Publications - Genetics, Tree Improvement, and Biodiversity

A remote sensing approach to biodiversity assessment and regionalization of the Canadian boreal forest.

Tue, 19 Mar 2013

Successful conservation planning for the Canadian boreal forest requires biodiversity data that are both accessible and reliable. Spatially exhaustive data is required to inform on conditions, trends, and context, with context enabling consideration of conservation opportunities and related trade-offs. However, conventional methods for measuring biodiversity, while useful, are spatially constrained, making it difficult to apply over wide geographic regions. Increasingly, remotely sensed imagery and methods are seen as a viable approach for acquiring explicit, repeatable and multi-scale biodiversity data over large areas. To identify relevant remotely derived environmental indicators specific to biodiversity within the Canadian boreal forest, we assessed indicators of the physical environment such as seasonal snow cover, topography, and vegetation production. Specifically, we determined if the indicators provided distinct information and whether they were useful predictors of species richness (tree, mammal, bird and butterfly species). Using cluster analysis, we also assessed the applicability of these indicators for broad ecosystem classification of the Canadian boreal forest and the subsequent attribution of these stratified regions (i.e., clusters). Our results reveal that the indicators used in the cluster creation provided unique information and explained much of the variance in tree (92.6 %), bird (84.6 %), butterfly (61.4 %) and mammal (22.6 %) species richness. Spring snow cover explained the most variance in species richness. Results further show that the fifteen clusters produced using cluster analysis were principally stratified along a latitudinal gradient and, while varied in size, captured a range of different environmental conditions across the Canadian boreal forest. The most important indicators for discriminating between the different cluster groups were seasonal greenness, a multipart measure of climate, topography and land use, and wetland cover, a measure of the percentage of wetland within a 1 km² cell.

Development of high-density SNP genotyping arrays for white spruce (Picea glauca) and transferability to subtropical and nordic congeners.

Mon, 25 Feb 2013

High-density SNP genotyping arrays can be designed for any species given sufficient sequence information of high quality. Two high-density SNP arrays relying on the Infinium iSelect technology (Illumina) were designed for use in the conifer white spruce (Picea glauca). One array contained 7338 segregating SNPs representative of 2814 genes of various molecular functional classes for main uses in genetic association and population genetics studies. The other one contained 9559 segregating SNPs representative of 9543 genes for main uses in population genetics, linkage mapping of the genome and genomic prediction. The SNPs assayed were discovered from various sources of gene resequencing data. SNPs predicted from high-quality sequences derived from genomic DNA reached a genotyping success rate of 64.7%. Nonsingleton in silico SNPs (i.e. a sequence polymorphism present in at least two reads) predicted from expressed sequenced tags obtained with the Roche 454 technology and Illumina GAII analyser resulted in a similar genotyping success rate of 71.6% when the deepest alignment was used and the most favourable SNP probe per gene was selected. A variable proportion of these SNPs was shared by other nordic and subtropical spruce species from North America and Europe. The number of shared SNPs was inversely proportional to phylogenetic divergence and standing genetic variation in the recipient species, but positively related to allele frequency in P. glauca natural populations. These validated SNP resources should open up new avenues for population genetics and comparative genetic mapping at a genomic scale in spruce species.

Evaluation of qPCR curve analysis methods for reliable biomarker discovery: Bias, resolution, precision, and implications.

