, 25, 50 and 75 % of their height. Burial responses were evaluated based on regressions of total biomass, height, adventitious root production and percentage allocation to shoot, root and adventitious root biomass on percentage burial.• Key ResultsPinus strobus and Picea glauca lacked burial tolerance. In response to the burial gradient, these species showed a strong linear decline in total biomass, minimal adventitious root production that peaked at moderate levels (25–50 % burial) and no change in allocation to shoots vs. roots. The tolerant species Juniperus virginiana, Thuja occidentalis and Picea mariana showed a quadratic response to burial, with little change in biomass up to 50 % burial, but a large decline at 75 %. These species produced abundant adventitious roots up to 50 % burial, but did not alter allocation patterns over the range of burial levels. Populus balsamifera and Salix cordata were stimulated by burial. These species showed linear increases in biomass with increasing burial, produced copious adventitious roots across the gradient and showed a clear shift in allocation to vertical shoot growth and adventitious root production at the expense of the original roots under high burial conditions.• Conclusions Adventitious root production and plastic resource allocation to biomass are adaptive traits of coastal dune woody plants in central Canada, and provide a basis for assessing burial tolerance in woody plants on coastal dunes throughout the world. [ABSTRACT FROM AUTHOR]

Eastern dwarf mistletoe (Arceuthobium pusillum Peck) is a hemiparasitic angiosperm that infects white spruce (Picea glauca (Moench) Voss) and red spruce (P. rubens Sarg.) in northeastern North America. The effects of mistletoe infection differ substantially between white and red spruce, with white spruce suffering greater infection-induced mortality. In the present study, we sought to determine the role that species-specific differences in needle-scale responses to parasitism may play in the observed differences in the effect of infection on host tree health. Based on the measurements made, the most apparent effect of parasitism was a reduction in needle size distal to infections. The magnitude of this reduction was greater in white spruce than in red spruce. Eastern dwarf mistletoe was a sink for host photosynthate in red spruce and white spruce; however, there were no adjustments in needle photosynthetic capacities in either host to accommodate the added sink demands of the parasite. Needle total nonstructural carbohydrate concentrations (TNC) were also unaltered by infection. Red spruce needles had higher TNC concentrations despite having lower overall photosynthetic capacities, suggesting that red spruce may be more sink limited and therefore better able to satisfy the added sink demands of parasitic infection. However, if carbon availability limits the growth of the mistletoe, one may expect that the extent of the parasitic infection would be greater in red spruce. Yet in the field, the extent of infection is generally greater in white spruce. Taken together, these results suggest that dwarf mistletoe may not substantially perturb the carbon balance of either host spruce species and that species-specific differences in needle-scale responses to the parasite cannot explain the contrasting effects of infection on white spruce and red spruce. [ABSTRACT FROM AUTHOR]

A new member of the Argonaute (AGO) family of proteins was isolated from conifers and designated as PgAGO (Gene Bank Accession No. DQ068741; protein ID AAY67884). The complete coding sequence of PgAGO was obtained through screening cDNA libraries generated from white spruce (Picea glauca (Moench) Voss) somatic embryos. The PgAGO gene has an open reading frame of 2880 bp and encodes a protein of 960 amino acids. The predicted protein has an isolectric point of 9.17, a molecular mass of 107 kD and lacks prominent hydrophobic domains, which makes its cellular location inconclusive. The PgAGO protein contains the two conserved regions (the PAZ and PIWI domains) typically found in all members of the AGO family. The PAZ domain of PgAGO comprises 117 amino acid residues and shares a low degree of homology with similar domains in other species. The C-terminal PIWI domain contains 86 amino acids and is more conserved. Localization and transformation studies suggest that PgAGO is required for embryo development, specifically for proper shoot and root apical meristem differentiation. Based on RNA-in situ hybridization, the PgAGO transcripts are preferentially localized in cells of the shoot and root apical meristems from the early phases of embryo development. The RNA-mediated suppression of PgAGO results in severe abnormalities during embryo development, including the formation of poorly organized apical meristems. The root meristems lack the group of large central cells that separate the procambial region from the root cap, whereas the shoot meristem fails to differentiate apical initials. These abnormalities result in poor post-embryonic performance, leading to meristem abortion and growth cessation. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that, in some cell lines, exogenous applications of ascorbic acid (ASC) enhance the conversion frequency of white spruce (Picea glauca (Moench) Voss) somatic embryos, by stimulating mitotic activity in the apical meristems. To examine this event in more detail, we investigated the effects of ASC on de novo, salvage and degradation pathways of pyrimidine metabolism by following the metabolic fate of 14C-labeled orotic acid, thymidine, uridine and uracil in shoot and root poles of germinating embryos, after altering the cellular ASC content of the embryos. Alterations in endogenous ASC content did not affect the utilization of either orotic acid or uracil, but affected the metabolism of thymidine and uridine. Specifically, a lowering of endogenous ASC content by applications of lycorine (L), an inhibitor of the last enzyme of the ASC de novo biosynthetic pathway, resulted in a lower embryo conversion frequency, as well as a reduced percentage of thymidine and uridine incorporated into nucleotides and nucleic acids. The reduction in thymidine and uridine anabolism was mainly ascribed to the decreased activities of thymidine kinase (TRK) and uridine kinase (URK), the respective salvage enzymes of thymidine and uridine, measured in L-treated embryos. These effects were solely a result of a decrease in endogenous ASC content because applications of ascorbic acid plus lycorine (ASC + L) increased embryo conversion frequency, thymidine and uridine salvage activities, and TRK and URK activities to near control values. Inclusion of exogenous ASC in the germination medium did not affect the percentage of embryos able to convert to viable plantlets, although it increased thymidine and uridine utilization for nucleic acid synthesis in the shoot and root poles of the embryos. Taken together, these findings confirm that cellular ASC plays a key role in the reactivation of the apical meristems of germinating white spruce somatic embryos. [ABSTRACT FROM PUBLISHER]

