Project description:European common ash, Fraxinus excelsior L., is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus we performed untargeted metabolomic profiling on leaves from selected F. excelsior individuals showing strong tolerance or susceptibility to H. fraxineus. We identified sets of "features" [small molecules] that enabled strong discrimination between tolerant or susceptible genotypes of F. excelsior. Strikingly, tolerant F. excelsior lines exhibited low levels of iridoid glycosides, known anti-feeding deterrents. As Europe is threatened by Emerald Ash Borer (Agrilus planipennis), an invasive wood boring beetle native to East Asia that has devastated North American ash, our study raises the question whether selection for resistance to H. fraxineus leads to ecological trade-offs that result in susceptibility to emerging pests such as emerald ash borer.
Project description:A de novo 454-Illumina whole genome sequence for a self-pollinated progeny of a Fraxinus excelsior tree growing in woodland in Gloucestershire, UK
Project description:BackgroundKnowledge of genetic structure and the factors that shape it has an impact on forest management practices. European ash (Fraxinus excelsior L.) has declined dramatically throughout its range as a result of a disease caused by the fungus Hymenoscyphus fraxineus. Despite the need for conservation and restoration of the species, genetic data required to guide these efforts at the country level are scarce. Thereofore, we studied the chloroplast and nuclear genetic diversity of 26 natural common ash populations (1269 trees) in Poland.ResultsChloroplast polymorphisms grouped the populations into two geographically structured phylogenetic lineages ascribed to different glacial refugia (the Balkans and the Eastern Alps). However, the populations demonstrated high genetic diversity (mean AR = 12.35; mean Ho = 0.769; mean He = 0.542) but low differentiation based on nuclear microsatellites (FST = 0.045). Significant spatial genetic structure, consistent with models of isolation by distance, was detected in 14 out of 23 populations. Estimated effective population size was moderate-to-high, with a harmonic mean of 57.5 individuals per population.ConclusionsGenetic diversity was not homogeneously distributed among populations within phylogenetic gene pools, indicating that ash populations are not equal as potential sources of reproductive material. Genetic differences among populations could be related to their histories, including founder effects or gene flow between evolutionary lineages (admixture). Our results suggest that ash stands across Poland could be treated as two main management units (seed zones). Therefore, despite the homogenizing effect of pollen gene flow known for this species, the genetic structure should be taken into account in the management of the genetic resources of the common ash. Although ash dieback poses an additional challenge for the management of genetic resources, efforts should be directed towards protecting populations with high genetic diversity within defined phylogenetic units, as they may be an important source of adaptive variation for future stands.
Project description:European ash, Fraxinus excelsior is facing the double threat of ongoing devastation by the invasive fungal pathogen, Hymenoscyphus fraxineus and the imminent arrival of the non-native emerald ash borer (EAB), Agrilus planipennis. The spread of EAB which is currently moving westwards from European Russia and Ukraine into central Europe, poses an additional substantial threat to European ash, F. excelsior. While the molecular basis for resistance or variation in resistance among European ash genotypes is heavily investigated, comparatively little is known about the molecular ash traits involved in resistance against EAB. In this study we have gathered transcriptomic data from EAB inoculated genotypes of F. excelsior that have previously shown different levels of susceptibility to EAB. Resultant datasets show differential gene expression in susceptible and resistant genotypes in response to EAB infestation. This data will provide important information on the molecular basis of resistance to the EAB and allow the development of management plans to combat a pending threat of a culturally and ecologically important European tree species.
Project description:Whereas most of the research on phloem loading is performed on herbaceous plants, less is known about phloem loading strategies in trees. In this study, the phloem loading mechanisms of Quercus robur and Fraxinus excelsior were analysed. The following features were examined: the minor vein structure, the sugar concentrations in phloem sap by the laser-aphid-stylet technique, the distribution of photoassimilates in the mesophyll cells by non-aqueous fractionation, gradients of sugar concentrations and osmotic pressure, and the expression of sucrose transporters. The minor vein configurations of Q. robur and F. excelsior belong to the open type. Quercus robur contained companion cells in the minor veins whereas F. excelsior showed intermediary cells in addition to ordinary companion cells. The main carbon transport form in Q. robur was sucrose (~1M). In F. excelsior high amounts of raffinose and stachyose were also transported. However, in both tree species, the osmolality of phloem sap was higher than the osmolality of the mesophyll cells. The concentration gradients between phloem sap and the cytoplasm of mesophyll cells for sucrose were 16-fold and 14-fold for Q. robur and F. excelsior, respectively. Independent of the type of translocated sugars, sucrose transporter cDNAs were cloned from both species. The results indicate that phloem loading of sucrose and other metabolites must involve active loading steps in both tree species. Quercus robur seems to be an apoplastic phloem loader while F. excelsior shows indications of being a symplastic or mixed symplastic-apoplastic phloem loader.
Project description:This data set is downloaded from MetaboLights (http://www.ebi.ac.uk/metabolights/) accession number MTBLS372 Abstract:European common ash, Fraxinus excelsior L., is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus we performed untargeted metabolomic profiling on leaves from selected F. excelsior individuals showing strong tolerance or susceptibility to H. fraxineus. We identified sets of “features” [small molecules] that enabled strong discrimination between tolerant or susceptible genotypes of F. excelsior. Strikingly, tolerant F. excelsior lines exhibited low levels of iridoid glycosides, known anti-feeding deterrents. As Europe is threatened by Emerald Ash Borer (Agrilus planipennis), an invasive wood boring beetle native to East Asia that has devastated North American ash, our study raises the question whether selection for resistance to H. fraxineus leads to ecological trade-offs that result in susceptibility to emerging pests such as emerald ash borer.