The Living Ash Project aims to identify a large and diverse number of ash trees with good tolerance to ash dieback, to secure this material for further breeding work, and to quickly make this material available to industry.  Trees that are selected will be further screened for tolerance in two different ways, via chemical fingerprinting and directly through controlled inoculations.

Managing Research Trials
Forest Research

Fourteen provenance trials were planted by Forest Research in 2012 to screen ash trees for tolerance to ash dieback.  Seven of these have now closed, and tolerant trees have been grafted and are in the National Archive.  Forest Research continue to monitor the other sites and the most tolerant selections will be added to the archive. In additional to these mass screening trials, Forest Research planted three progeny trials in 2014 from known parents to investigate heritability of tolerance.  These trials are ongoing.

The National Archive of Tolerant Material
Future Trees Trust

Between the Living Ash Project and the mass screening trials, almost 1000 trees displaying a high level of tolerance to ash dieback were selected and grafted in January 2018.  These were planted out on the public forest estate in December 2019 in the National Archive of Tolerant Ash and we continue to monitor these.  Some are not robust selections, and these will be removed over time, with trees with greater tolerance added.  As the disease progresses in Britain, trees with greater tolerance will become more obvious as ash trees decline and die.  We want you to tell us about these trees in any woodland you manage.

Testing the selections through LC-MS
Fera

Liquid chromatography mass spectrometry (LC-MS) has been shown to be a useful tool to quantify tolerance within trees through chemical screening.  It indicates changes in compounds, tentatively identified as iridoid glycosides, which are involved in herbivory defence.  A test panel is created using trees of know phenotype (we select 50 trees with high tolerance and 50 trees with very low tolerance).  We will then use the test panel to corroborate the tolerance selections made for the National Archive.

Testing the selections through controlled inoculation
Forest Research

Another method to test the tolerance of the selections made is through controlled inoculations.  Two methods will be tested: 1) Ascospores will be harvested from fruiting bodies and inoculated on to ash leaves and 2) small cubes of sterile ash wood will be inoculated with the fungus and taped to the main stem of the ash tree following the creation of a small wound. The infected trees will be monitored for several months and any resulting infections recorded.

Developing vegetative propagation techniques
Kew

The trees in the National Archive are grafted on to rootstocks of common ash. This is because grafting yields very high success rates (over 95%).  However, there is no guarantee that the rootstock is of tolerant material, and research has shown that ash can be infected through pores in the stem/ bark called lenticles, particularly when inoculum levels are high.  It is preferable to have tolerant selections on their own roots to eliminate this step.  Work in the original project looked at tissue culture, but costs are expensive and while getting plantlets from seed was straight forward, less success was obtained with shoot material. Here we will investigate vegetative propagation techniques for ash, to yield consistently high results which currently is hard to achieve without grafting.