Introduction to our ‘Guest Blog’ below (by Shelagh McCartan)
In Europe, ash (Fraxinus) species are under threat from an emerging disease caused by the fungus Hymenoscyphus fraxineus. Ash dieback (also known as Chalara) is characterised by leaf loss, bark lesions, and crown dieback and is often fatal particularly in young trees. In Britain, the first report of ash dieback was in 2012, but it has since been recorded at over 1000 sites. As a result, there is a ban on the movement of live ash material. Dr Jo Clark, Forestry Research Manager for Earth Trust, has been involved in breeding broadleaved trees including ash (Fraxinus excelsior) for several years. I thought it would be interesting to have a tree breeder’s perspective on the implication of this serious pathogen on ash seed orchards and future breeding programmes.
Guest Blog by Dr Jo Clark (Forestry Research Manager, Earth Trust, UK)
In the UK, The Future Trees Trust, Earth Trust and Forest Research have been working on improving the quality of ash trees for timber for over 20 years. We started with the selection of superior phenotypes from across the UK, collected seed from them and raised them in a nursery as half sib families. These were planted out in replicated field trials across four sites and the trees assessed over 15 years to identify which families performed best in terms of form (apical dominance, branching habit) and vigour (height and diameter increment). Some families performed well across all sites, and others badly across all sites, and as might be expected, other families performed well to a variable degree across sites. After thinning approximately two thirds of the poorest families, we achieved tested status under the Forest Reproductive Material Regulations (FRM regs) with genetic gains in the region of 8%. This is the highest category of FRM and the first tested seed for a broadleaved tree available in the UK. The first seed year after thinning was 2012, the year ash dieback officially arrived in the UK and a ban on movement of live ash material was put in place.
So what now? The partners, along with the Sylva Foundation, have started a five year work programme called The Living Ash Project to screen the various categories of FRM to identify 400 trees that show a degree of tolerance to ash dieback from which to start a new breeding programme. Evidence on the continent indicates that about 1% of trees show a good degree of tolerance (less than 10% crown dieback) to Chalara. We are using the help of citizen science to screen ash trees that are in woodland in the UK and of the lowest category of FRM – source identified. However, as tree breeders and foresters, it’s important to us that a number of trees that pass the screening process are of good timber quality so we are screening all our ash resources of which we have over 40,000 trees in trials and orchards. We have stratified the seed that was collected from the tested orchard, and these will be planted out in field trials in winter 2015 in areas of high infection.
We would love for you to get involved. You can help us find tolerant trees from right across the UK. We are using Ashtag (a mobile app for your smartphone) to tag trees which are entered in to a database. You can obtain FREE tree tags from the Sylva Foundation which includes full instructions of what you need to do to help, available from the project website.