Mon, 29 Apr 2013

RNA transcripts such as mRNA or microRNA are frequently used as biomarkers to determine disease state or response to therapy. Reverse transcription (RT) in combination with quantitative PCR (qPCR) has become the method of choice to quantify small amounts of such RNA molecules. In parallel with the democratization of RT-qPCR and its increasing use in biomedical research or biomarker discovery, we witnessed a growth in the number of gene expression data analysis methods. Most of these methods are based on the principle that the position of the amplification curve with respect to the cycle-axis is a measure for the initial target quantity: the later the curve, the lower the target quantity. However, most methods differ in the mathematical algorithms used to determine this position, as well as in the way the efficiency of the PCR reaction (the fold increase of product per cycle) is determined and applied in the calculations. Moreover, there is dispute about whether the PCR efficiency is constant or continuously decreasing. Together this has lead to the development of different methods to analyze amplification curves. In published comparisons of these methods, available algorithms were typically applied in a restricted or outdated way, which does not do them justice. Therefore, we aimed at development of a framework for robust and unbiased assessment of curve analysis performance whereby various publicly available curve analysis methods were thoroughly compared using a previously published large clinical data set (Vermeulen et al., 2009). The original developers of these methods applied their algorithms and are co-author on this study. We assessed the curve analysis methods' impact on transcriptional biomarker identification in terms of expression level, statistical significance, and patient-classification accuracy. The concentration series per gene, together with data sets from unpublished technical performance experiments, were analyzed in order to assess the algorithms’ precision, bias, and resolution. While large differences exist between methods when considering the technical performance experiments, most methods perform relatively well on the biomarker data. The data and the analysis results per method are made available to serve as benchmark for further development and evaluation of qPCR curve analysis methods (http://qPCRDataMethods.hfrc.nl).

Fast-growing tree plantations: a source of bioenergy. Branching out from the Canadian Forest Service, Laurentian Forestry Centre. No. 79.

Wed, 27 Mar 2013

Growth: a key issue.

Abitibi-Témiscamingue: an experimental land.

Greenhouse or field testing: a matter of time.

A growing phenomenon.

Organic nitrogen composition of the tissue culture medium influences Agrobacterium tumefaciens growth and the recovery of transformed Pinus radiata embryonal masses after cocultivation.

Mon, 25 Feb 2013

Repeated attempts to genetically transform Pinus radiata embryonal masses through cocultivation with Agrobacterium tumefaciens on MSG medium were unproductive due to Agrobacterium overgrowth. Timentin at either 200 or 400 mgl^-1 was ineffective in inhibiting bacterial growth after cocultivation. In this study, the causes of the abundant bacterial growth were investigated by comparing MSG medium with two other media (mLVand DCR) commonly used in conifer somatic embryogenesis. Statistical analysis of the growth data (optical density and number of cell-forming units) showed that bacterium grew significantly more on MSG than on mLV or DCR during the 48-h cocultivation. This enhanced growth was attributed to the higher concentration of L-glutamine in MSG. Lowering the concentration of L-glutamine in MSG to 0.5 gl^-1 resulted in similar growth of Agrobacterium compared with the other two media. MSG was also superior for the growth of radiata pine cells, with a statistically significant difference after 14 d of culture. Hence, to avoid bacterial overgrowth during and after cocultivation, a two-medium protocol was developed in which cocultivation was carried out on mLV, followed by 5 d on mLV with 400 mgl^-1 Timentin. Selection for transformed cells and further control of bacterial growth was then performed using MSG with Timentin and Geneticin. By sequential application of these two media, 2,096 cell colonies were selected; of these, 94 were analyzed and 49 were transgenic. These results highlight yet another factor that might be critical for the success of transformation experiments but has not been sufficiently studied until now: the growth dynamics and ability to eliminate A. tumefaciens on various plant tissue culture media.

Origins and diversity of the introduced southern red-backed vole (Myodes gapperi) population in Newfoundland, Canada based on mitochondrial haplotypes: ecological and management implications of a potentially invasive species.

Thu, 07 Mar 2013

Inferences about sources and routes of colonization are important to understanding and managing introduced species. The southern red-backed vole (SRBV: Myodes gapperi), not native to Newfoundland, was recently discovered in the western interior of the island, and its range is rapidly expanding. Theories regarding the origin of these animals include migration from an earlier release on a small coastal island, accompaniement of pulpwood imports, or an unsanctioned release as part of Newfoundland marten (Martes americana atrata) recovery efforts. To determine the source, route, and potential timing of introduction to the island, we analyzed mitochondrial control-region sequences of 155 animals from Newfoundland and the two most likely sources, Cape Breton and Labrador. Although Cape Breton and Labrador contain phylogenetically distinct suites of haplotypes, both regions are part of the "eastern" clade of SRBV, indicating that the northeastern-most part of the range was recolonized from an eastern forest refugial lineage isolated during the Pleistocene. The Newfoundland population of SRBV contained only two haplotypes, one found in 89 individuals from multiple sampling locations that clusters with the Cape Breton subclade, and the other found in three individuals from Mine Pond and five from Labrador. We conclude that there have been at least two introductions to the island, with the Cape Breton-sourced introduction occurring earlier than the Labrador event; low diversity is consistent with recent timing of these events. Success of introduced voles in Newfoundland, despite little genetic diversity, probably reflects an exploitable niche for a broadly adapted boreal small mammal.

