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  • 1.
    Funda, Tomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Department of Forest Genetics and Plant Physiology, UPSCSwedish University of Agricultural Sciences, Umeå, Sweden.
    Wennström, Ulfstand
    Almqvist, Curt
    Andersson Gull, Bengt
    Wang, Xiao-Ru
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Mating dynamics of Scots pine in isolation tents2016Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 12, nr 6, artikkel-id 112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seed orchards are forest tree production populations for supplying the forest industry with consistent and abundant seed crops of superior genetic quality. However, genetic quality can be severely affected by non-random mating among parents and the occurrence of background pollination. This study analyzed mating structure and background pollination in six large isolation tents established in a clonal Scots pine seed orchard in northern Sweden. The isolation tents were intended to form a physical barrier against background pollen and induce earlier flowering relative to the surrounding trees. We scored flowering phenology inside and outside the tents and tracked airborne pollen density inside and outside the seed orchard in three consecutive pollination seasons. We genotyped 5683 offspring collected from the tents and open controls using nine microsatellite loci, and assigned paternity using simple exclusion method. We found that tent trees shed pollen and exhibited maximum female receptivity approximately 1 week earlier than trees in open control. The majority of matings in tents (78.3 %) occurred at distances within two trees apart (about 5 m). Self-fertilization was relatively high (average 21.8 %) in tents without supplemental pollination (SP), but it was substantially reduced in tents with SP (average 7.7 %). Pollen contamination was low in open controls (4.8-7.1 %), and all tents remained entirely free of foreign pollen. Our study demonstrates that tent isolation is effective in blocking pollen immigration and in manipulating flowering phenology. When complimented with supplemental pollination, it could become a useful seed orchard management practice to optimize the gain and diversity of seed orchard crops.

  • 2.
    Hall, David
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå Plant Science Centre, Department of Forest Genetics and Plant PhysiologySwedish University of Agricultural Sciences, Umeå, Sweden.
    Hallingbäck, Henrik R.
    Wu, Harry X.
    Estimation of number and size of QTL effects in forest tree traits2016Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 12, nr 6, artikkel-id 110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mapping the genetic architecture of forest tree traits is important in order to understand the evolutionary forces that have shaped these traits and to facilitate the development of genomic-based breeding strategies. We examined the number, size, and distribution of allelic effects influencing eight types of traits using 30 published mapping studies (linkage and association mapping) in forest trees. The sizes of allelic effects, measured as the phenotypic variance explained, generally showed a severely right-skewed distribution. We estimated the numbers of underlying causal effects (n(qtl)) for different trait categories by improving a method previously developed by Otto and Jones (Genetics 156: 2093-2107, 2000). Estimates of n(qtl) based on association mapping studies were generally higher (median at 643) than those based on linkage mapping (median at 33). Comparisons with simulated linkage and association mapping data suggested that the lower n(qtl) estimates for the linkage mapping studies could partly be explained by fewer causal loci segregating within the full-sib family populations normally used, but also by the cosegregation of causal loci due to limited recombination. Disease resistance estimates based on linkage mapping studies had the lowest median of four underlying effects, while growth traits based on association mapping had about 580 effects. Theoretically, the capture of 50% of the genetic variation would thus require a population size of about 200 for disease resistance in linkage mapping, while growth traits in association mapping would require about 25,000. The adequacy and reliability of the improved method was successfully verified by applying it to the simulated data.

  • 3. Hamilton, Jill A.
    et al.
    De la Torre, Amanda R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Univ British Columbia, Dept Forest & Conservat Sci, Ctr Forest Conservat Genet, Vancouver, BC V6T 1Z4, Canada.
    Aitken, Sally N.
    Fine-scale environmental variation contributes to introgression in a three-species spruce hybrid complex2015Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 11, nr 1, artikkel-id 817Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybridization is common for many forest trees, where weak barriers to reproduction obscure species boundaries. We characterized the genomic structure of Picea populations comprising three species spanning two well-known contact zones, the Picea sitchensisxPicea glauca and the P. engelmanniixP. glauca hybrid zones, using a set of 71 candidate-gene single nucleotide polymorphisms. The genetic structure of populations suggests a complex genomic architecture shaped by interspecific gene flow and strong environmental selection, with increased genetic diversity in hybrids. The presence of admixture among all three species suggests that three-way hybrids with mixed ancestry occur where species ranges overlap in transitional environments. Significant clinal variation and associations with climatic variables (including continentality, temperature, and precipitation) differ between hybrid zones, indicating that individual species and their hybrids are adapted to distinct environmental niches. Allele-environmental association analysis revealed that most of the candidate genes with evidence of selection were unique to either the Sitkaxwhite or the Engelmannxwhite hybrid zones, with few shared between these zones. Management of these widespread and diverse gene pools will be best served through development of climate-based seed transfer, with recommended seed sources informed by a combination of genetic and climatic information for future climates.

