You are here: Home  Research  Thematic area: Establishing and growing forests  ASHGEN
You are here: Home  Research  Thematic area: Establishing and growing forests  ASHGEN

ASHGEN

Identifying the scale of suspected hybrid ash in Ireland 

DOWNLOAD 2009 REPORT AS PDF (pdf 139Kb) 
DOWNLOAD REPORT IN IRISH (pdf 138Kb) 

PROJECT TEAM
Dr Gerry Douglas, Teagasc*
John Mc Namara, Teagasc
Dr Juan Fernandez, University of Paris
Dr Nathalie Frascaria, University of Paris
Dr Trevor Hodkinson, Trinity College Dublin
Muriel Thomasset, Trinity College Dublin and Teagasc

* Email: gerry.douglas@teagasc.ie

COMPLETION DATE: June 2010

BACKGROUND
Ash imported from 1993 to 2000 have produced poorly growing plantations in a substantial number of cases. This project investigates whether the planting stock was true common ash (Fraxinus excelsior) or natural hybrid material involving another continental species (F. angustifolia). These plantations are now seeding. The project is investigating the origin of the imported trees and their interbreeding capacity, as the dispersal of hybrid seed into the landscape may give rise to a wild population that would interbreed with native stock, resulting in genetic pollution of native ash germplasm.

OBJECTIVES
The overall objective is to provide a set of tests that can confirm the hybrid nature of ash that is present in suspect stands in Ireland and their potential  to interbreed with indigenous ash.
The specific objectives are:

  •     to examine suspect ash stands in Ireland using known morphological criteria;
  •     to examine suspect ash stands in Ireland using known molecular criteria;
  •     to assess the potential threat of confirmed hybrid material to introgress with native stocks of ash.

    PROGRESS
    Two sites, one in Dublin and one in Meath, have been chosen for intensive study as  well as material from France where natural hybridisation of ash occurs. Several tasks have been completed and data are being analysed. Completed studies include a comparison of flowering time (phenology) and the sex ratio of trees  in suspect 'hybrid' plantations and native  ash trees. Our studies have shown that flowering period of suspect hybrid ash in plantations can overlap with native trees and that seeds are produced in these plantations. By a paternity analysis of the seeds, we aim to determine whether the seeds were produced by pollen from within the stand of imported trees or by pollen from native trees around the stand. Similarly, we are examining seeds on native trees in hedgerows near these plantations to see if they were sired by pollen from the imported trees. DNA has been isolated from parent trees and statistical analyses of the morphological data, combined with the genetic data is underway to determine the paternity of the seeds collected in the suspect hybrid stands. This will also indicate the level of gene flow from plantation to native trees and from natives to plantation trees.
    Seeds collected from suspect hybrid trees have been stratified and are now in germination tests to compare the embryo size and plant development from these seeds compared to native ash. To determine those characters which may be diagnostic for hybrid ash we have studied F1 hybrid ash trees which were produced from controlled crosses. The parameters measured were the density of stomatal cells and leaf morphology traits. In addition, DNA has been extracted from parent and F1 hybrid trees and a molecular analysis is in progress.
    Work is underway to develop a 'bar code' approach to genotyping ash using molecular markers for potentially adaptive characters which could distinguish F. excelsior from F. angustifolia and hybrids; the genes involved affect foliar morphology, drought resistance, bud flushing, and dormancy.
    A set of guidelines have been drafted as an aid to identify hybrid ash. The features of hybrid ash are:
  •     Brown buds are associated with hybrid trees but black buds may are also found.
  •     Narrow leaflets, about 2 cm wide with a spear form, usually bearing between 7 to 15 conspicuous marginal teeth are typical of many hybrids. Common ash bears at least 20 very small teeth and frequently up to 30.
  •     Leaflet numbers on sun-exposed branches can be as low as 5, but more typically 7, although some branches can exhibit more leaflets; common ash exhibits frequently 9 to 13 leaflets.
  •     Tendency to produce leaf and bud whorls of three on the same plane especially on slow growing branchlets and twigs. This is also associated with a round, plump terminal bud in hybrids. Common ash typically has two opposite leaves with a `snake head pointed bud
  • .
  •     Flowering time in hybrid individuals usually starts earlier, (December-January); common ash tends to flower in mid February to March, or even April depending on climatic conditions during the year.