We tested the effects of ectomycorrhizal (ECM) inoculation on greenhouse-grown white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana L.) seedlings to be used for revegetation of salt-affected tailing sands resulting from the exploitation of oil sand in northeastern Alberta, Canada. White spruce and jack pine seedlings were inoculated with three ECM fungi selected for their in vitro tolerance to excess Na+ and Cl−: Hebeloma crustuliniforme (Bull) Quel. UAMH 5247, Laccaria bicolor Maire (Orton) UAMH 8232 and a Suillus tomentosus (Kauff.) Sing., Snell and Dick isolate from a salt-affected site. The physiological responses of the seedlings to a gradient of NaCl concentration (0, 50, 100 and 200 mM) were assessed over four weeks by: (1) Na+ accumulation and allocation; (2) chlorophyll a fluorescence; (3) growth, (4) water content; and (5) organic osmolyte accumulation. Jack pine seedlings were more sensitive than white spruce seedlings to increasing Na+ and Cl− concentrations. Both species showed decreasing biomass accumulation, and increasing concentrations of organic osmotica and Na with increasing NaCl concentration. White spruce seedlings inoculated with the S. tomentosus isolate had the best growth response at all NaCl concentrations tested. Although jack pine seedlings inoculated with the L. bicolor or S. tomentosus isolate exhibited the highest growth in the 50 and 100 mM NaCl treatments, both fungi increased the photochemical stress and dehydration of their hosts in the 200 mM NaCl treatment. At the latter concentration, jack pine seedlings inoculated with H. crustuliniforme showed the greatest tolerance to salt stress. Although the different fungi altered the physiological response of the host in different ways, inoculation with salt-stress-tolerant ECM fungi increased growth and reduced the negative effects of excess NaCl. Use of controlled mycorrhization may increase survival of coniferous seedlings used for revegetation of salt-affected sites. [ABSTRACT FROM PUBLISHER]

Two temperature regimes were applied during reproductive development of seed and pollen cones of interior spruce (Picea glauca (Moench) Voss and Picea engelmannii (Parry) complex) to determine temperature effects on the adaptive traits of progeny. In Experiment 1, identical crosses were made on potted interior spruce using untreated pollen followed by exposure to a day/night temperature of 22/8 or 14/8 °C with a 12-h photoperiod during the stages of reproductive development from post-pollination to early embryo development. Frost hardiness and growth of progeny from seed produced in the two temperature treatments were measured over a 4-year period. Elevated temperature significantly affected both seed-cone development and the adaptive properties of the progeny. Seed cones exposed to the 22/8 °C treatment reached the early embryo stage in 53 days versus 92 days in the 14/8 °C treatment. Seed yields, cotyledon emergence and percent germination were also significantly enhanced by the 22/8 °C treatment. Progeny from seed produced in the higher temperature treatment showed significantly reduced spring and fall frost hardiness, but the elevated temperature treatment had no significant effects on time of bud burst, growth patterns or final heights. In Experiment 2, single ramets of the same clone were subjected to a day/night temperature of 20/8 or 10/8 °C during pollen cone development, starting from meiosis and ending at pollen shedding. The two populations of pollen were then crossed with untreated seed cones. Compared with pollen cones exposed to the 10/8 °C treatment, pollen cones exposed to the 20/8 °C treatment during development reached the shedding stage 2–4 weeks earlier, whereas pollen yields, in vitro viability and fertility (seed set) were significantly lower; however, the resulting progeny displayed no treatment differences in frost hardiness or growth after 1 year. Results suggest that seed orchard after-effects could be caused by temperature differences between orchard site and parent tree origin and that this effect acts on maternal development. Gametophytic (pollen or megagametophyte or both) and early embryo (sporophytic) selection are possible mechanisms that may explain the observed results. Although the effects are biologically significant, they are relatively small and do not justify changes in current deployment strategies for seed orchard seed. [ABSTRACT FROM AUTHOR]