|dc.identifier.citation||Sollars, E. 2017. The genome and epigenome of the European ash tree (Fraxinus excelsior). Queen Mary University of London||en_US
|dc.description.abstract||European ash trees (Fraxinus excelsior ) are under threat from the fungal pathogen Hy-
menoscyphus fraxineus causing ash dieback disease (ADB). Previous research has shown
heritable variation in ADB susceptibility in natural ash populations. Prior to this project,
very little genetic data were available for ash, thus hampering efforts to identify markers
associated with susceptibility. In this thesis, I have presented nuclear and organellar assemblies of the 880 Mbp F. excelsior genome, with a combined N50 scaffold size of over 100
kbp. Using Ks distributions for six plant species, I found evidence for two whole genome
duplication (WGD) events in the history of the ash lineage, one potentially shared with
olive (Ks 0.4), and one potentially with other members of the Lamiales order (Ks 0.7).
Using a further 38 genome sequences from trees originating throughout Europe, I found
little evidence of any population structure throughout the European range of F.excelsior,
but nd a substantial decrease in effective population size, both in the distant (from 10
mya) and recent past. Linkage disequilibrium is low at small distances between loci, with an
r2 of 0.15 at a few hundred bp, but decays slowly from this point. From whole genome DNA
methylation data of twenty F. excelsior and F. mandshurica trees, I identi ed 665 Differ-
entially Methylated Regions (DMRs) between those with high and low ADB susceptibility.
Of genes putatively duplicated in historical WGD events, an average of 25.9% were differen-
tially methylated in at least one cytosine context, possibly indicative of unequal silencing.
Finally, I found some variability in methylation patterns among clonal replicates (Pearson's
correlation coefficient 0.960), but this was less than the variability found between different
genotypes ( 0.955). The results from this project and the genome sequence especially, will
be valuable to researchers aiming to breed or select ash trees with low susceptibility to ADB.||en_US
|dc.description.sponsorship||EU FP7-PEOPLE project `INTERCROSSING', ID:289974.
Sequencing of the reference tree was funded by NERC emergency grant NE/K01112X/1.||en_US
|dc.publisher||Queen Mary University of London||en_US
|dc.rights||The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author||
|dc.subject||Biological and Chemical Sciences||en_US
|dc.subject||European ash tree||en_US
|dc.subject||ash dieback disease||en_US
|dc.title||The genome and epigenome of the European ash tree (Fraxinus excelsior)||en_US