Development of ash tree genetic resources
Developing ash tree genetic resources with tolerance to ash dieback and breeding technologies
Since 2015, Teagasc has developed two research projects on ash dieback of common ash (Fraxinus excelsior). This invasive tree disease was detected in Ireland in 2012 for the first time, likely after being introduced with imported ash planting stock from continental Europe. The disease will affect all ash trees in Ireland, causing the majority of them to die over the next two decades.
A very small proportion of ash trees show natural tolerance to the pathogen. This means that they show minor symptoms and the disease does not have noticeable impact on their growth or health.
Teagasc works to identify such trees and build up a gene bank with the ultimate goal of producing tolerant ash seed and restore ash trees to Irish forests and hedgerows.
Tolerant gene bank
The project aims to build a gene bank of ash composed by individual genotypes of ash with tolerance to ash dieback. These genotypes will be used to bulk up stocks of tolerant trees, as well as for establishing seed-producing orchards.
See image below: Dr Miguel Gorriz inoculates artificially an ash tree with H. fraxineus.
Importation of tolerant genotypes
We are establishing a collection of tolerant genotypes of ash by importing tolerant material from different ash breeding programmes in Europe. To date, Teagasc has built a collection of 200 tolerant genotypes. Multiple copies of each genotype have been produced by grafting.
See image below: Dr Gerry Douglas (retired from Teagasc), Brian Clifford (DAFM) and Mat Parratt (UK Forest Research) evaluate a putatively tolerant ash tree in a research plot.
Screening Irish ash abroad
We aim to identify tolerant individual trees by naturally screening Irish genotypes of ash in continental Europe where the disease is at a more advanced stage and disease pressure is higher. We are exposing 1000 Irish genotypes of ash to high disease pressure in infected areas in Lithuania to identify those trees that show no symptoms over a period of three years. These trees will be regarded as tolerant trees and included in the Irish ash gene bank.
See image below: Walsh Scholar Will Plumb samples ash seedlings in a woodland.
We aim to propagate vegetatively tolerant genotypes of ash in order to produce clones that can be planted in forests while tolerant seed is being produced and tested. Teagasc research aims to develop methods to scale up the propagation on a scale adaptable for commercial production.
Asiatic species of ash are numerous and several show resistance to ash dieback, having co-evolved with the pathogen in Asia. Controlled crossing of common ash with exotic ash species may be necessary as a means of introducing resistant genes. In this context, hundreds of artificial pollinations were done at Teagasc, 157 putative hybrids were produced, of which 14 were confirmed using genetic barcodes developed within the project. These hybrids will now be tested for their susceptibility to ash dieback and be included in a conservation collection.
The project works in close collaboration with Prof Richard Buggs (Queen Mary University London, UK) and a Teagasc PhD Walsh Scholar, William Plumb.
Other partners for screening trees for tolerance to ash dieback and sharing tolerant plant material include Prof Alfas Pliura (LAMMC, Lithuania), Dr Gustavo Lopez (Forest Research, UK), Dr Marijke Steenackers (INBO, Belgium), Dr Valentin Queloz (WSL, Switzerland), Dr Thomas Kirisits (BOKU, Austria), Dr Mateusz Liziniewicz (Skogforsk, Sweden) and Dr Arnaud Dowkiw (INRA, France).
The project collaborates with Coillte and OPW to establish multiple gene banks of tolerant ash across Ireland.
Nemesio-Gorriz, M., McGuinness, B., Grant, J., Dowd, L., & Douglas, G. C. (2019). Lenticel infection in Fraxinus excelsior shoots in the context of ash dieback. iForest-Biogeosciences and Forestry, 12(2), 160.
Plumb, William J., Timothy LR Coker, Jonathan J. Stocks, Paul Woodcock, Christopher P. Quine, Miguel Nemesio‐Gorriz, Gerry C. Douglas, Laura J. Kelly, and Richard JA Buggs. "The viability of a breeding programme for ash in the British Isles in the face of ash dieback." Plants, People, Planet 2, no. 1 (2020): 29-40.
Stocks, Jonathan J., Carey L. Metheringham, William J. Plumb, Steve J. Lee, Laura J. Kelly, Richard A. Nichols, and Richard JA Buggs. "Genomic basis of European ash tree resistance to ash dieback fungus.” Nature ecology & evolution 3, no. 12 (2019): 1686-1696.
Sollars, Elizabeth S. A., Andrea L. Harper, Laura J. Kelly, Christine M. Sambles, Ricardo H. Ramirez-Gonzalez, David Swarbreck, Gemy Kaithakottil, Endymion D. Cooper, Cristobal Uauy, Lenka Havlickova, Gemma Worswick, David J. Studholme, Jasmin Zohren, Deborah L. Salmon, Bernardo J. Clavijo, Yi Li, Zhesi He, Alison Fellgett, Lea Vig McKinney, Lene Rostgaard Nielsen, Gerry C. Douglas, Erik Dahl Kjær, J. Allan Downie, David Boshier, Steve Lee, Jo Clark, Murray Grant, Ian Bancroft, Mario Caccamo & Richard J. A. Buggs. "Genome sequence and genetic diversity of European ash trees." Nature 541, no. 7636 (2017): 212-216.
- See also: Ash dieback for further information on this tree disease.