Patterns of cross-continental variation in tree seed mass in the Canadian boreal forest

Thu, 18 Apr 2013

Seed mass is an adaptive trait affecting species distribution, population dynamics and community structure. In widely distributed species, variation in seed mass may reflect both genetic adaptation to local environments and adaptive phenotypic plasticity. Acknowledging the difficulty in separating these two aspects, we examined the causal relationships determining seed mass variation to better understand adaptability and/or plasticity of selected tree species to spatial/ climatic variation. A total of 504, 481 and 454 seed collections of black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb) across the Canadian Boreal Forest, respectively, were selected. Correlation analyses were used to determine how seed mass vary with latitude, longitude, and altitude. Structural Equation Modeling was used to examine how geographic and climatic variables influence seed mass. Climatic factors explained a large portion of the variation in seed mass (34, 14 and 29%, for black spruce, white spruce and jack pine, respectively), indicating species-specific adaptation to long term climate conditions. Higher annual mean temperature and winter precipitation caused greater seed mass in black spruce, but annual precipitation was the controlling factor for white spruce. The combination of factors such as growing season temperature and evapotranspiration, temperature seasonality and annual precipitation together determined seed mass of jack pine. Overall, sites with higher winter temperatures were correlated with larger seeds. Thus, long-term climatic conditions, at least in part, determined spatial variation in seed mass. Black spruce and Jack pine, species with relatively more specific habitat requirements and less plasticity, had more variation in seed mass explained by climate than did the more plastic species white spruce. As traits such as seed mass are related to seedling growth and survival, they potentially influence forest species composition in a changing climate and should be included in future modeling of vegetation shifts.

Plantations d’espèces à croissance rapide : une source de bioénergie. L’éclaircie du Service canadien des forêts, Centre de foresterie des Laurentides. No 79.

Wed, 27 Mar 2013

Growth: a key issue.

Abitibi-Témiscamingue: an experimental land.

Greenhouse or field testing: a matter of time.

A growing phenomenon.

Tree size affects accumulation of carbon and nitrogen metabolites in white spruce seedlings during short day-induced bud formation.

Fri, 11 Jan 2013

The present study documents the changes in carbon and nitrogen metabolites occurring in apical buds and previous year stems of white spruce seedlings (Picea glauca [Moench] Voss) with contrasting growth phenotypes (tall vs. small) after transfer to short day (SD; 8 h) photoperiod to induce bud formation. Concentrations of total nonstructural carbohydrates markedly increased in the developing buds within the days after transfer to SD, mainly as a result of increased concentrations of monosaccharides such as glucose, fructose, and pinitol. At the same time, starch levels declined, with the resulting carbohydrates presumably used to meet early carbon requirements of the SD-induced apical bud. Concentrations of glutamine, glutamic acid and proline also decreased immediately after transfer to SD in both organs. Later stages of SDinduced bud formation were characterized by an increase in starch, sucrose, and glutamine concentrations in previous year stems, concomitant with an increase in the steady-state levels of UDP-glucose pyrophosphorylase and glutamine synthetase protein. In contrast, arginine levels increased after 2 weeks of SD exposure, indicating a transition in arginine metabolism at the time of initiation of shoot stem primordia and bud elongation. Higher accumulation of total nonstructural carbohydrates and total amino acids in previous year stems of small trees could indicate lower sink strength of apical bud during its development, which could in turn impact subsequent tree growth.

