Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2016
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Forfattere
Mari Mette Tollefsrud Tor Myking Jørn Henrik Sønstebø Vaidotas Lygis Ari Hietala Myriam HeuertzSammendrag
During post glacial colonization, loss of genetic diversity due to leading edge effects may be attenuated in forest trees because of their prolonged juvenile phase, allowing many migrants to reach the colonizing front before populations become reproductive. The northern range margins of temperate tree taxa in Europe are particularly suitable to study the genetic processes that follow colonization because they have been little affected by northern refugia. Here we examined how post glacial range dynamics have shaped the genetic structure of common ash (Fraxinus excelsior L.) in its northern range compared to its central range in Europe. We used four chloroplast and six nuclear microsatellites to screen 42 populations (1099 trees), half of which corresponded to newly sampled populations in the northern range and half of which represented reference populations from the central range obtained from previously studies. We found that northern range populations of common ash have the same chloroplast haplotypes as south-eastern European populations, suggesting that colonization of the northern range took place along a single migration route, a result confirmed by the structure at the nuclear microsatellites. Along this route, diversity strongly decreased only in the northern range, concomitantly with increasing population differentiation and complex population substructures, a pattern consistent with a leading edge colonization model. Our study highlights that while diversity is maintained in the central range of common ash due to broad colonizing fronts and high levels of gene flow, it profoundly decreases in the northern range, where colonization was unidirectional and probably involved repeated founder events and population fluctuations. Currently, common ash is threatened by ash dieback, and our results on northern populations will be valuable for developing gene conservation strategies.
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The root rot pathogens in Norway spruce (Picea abies) Heterobasidion ssp. cause substantial loss in carbon sequestered in forest and economic revenue for forest owners. To facilitate strategic breeding planning for increased resistance against this pathogen in particular, the blue stain fungus Endoconidiophora polonica, growth and wood quality traits (wood density and spiral grain), we estimated additive genetic parameters, correlations and the potential response from selection. Parameters were estimated from a progeny trial series established at two sites (25 years from planting) and their parents in a seed orchard (43 years from grafting). A standard half-sib analysis based on progenies and a parent–offspring regression was used for estimation of heritabilities. Resistance against the pathogens was measured as lesion length under bark after inoculations in phloem. Heritability values varied with site and estimation procedure from 0.06 to 0.33, whereas the phenotypic variance (as CV P ) is high and fairly stable around 40–50 %. Heritability values for wood density and spiral grain in the same material varied from 0.32 to 0.63. The highest heritability values were generally obtained from parent–offspring regression. There is no evidence of resistance traits being genetically correlated with growth or wood quality traits. Wood density is negatively correlated with stem diameter. Implications for breeding are discussed.
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Microsatellite markers are one of the most valuable genetic marker because of high polymorphism, codominant, high reproducibility and relatively high abundance in the genome. Classical techniques to identify and to develop microsatellite markers are time-consuming and require cloning and library construction followed by Sanger sequencing. In the recent years Next Generation Sequencing (NGS) have been widely used to identify molecular markers for non-model organisms. To test the efficiency of NGS techniques in developing molecular markers, we have used double digest Restriction site Associated DNA Sequencing (ddRADseq) to identify microsatellites in Heracleum. Genomic DNA from three individuals digested with SbfI and NdeI followed by size selection and library construction and then DNA fragments were sequenced with Ion Torrent PGM. After trimming adaptors and evaluating the quality of reads, QDD software was used to screen reads with microsatellite motives containing two, three, four, five and six nucleotide repeats. Almost 2% of all sequences were consisted microsatellites repeats. Fifty four singleton and consensus sequences were bioanformatically confirmed and were checked for contamination and similarity with NCBI nucleotide database. Seventy percent of the sequences were represented by (AT)n, (AT)n, (GA)n and (AC)n motives. Twenty five primer pairs were selected to test for amplification and the results showed that most of the loci produced the expected size on Agarose gel. Our results show the high efficiency of ddRADseq in developing sufficient number of markers in a short time where the budget is also limited. Keywords: Microsatellites, Next Generation Sequencing, ddRADseq, Heracleum
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Forfattere
Mari Mette TollefsrudSammendrag
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