  • 4. Isabel, Nathalie
    et al.
    Lamothe, Manuel
    Thompson, Stacey Lee
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, Québec, Canada.
    A second-generation diagnostic single nucleotide polymorphism (SNP)-based assay, optimized to distinguish among eight poplar (Populus L.) species and their early hybrids2013Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 9, nr 2, s. 621-626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapid identification of Populus L. species and hybrids can be achieved with relatively little effort through the use of primer extension-based single nucleotide polymorphism (SNP) genotyping assays. We present an optimized set of 36 SNP markers from 28 gene regions that diagnose eight poplar species (Populus angustifolia James, Populus balsamifera L., Populus deltoides Bartram, Populus fremontii Watson, Populus laurifolia Ledeb., Populus maximowiczii Henry, Populus nigra L., and Populus trichocarpa Torr. & Gray). A total of 700 DNA sequences from six Populus species (1–15 individuals per species) were used to construct the array. A set of flanking and probe oligonucleotides was developed and tested. The accuracy of the SNP assay was validated by genotyping 448 putatively "pure" individuals from 14 species of Populus. Overall, the SNP assay had a high success rate (97.6 %) and will prove useful for the identification of all Aigeiros Duby and Tacamahaca Spach. species and their early-generation hybrids within natural populations and breeding programs. Null alleles and intraspecific polymorphisms were detected for a few locus/species combinations in the Aigeiros and Tacamahaca sections. When we attempted to genotype aspens of the section Populus (Populus alba L., Populus grandidentata Michx., Populus tremula L., and Populus tremuloides Michx.), the success rate of the SNP array decreased by 13 %, demonstrating moderate cross-sectional transferability.

  • 5. Tuskan, Gerald A.
    et al.
    DiFazio, Steve
    Faivre-Rampant, Patricia
    Gaudet, Muriel
    Harfouche, Antoine
    Jorge, Veronique
    Labbe, Jessy L.
    Ranjan, Priya
    Sabatti, Maurizio
    Slavov, Gancho
    Street, Nathaniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Tschaplinski, Timothy J.
    Yin, Tongming
    The obscure events contributing to the evolution of an incipient sex chromosome in Populus: a retrospective working hypothesis2012Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 8, nr 3, s. 559-571Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Genetic determination of gender is a fundamental developmental and evolutionary process in plants. Although it appears that dioecy in Populus is genetically controlled, the precise gender-determining systems remain unclear. The recently released second draft assembly and annotated gene set of the Populus genome provided an opportunity to revisit this topic. We hypothesized that over evolutionary time, selective pressure has reformed the genome structure and gene composition in the peritelomeric region of the chromosome XIX, which has resulted in a distinctive genome structure and cluster of genes contributing to gender determination in Populus trichocarpa. Multiple lines of evidence support this working hypothesis. First, the peritelomeric region of the chromosome XIX contains significantly fewer single nucleotide polymorphisms than the rest of Populus genome and has a distinct evolutionary history. Second, the peritelomeric end of chromosome XIX contains the largest cluster of the nucleotide-binding site-leucine-rich repeat (NBS-LRR) class of disease resistance genes in the entire Populus genome. Third, there is a high occurrence of small microRNAs on chromosome XIX, which is coincident to the region containing the putative gender-determining locus and the major cluster of NBS-LRR genes. Further, by analyzing the metabolomic profiles of floral bud in male and female Populus trees using a gas chromatography-mass spectrometry, we found that there are gender-specific accumulations of phenolic glycosides. Taken together, these findings led to the hypothesis that resistance to and regulation of a floral pathogen and gender determination coevolved, and that these events triggered the emergence of a nascent sex chromosome. Further studies of chromosome XIX will provide new insights into the genetic control of gender determination in Populus.

  • 6. Viswanath, Venkatesh
    et al.
    Albrectsen, Benedicte R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Strauss, Steven H.
    Global regulatory burden for field testing of genetically modified trees2012Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 8, nr 2, s. 221-226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Field trials are widely known to be essential for understanding the value and adaptability of trees produced via conventional and transgenic biotechnologies. However, obtaining permission for transgenic field trials is often considered to be very difficult in many countries. To understand the extent of regulatory requirements around the world and the burdens they impose, we surveyed 36 scientists and practitioners from 20 different countries who had experience or direct knowledge of regulatory compliance with field trials of transgenic trees. Results showed that permits and monitoring were universally required, and that public disclosure of field trial locations was required in three quarters of countries. Other major findings were that: separate approvals for different constructs, tree species, and trial locations were required in more than three quarters of the countries; characterization of each transgene insertion event was required as part of the application in four fifths of countries; and the application process itself was perceived as the largest single burden. Regulatory tiers that differentiate different kinds of transgenic trees based on perceived risk were present in only one fifth of countries. The data confirm the widespread perception among scientists that the costs and burdens of conducting field trials with transgenic trees are nearly universal substantial impediments to scientific and breeding progress.

  • 7. Zas, Rafael
    et al.
    Björklund, Niklas
    Sampedro, Luis
    Hellqvist, Claes
    Karlsson, Bo
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Nordlander, Göran
    Genetic variation in resistance of Norway spruce seedlings to damage by the pine weevil Hylobius abietis2017Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 13, nr 5, artikkel-id 111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Regeneration of northern conifer forests is commonly performed by reforestation with genetically improved materials obtained from long-term breeding programs focused on productivity and timber quality. Sanitary threats can, however, compromise the realization of the expected genetic gain. Including pest resistance traits in the breeding programs may contribute to a sustainable protection. Here we quantified the variation in different components of resistance of Norway spruce to its main pest, the pine weevil Hylobius abietis. We followed insect damage in two large progeny trials (52 open-pollinated families with 100-200 individuals per family and trial) naturally infested by the pine weevil. Pine weevils damaged between 17 and 48% of the planted seedlings depending on the trial and year, and mortality due to weevil damage was up to 11.4%. The results indicate significant genetic variation in resistance to the pine weevil, and importantly, the variation was highly consistent across trials irrespective of contrasting incidence levels. Individual heritability estimates for the different components of seedling resistance were consistently low, but family heritabilities were moderate (0.53 to 0.81). While forward selections and breeding for higher resistance seem not feasible, backwards selections of the best parent trees emerge as a putative alternative to reduce weevil damage. A positive genetic correlation between early growth potential and probability of being attacked by the weevil was also observed, but the relationship was weak and appeared only in one of the trials. Overall, results presented here open the door to a new attractive way for reducing damage caused by this harmful pest.

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