Integrating vegetative propagation, biotechnologies and genetic improvement for tree production and sustainable forest management

Fri, 12 Apr 2013

A cysteine-rich antimicrobial peptide from Pinus monticola (PmAMP1) confers resistance to multiple fungal pathogens in canola (Brassica napus)

Wed, 30 May 2012

Canola (Brassica napus), an agriculturally important oilseed crop, can be significantly affected by diseases such as sclerotinia stem rot, blackleg, and alternaria black spot resulting in significant loss of crop productivity and quality. Cysteine-rich antimicrobial peptides isolated from plants have emerged as a potential resource for protection of plants against phytopathogens. Here we report the significance of an antimicrobial peptide, PmAMP1, isolated from western white pine (Pinus monticola), in providing canola with resistance against multiple phytopathogenic fungi. The cDNA encoding PmAMP1 was successfully incorporated into the genome of B. napus, and it’s in planta expression conferred greater protection against Alternaria brassicae, Leptosphaeria maculans and Sclerotinia sclerotiorum. In vitro experiments with proteins extracted from transgenic canola expressing Pm-AMP1 demonstrated its inhibitory activity by reducing growth of fungal hyphae. In addition, the in vitro synthesized peptide also inhibited the growth of the fungi. These results demonstrate that generating transgenic crops expressing PmAMP1 may be an effective and versatile method to protect susceptible crops against multiple phytopathogens.

A spruce gene map infers ancient plant genome reshuffling and subsequent slow evolution in the gymnosperm lineage leading to extant conifers.

Wed, 12 Dec 2012

Background: Seed plants are composed of angiosperms and gymnosperms, which diverged from each other around 300 million years ago. While much light has been shed on the mechanisms and rate of genome evolution in flowering plants, such knowledge remains conspicuously meagre for the gymnosperms. Conifers are key representatives of gymnosperms and the sheer size of their genomes represents a significant challenge for characterization, sequencing and assembling.

Results: To gain insight into the macro-organisation and long-term evolution of the conifer genome, we developed a genetic map involving 1,801 spruce genes. We designed a statistical approach based on kernel density estimation to analyse gene density and identified seven gene-rich isochors. Groups of co-localizing genes were also found that were transcriptionally co-regulated, indicative of functional clusters. Phylogenetic analyses of 157 gene families for which at least two duplicates were mapped on the spruce genome indicated that ancient gene duplicates shared by angiosperms and gymnosperms outnumbered conifer-specific duplicates by a ratio of eight to one. Ancient duplicates were much more translocated within and among spruce chromosomes than conifer-specific duplicates, which were mostly organised in tandem arrays. Both high synteny and collinearity were also observed between the genomes of spruce and pine, two conifers that diverged more than 100 million years ago.

Conclusions: Taken together, these results indicate that much genomic evolution has occurred in the seed plant lineage before the split between gymnosperms and angiosperms, and that the pace of evolution of the genome macro-structure has been much slower in the gymnosperm lineage leading to extent conifers than that seen for the same period of time in flowering plants. This trend is largely congruent with the contrasted rates of diversification and morphological evolution observed between these two groups of seed plants.

A test of ecological succession hypotheses using 55-year time-series data for 361 boreal forest stands

Thu, 18 Apr 2013

There has been much work on succession over many decades, but succession fundamentals are still debated because of the reliance on chronosequences and dendrochronological reconstruction, both of which are problematic approaches. Here we use time-series data to test four hypotheses that lie at the heart of successional theory: (1) the neighbourhood effect hypothesis – tree species abundance is time dependent; (2) the density-dependence hypothesis – a rare species is more favoured over time; (3) the resource ratio hypothesis – species that can grow at the lowest resource level tend to dominate resource limited sites through succession; and (4) the intermediate disturbance hypothesis – intermediate disturbances increase the abundance of rare species.

Advances in spruce genomics, quantitative genetics and population genetics at the Canadian Forest Service, Canadian Wood Fibre Centre, Quebec Region.