    ACTIVITIES PLANNED
  •     Sequencing of a comprehensive sample of Irish provenances, continental F. excelsior and F. angustifolia and hybrid populations using expressed sequence tags (ETS) and Internal Transcribed Spacers (ITS) to provide a potential `bar code approach
  • to identification.
  •     Analyses of paternity determination for progeny collected in hybrid plantations.
  •     Submit a scientific paper for publication on the characterization of F1 hybrid ash.
  •     Prepare a set of guidelines to aid in the identification of hybrid ash in a leaflet form, and guidelines on how best to mitigate and manage the problem in plantations.
  •     Determine the viability of seeds from Irish hybrid plantations.
  •     Complete the morphological analysis of Irish plantation material to compare with putative hybrid zone material from France.
  •     Complete the genetic fingerprinting (genotyping) of chloroplast markers for two plantations.

    OUTPUTS
    Posters
    Muriel Thomasset, Gerry Douglas, Trevor Hodkinson.  2008. Hybrid alien ash in Ireland and its potential for interbreeding with native ash. Postgraduate Ecology Forum conference 10-12 March 2008 at Trinity College Dublin. Conference book, page 40.
    Juan F. Fernández-M., Muriel Thomasset,  Trevor R. Hodkinson, Nathalie Frascaria-Lacoste, Gerry C. Douglas. 2008 Identifying the scale of suspected hybrid ash (F. excelsior × F. angustifolia) in Ireland and its potential for genetic pollution of indigenous ash. Climate Change and Systematics, 1-3 September 2008 at Trinity College Dublin. Conference book, page 24.
    Muriel Thomasset, Gerry Douglas, Trevor Hodkinson. 2008. Hybrid alien ash: F. excelsior × F. angustifolia and its potential for interbreeding with native ash under current and future climatic conditions. Climate Change and Systematics, 1-3 September, 2008 at Trinity College Dublin. Conference book, page 29.
    Juan F. Fernández-M.,  Muriel Thomasset,  Trevor R. Hodkinson, Nathalie Frascaria-Lacoste, Gerry C. Douglas. 2008. Identifying the scale of suspected hybrid ash (F. excelsior × F. angustifolia) in Ireland and its potential for genetic pollution of indigenous ash.  Agricultural Biotechnology International Conference August 24-28 2008, University College Cork. Poster 1.18 Book of abstracts, page 8.

    Communications
    'Keeping Irish ash pure'  2008. ScienceSpin No. 31 p10.
    M. Thomassett. Seminar day for first year postgraduate at Trinity College Dublin, 25 March 2008:   Presentation: 'Hybrid alien ash in Ireland and its potential for interbreeding with native ash.'
    M. Thomasset,  T. R. Hodkinson, G. C. Douglas. 2009. Assessing the potential for introgression of imported ash with native ash (Fraxinus excelsior L.) Irish Ag. Forum (in press).
    G.C. Douglas, M. Thomasset, T.R. Hodkinson.  2009. Phenology of alien hybrid ash Fraxinus excelsior × F. angustifolia in Ireland. Presentation at Treebreedex meeting Noble Hardwood Trees Breeding  Italy (in press).

    Report
    Muriel Thomasset. 2009. Transfer Report from MSc to PhD Programme at TCD. Hybrid alien ash: Fraxinus excelsior × F. angustifolia in Ireland and its potential for interbreeding with native ash.
     

     

    download 2008 report as pdf (pdf 177Kb)  

    2008 REPORT

    PROJECT TEAM
    Dr Gerry Douglas, Teagasc*
    John Mc Namara, Teagasc
    Dr Juan Fernandez, University of Paris
    Dr Nathalie Frascaria, University of Paris
    Dr Trevor Hodkinson, Trinity College Dublin
    Muriel Thomasset, Trinity College Dublin and Teagasc
    * Email: gerry.douglas@teagasc.ie

    COMPLETION DATE: June 2010

    BACKGROUND
    Ash plants imported from 1993 to 2000 have produced poorly growing plantations in a substantial number of cases. This project investigates whether the planting stock was true common ash (Fraxinus excelsior) or natural hybrid material involving another continental species (F. angustifolia). These plantations are now seeding. The project is investigating the origin of the imported trees and their interbreeding capacity because the dispersal of hybrid seed into the landscape may give rise to a wild population that would interbreed with native stock, resulting in genetic pollution of native ash germplasm.

    OBJECTIVES
    The overall objective of this research is to provide a set of tests that can confirm the hybrid nature of ash that is present at suspect sites in Ireland and the potential of these plantations to interbreed with indigenous ash.
    The specific objectives are:

  • to examine suspect material in Ireland using known morphological criteria;
  • to examine suspect material in Ireland using known molecular criteria;
  • to assess the potential threat of the confirmed hybrid material to further introgress with native stocks of ash.

