Development of ash tree genetic resources
Developing ash tree genetic resources with resistance to ash dieback (Chalara) and breeding technologies
A four year project has begun in 2014 on Chalara disease of common ash (Fraxinus excelsior). This dieback disease may become established in Ireland from residual stocks of imported trees which may carry infection as well as from wind borne spores.
The project aims to procure individual trees of ash which show resistance / tolerance to Chalara and use them to bulk up stocks of resistant trees vegetatively, as well as for establishing seed producing orchards with resistant parent trees. We aim to identify tolerant individual trees within existing provenance trials in infected areas abroad. In addition we plan to expose selected trees to high disease pressure by transfer of grafted and micro propagated trees into infected areas abroad so as to identify those trees which show no symptoms in the presence of Chalara spores. These will be regarded as Chalara tolerant trees. Vegetative copies of each tree will be retained in Ireland and will be used for developing methods to scale up the production of specific genotypes on a scale adaptable for commercial production.
Asiatic species of ash are numerous and several are shown to be resistant to Chalara, having co-evolved with the pathogen in Asia. We will determine the genetic diversity in gene banks of ash designated for breeding (Plus trees & European provenances), their phylogenetic relationships within F. excelsior and the identification of those species which are phylogenetically closest to F. excelsior. Controlled crossing of common ash with Asiatic species may be necessary as a means of introducing resistance genes from Asiatic species and will be undertaken.
The project works in close collaboration with Dr Richard Buggs, Queen Mary University of London and a Teagasc PhD Walsh Fellow.
Other partners for screening trees for resistance include Dr Arnaud Dowkiw, INRA Orleans, France and Dr Alfas Pliura, Forest Research Institute, Lithuania.