Fri, 18 Jan 2013

Anti-microbial peptide (AMP): nucleotide variation, gene expression, and host resistance in the white pine blister rust (WPBR) pathosystem

Tue, 18 Sep 2012

Pinus monticola antimicrobial peptide (PmAMP1) inhibits growth of Cronartium ribicola and other fungal pathogens. C. ribicola causes white pine blister rust and has resulted in a dramatic reduction of native white pines across North America. Quantitative disease resistance (QDR) is a highly desirable trait screened in breeding programs for durable resistance against C. ribicola. Along with phenotyping on a collection of germplasms, we analyzed PmAMP1 transcript and protein expression and re-sequenced the full-length gene including its promoter region. A mixed linear model was used to identify the association of single nucleotide polymorphisms (SNPs) with accumulated protein and stem QDR levels. Among 16 PmAMP1 SNPs identified in the present study, we found an association of protein levels with 6 SNPs (P < 0.05), including 2 in the 5′-untranslated region (UTR), 3 in the open reading frame (ORF) region with 2 nonsynonymous SNPs, and 1 SNP in the 3′-UTR. Another set of six SNPs was associated with stem QDR levels (P < 0.05), with one localized in the promoter region and the other five in the ORF region with four nonsynonymous changes, suggesting that multiple isoforms may have antifungal activity to differing degrees. Of three common PmAMP1 haplotypes, the trees with haplotype 2 showed high QDR levels with moderate protein abundance while those trees with haplotype 3 exhibited low QDR levels in the susceptible range and the lowest level of protein accumulation. Thus, an association of gene variations with protein abundance and resistance-related traits may facilitate elucidation of physiological contribution of PmAMP1 to host resistance.

Comparative proteomic profiles of Pinus monticola needles during early compatible and incompatible interactions with Cronartium ribicola

Tue, 18 Sep 2012

The proteomic profiles of primary needles from Cr2-resistant and cr2-susceptible Pinus monticola seedlings were analysed post Cronartium ribicola inoculation by 2-DE. One hundred-and-five protein spots exhibiting significant differential expression were identified using LC–MS/MS. Functional classification showed that the most numerous proteins are involved in defence signalling, oxidative burst, metabolic pathways, and other physiological processes. Our results revealed that differential expression of proteins in response to C. ribicola inoculation was genotype- and infection-stage dependent. Responsive proteins in resistant seedlings with incompatible white pine blister rust (WPBR) interaction included such well-characterized proteins as heat shock proteins (HSPs), reactive oxygen species (ROS) scavenging enzymes, and intermediate factors functioning in the signal transduction pathways triggered by well-known plant R genes, as well as new candidates in plant defence like sugar epimerase, GTP-binding proteins, and chloroplastic ribonucleoproteins. Fewer proteins were regulated in susceptible seedlings; most of them were in common with resistant seedlings and related to photosynthesis among others. Quantitative RT-PCR analysis confirmed HSP- and ROS-related genes played an important role in host defence in response to C. ribicola infection. To the best of our knowledge, this is the first comparative proteomics study on WPBR interactions at the early stages of host defence, which provides a reference proteomic profile for other five-needle pines as well as resistance candidates for further understanding of host resistance in the WPBR pathosystem.

Ectopic expression of a truncated Pinus radiata AGAMOUS homolog (PrAG1) causes alteration of inflorescence architecture and male sterility in Nicotiana tabacum

Wed, 30 May 2012

Plant MADS-box genes of the AG/PLE subfamily control the identity of sexual organs. An AG-homologous gene (PrAG1) was characterized in the Pinus radiata genome. PrAG1 transcript was detected only in the female and male strobili. To investigate its regulatory function during floral development, three binary vectors were constructed and transformed into tobacco plants for overexpression of the PrAG1 full-length protein (35S::MIKC), and truncated proteins with deletion of C domain (35S::MIK) or deletion of both C and K domains (35S::MI) under control of the CaMV 35S promoter. All transgenic tobacco lines with ectopic expression of 35S::MIKC and 35S::MIK showed no phenotypic effect on floral development. However, 23.8% of the 35S::MI transgenic lines displayed altered inflorescence architecture and variety of floral development changes, including complete male sterility, suggesting that PrAG1 may be the P. radiata AG-homologous gene with C-function and that it may play a role in the determination of meristem identities in both inflorescence and flowering. Expression of truncated AG MI genes could be useful in reducing plant pollen and seed formation, as well as increasing inflorescence branching and flower production, providing a novel engineered sterility strategy for transgenic plants with potential commercial application in molecular breeding of horticultural flowering plants.

