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Natural phenological variation in aspen (Populus tremula): the SwAsp collection
INFIVE, UNLP-CONICET, La Plata, Argentina.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).ORCID iD: 0000-0002-9337-4540
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).ORCID iD: 0000-0002-6002-929X
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2008 (English)In: Tree Genetics & Genomes, ISSN 1614-2942, Vol. 4, 279-292 p.Article in journal (Refereed) Published
Abstract [en]

The genus Populus is currently the main model system for genetic, genomic, and physiological research in trees. Phenotypic variation in aspen (Populus tremula) populations growing in different environments across Sweden is expected to reflect genetic variation that is important for local adaptation. To analyze such natural phenotypic and genetic variation, the Swedish Aspen (SwAsp) Collection was established. Trees were taken from 12 different populations across Sweden, from 56° to 66° latitude north and planted in two common gardens in Ekebo (55.9°N) and Sävar (63.4°N). Data related to phenological and growth traits were collected during the second year of growth. Some traits like the date of bud set and leaf area duration showed strong clinal variation patterns with latitude in both field trials, but the date of bud flush did not change along a latitudinal cline. The phenological traits showed moderate within-populations heritabilities, although growth traits showed weaker clinal patterns and lower heritabilities than the phenological traits. This research forms the starting point for the development of the SwAsp collection, a resource facilitating analysis of the natural genetic variation in aspen, the elucidation of the structure and dynamics of aspen populations, and the future identification of the genes controlling adaptive traits using association mapping of selected candidate genes.

Place, publisher, year, edition, pages
SpringerLink , 2008. Vol. 4, 279-292 p.
Keyword [en]
Populus tremula, Natural variation, Phenology
URN: urn:nbn:se:umu:diva-11481DOI: 10.1007/s11295-007-0108-yOAI: diva2:151152
Available from: 2009-01-09 Created: 2009-01-09 Last updated: 2015-04-29Bibliographically approved
In thesis
1. Tracing selection and adaptation along an environmental gradient in Populus tremula
Open this publication in new window or tab >>Tracing selection and adaptation along an environmental gradient in Populus tremula
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The distribution of the expressed genotype is moved around in the population over time byevolution. Natural selection is one of the forces that act on the phenotype to change the patterns ofnucleotide variation underlying those distributions. How the phenotype changes over aheterogeneous environment describes the type of evolutionary force acting on this trait and thisshould be reflected in the variation at loci underlying this trait. While the variation in phenotypesand at the nucleotide level in a population indicates the same evolutionary force, it does notnecessarily mean that they are connected. In natural populations the continuous shifting of geneticmaterial through recombination events break down possible associations between loci facilitates theexamination of possible causal loci to single base pair differences in DNA-sequences. Connecting thegenotype and the phenotype thus provides an important step in the understanding the geneticarchitecture of complex traits and the forces that shape the observed patterns.This thesis examines the European aspen, Populus tremula, sampled from subpopulations overan extensive latitudinal gradient covering most of Sweden. Results show a clear geneticdifferentiation in the timing of bud set, a measure of the autumnal cessation of growth, betweendifferent parts of Sweden pointing at local adaptation. In the search for candidate genes thatunderlie the local adaptation found, most genes (25) in the photoperiodic gene network wereexamined for signals of selection. Genes in the photoperiodic network show an increase in theheterogeneity of differentiation between sampled subpopulations in Sweden. Almost half (12) of theexamined genes are under some form of selection. Eight of these genes show positive directionalselection on protein evolution and the gene that code for a photoreceptor, responsible for mediatingchanging light conditions to downstream targets in the network, has the hallmarks of a selectivesweep. The negative correlation between positive directional selection and synonymous diversityindicates that the majority of the photoperiod gene network has undergone recurrent selectivesweeps. A phenomenon that likely has occurred when P. tremula has readapted to the northern lightregimes during population expansion following retracting ice between periods of glaciations. Two ofthe genes under selection also have single nucleotide polymorphisms (SNP) that associate with budset, two in the PHYB2 gene and one in the LHY2 gene. Furthermore, there is an additional SNP inLHY1 that explain part of the variation in timing of bud set, despite the lack of a signal of selection atthe LHY1 gene. Together these SNPs explain 10-15% of the variation in the timing of bud set and 20-30% more if accounting for the positive co-variances between SNPs. There is thus rather extensiveevidence that genes in the photoperiod gene network control the timing of bud set, and reflect localadaptation in this trait.

Place, publisher, year, edition, pages
Umeå: Institutionen för Ekologi, miljö och geovetenskap, Umeå universitet, 2009. 42 p.
Local adaptation, Selection, genetic differentiation, QST, FST, Association study, frequency spectra, recurrent hitchhiking, selective sweep, Tree, Populus, natural selection, quantitative genetics
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Research subject
Population Biology; Genetics
urn:nbn:se:umu:diva-30123 (URN)978-91-7264-907-1 (ISBN)
Public defence
2010-01-16, Stora Hörsalen KBC, KB3B1, Umeå Universitet, KBC, Linnaeus väg 6, Umeå, 10:00 (English)
Available from: 2009-12-17 Created: 2009-12-07 Last updated: 2010-02-01Bibliographically approved

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Hall, DavidAlbrectsen, BenedicteKarlsson, JanIngvarsson, PärJansson, Stefan
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Department of Ecology and Environmental SciencesDepartment of Plant PhysiologyUmeå Plant Science Centre (UPSC)

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