    PROGRESS
    Fourteen suspect plantations were examined and four of these were intensively sampled to study morphology and molecular markers in Meath, Wicklow, Kerry and Dublin, as well as aterial from control populations in France.
    Morphological features of the leaves from three sites did not fit well with the set of characters that were found in pure control populations of either F. excelsior or F. angustifolia.
    The lack of significant clustering of the Irish plantation ash with either control population from France may indicate that these controls may not be the most appropriate to use.
    Hybridisation of ash is known in several regions of France and control populations from other areas may give more useful information. Furthermore, the results showed that material in two of the plantations share more characters with each other than with either species. This suggests that the source of the plantation ash may be from the same or nearby regions of provenance.
    Molecular analysis of single gene markers were equivocal but indicated a strong component of F. angustifolia. Several features including 11 morphological and 13 molecular markers were examined using multivariate statistics. For the Irish samples it showed that most of the trees indicated a hybrid nature (Meath and Kerry) while those in Wicklow were very close to F. angustifolia. However, morphological characters of F. angustifolia were only apparent in certain individuals, suggesting the cryptic hybrid nature of many trees.
    At each plantation site the onset of flowering was earlier among the plantation trees compared to native surrounding trees. This is more characteristic of F. angustifolia and it may be a useful practical indicator of hybridity. Over 60% of the plantation trees at two sites produced some flower buds and we found an overlap in the flowering periods of plantation trees with native trees that leaves the possibility of hybridisation and gene flow from plantations to native trees and visa versa.

    ACTIVITIES PLANNED
  • Complete the genetic fingerprinting (genotyping) of chloroplast markers for two plantations.
  • Genotyping of 96 trees from Clonee with 12 nuclear and chloroplast microsatellite markers and of the progeny (seeds) to determine the sources of pollen (from within the plantation or from outside).
  • Complete the morphological analysis of Irish plantation material to compare with putative hybrid zone material from France.
  • Cloning and sequencing of more trees to produce specific primers for the ETS to provide a potential `bar code approach
  • to identification.
  • Determine the viability of seeds from Irish hybrid plantations.

    OUTPUTS
    Muriel Thomasset wrote a paper on Hybridisation, introgression and climate change: a case study in the tree genus Fraxinus, for a book published by the Systematics Association and Cambridge University Press.

    Posters
    Muriel Thomasset, Gerry Douglas, Trevor Hodkinson. 2008. Hybrid alien ash in Ireland and its potential for interbreeding with native ash. Postgraduate Ecology Forum conference 10- 12 March 2008, Trinity College Dublin. Conference book p40.
    Juan F. Fernández-M., Muriel Thomasset, Trevor R. Hodkinson, Nathalie Frascaria-Lacoste, Gerry C. Douglas. 2008. Identifying the scale of suspected hybrid ash (F. excelsior × F. angustifolia) in Ireland and its potential for genetic pollution of indigenous ash. Climate Change and Systematics, 1-3 September 2008, Trinity College Dublin. Conference book p24.
    Muriel Thomasset, Gerry Douglas, Trevor Hodkinson. 2008. Hybrid alien ash: F. excelsior × F. angustifolia and its potential for interbreeding with native ash under current and
    future climatic conditions. Climate Change and Systematics, 1-3 September 2008, Trinity College Dublin. Conference book p29.
    Juan F. Fernández-M., Muriel Thomasset, Trevor R. Hodkinson, Nathalie Frascaria-Lacoste, Gerry C. Douglas. 2008. Identifying the scale of suspected hybrid ash (F. excelsior × F. angustifolia) in Ireland and its potential for genetic pollution of indigenous ash. Agricultural Biotechnology International Conference, 24-28August 2008, University College Cork. Poster 1.18 Book of abstracts p8.

    Communications
    Douglas, G. Keeping Irish ash pure. 2008. Science Spin No. 31 p10.
    Thomasset, M. Hybrid alien ash in Ireland and its potential for interbreeding with native ash. Seminar day for first year postgraduates at Trinity College Dublin, 25 March 2008.

    Conference presentations
    Postgraduate Ecology Forum conference, 10-12March 2008, Trinity College Dublin.
    Ecological Genetics Group (EGG) conference, 1-3 April 2008, University of Sheffield, England.
    Climate Change and Systematics, 1-3 September 2008, Trinity College Dublin.