Fine and coarse root parameters from mature black spruce displaying genetic X soil moisture interaction in growth

Tue, 18 Dec 2012

Fine and coarse root biomass, C, and N mass parameters were assessed by root size and soil depths from soil cores in plots of 32-year-old black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) from four full-sib families studied previously for drought tolerance and differential productivity on a dry and wet site. All fine and coarse root size categories had greater root biomass on the dry than on the wet site. Most of the site differences resided in 0-20 cm soild depth. The wet site had greater root N concentration than the dry site, despite the same soil N; thus, virtually no differences were observed in total fine and coarse root N mass between sites. Root N concentration declined with increases in both soil depth and root size. Fine roots (<2 mm) accounted for 73% and 38% of the total fine and coarse N mass, respectively. The dry site had lower needle mass and more fine root mass than the wet site, demonstrating an adaptation to moisture stress change through the rebalancing of resource-obtaining organs. Drought-tolerant families had the same quantity of fine roots as drought-intolerant families but were able to support more foliage and aboveground mass per unit fine root mass than intolerant families.

Forest biodiversity: balancing economic opportunity with ecological sustainability. 2012. Frontline Policy Perspectives Note 6.

Tue, 11 Sep 2012

Genetic effects on wood quality traits of plantation-grown white spruce (Picea glauca) and their relationships with growth

Thu, 28 Jun 2012

Clonal repeatabilities on individual tree (H²_i) and clonal mean (H²_C) bases for growth (14-year height and volume), wood quality traits (latewood proportion, wood density, fiber length, and microfibril angle), and genotypic correlations among the traits were estimated, using 30 white spruce (Picea glauca [Moench] Voss) clones from six full-sib families (five per family). These families were selected from a clonally replicated test to represent different early growth categories: fast, moderate, and slow. Wood increment cores of the 30 clones were collected from two contrasting sites at age 19 years. For growth traits, in contrast to most wood quality traits, more genetic variation was accounted for by clone within family than by family within growth category. Both growth and wood quality traits appear to be under moderate genetic control, with H²_i = 0.20 - 0.36 and H²_C = 0.70 - 0.83. The only exception was microfibril angle (H²_C = 0.10 and H²_C = 0.34). Generally, faster growth resulted in a significantly lower latewood proportion and lower overall wood density. Selection for faster growth does not appear to impact on either fiber length or microfibril angle. Among the wood quality traits, significant genotypic association was observed only between latewood proportion and wood density. Despite the generally negative association between growth and wood density among families, several fast-growing clones maintained above-average density. This implies that, by adopting multiclonal forestry, one can simultaneously improve growth and wood density.

Genetic parameters and clonal variation in growth and nutritional traits of containerized white spruce somatic seedlings / Paramètres génétiques et variation clonale dans la croissance et les traits nutritionnels des boutures d’épinette blanche.

Mon, 03 Dec 2012

Clonal forestry can significantly increase forest productivity and its establishment requires a high level of clonal variation to maximize genetic gain and diversity. An evaluation of the genetic parameters of clones at a juvenile stage is necessary to better understand the amplitude of clonal variability and the degree of genetic control. The analysis of variance of white spruce clones showed a highly significant clonal effect for the majority of the growth characters at the end of both growing seasons and for the mineral status at the 2+0 stage. Our results reveal that height exhibits a high clonal heritability value which remained stable over the two growing seasons (H² _c= 0.60). Strong genotypic and phenotypic correlations were observed between height and diameter at the end of the first growing season and between height and the rest of the growth characters at the end of the second growing season. The strong clonal variation, genetic control and genetic correlation particularly of height found in this study indicate that the selection ability of the best performing clones is possible for intensive forest management.

Genetic parameters and performance stability of white spruce somatic seedlings in clonal tests.

Mon, 13 Feb 2012

The commercial use of white spruce varieties produced by somatic embryogenesis (SE) permits increased forest productivity compared to other reproductive technologies. However, the use of SE in clonal forestry requires an accurate assessment of genetic parameters and the performance stability of clones in plantations. For these reasons, two clonal tests were established of 52 white spruce somatic clones. In each clonal tests, we measured survival, bud dormancy, stem form, growth and branching characteristics of clones 4 years after outplanting. There was a large variability among clones for characteristics related to growth and branching. At this juvenile stage, the clonal heritability estimates for all characteristics remained low. Of all the characteristics studied, height had the highest heritability. The selection of the top 20 clones (38% of the clones) provided a genotypic gain in height of about 4% for the two planting sites, which is reasonable for such a low selection intensity. High genotypic correlations were observed between growth and branching characteristics. Although a significant site effect was observed for most characteristics, the genotype x site (G x E) interaction was low and consequently the correlation between the two sites for the same characteristic was high. The performance stability of the somatic clones at both sites indicates that opportunities exist for selection of clones that adapt and perform well over different ecological regions, permitting a tangible increase in forest productivity.

Genetic parameters of morphological and physiological characteristics of containerized white spruce (Picea glauca (Moench.) Voss) seedlings.

Mon, 13 Feb 2012

The root systems of containerized seedlings must be sufficiently developed and have adequate root plug cohesion to permit handling and the planting of the seedlings with minimal root damage. Genetic variability in morphological and physiological seedling characteristics of 75 open-pollinated white spruce families was estimated to determine whether genetic selection for improved seedling root systems is possible. Seedlings were grown for 2 years under standard cultural practices in a forest nursery. Gas exchange measurements and seedling morphological characteristics (height, diameter, shoot and root dry mass, root to shoot ratio) were measured at the end of the two growing seasons whereas seedling mineral (N, P, and K) status was assessed at the end of the first growing season. Genetic parameters (heritabilities—h²—and genetic correlations) were estimated for every seedling characteristic and a strong genetic control associated with a large genetic variation was observed at both family (0.20≤h²_f≤0.88) and individual (0.21≤²_i≤0.97) levels. A single, late-season measurement of physiological characteristics did not reveal physiological basis for family variability in seedling root growth. Nevertheless, the family variation was large enough to permit genetic improvement of 2-year-old seedling juvenile morphological characteristics. Strong, positive genetic correlations enable us to foresee using root collar diameter as an effective method for indirectly selecting white spruce families with heavier root systems.

Histopathology of the endophytic system and aerial shoots of Arceuthobium americanum infected by Colletotrichum gloeosporioides

Fri, 25 Nov 2011

Infection of the endophytic system of Arceuthobium americanum parasitizing Pinus contorta var. latifolia by the fungus Colletotrichum gloeosporioides was assessed on naturally infected and inoculated localized dwarf mistletoe plants. Two different techniques were utilized to attempt to inoculate C. gloeosporioides into the endophytic system: the fungus was applied as Stabileze formulated product onto cut A. americanum shoots and as a mycelial plug to wounded A. americanum infected host branches. The fungus was cultured from infected shoots and the basal cup region of naturally infected A. americanum, but not pine tissues that included the endophytic system. Following inoculation of cut shoots, the shoots were abscised from the dwarf mistletoe plant, and the fungus was not isolated 1 year after inoculation. The fungus was recovered from the wounded region of infections that were inoculated with a mycelial plug, but not outside of the wounded area. Hyphae with morphology that matched that of C. gloeosporioide were observed microscopically in the shoots and basal cup region of naturally infected A. americanum, but not in the samples from the inoculated treatments. Thus, we were unable to confirm that C. gloeosporioides infected the endophytic system of A. americanum parasitizing P. contorta var. latifolia, although xylem continuity between the aerial and endophytic systems was observed.

Improving the quality of white birch (Betula papyrifera) seed. II.

Fri, 08 Mar 2013