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Bringing back the ashes – overcoming ash dieback disease in the UK

Principal Supervisor: Professor Murray Grant, School of Life Sciences

Co-supervisor: Dr Lijiang Song (Chemistry)

PhD project title: Bringing back the ashes – overcoming ash dieback disease in the UK.

University of Registration: University of Warwick

Project outline:

Ash dieback (ADB), caused by the invasive fungus Hymenoscyphus fraxineus (Hf), has been a destructive disease of European ash (Fraxinus excelsior) since 1992 and was first seen in the UK in 2012. More than 100 million UK ash trees are threatened by this devastating fungal pathogen that has already killed > 1 million of trees across Europe. This epidemic has serious implications for the ecological role of ash as a keystone species in nature, its economic value as timber, and its service value in landscaping and ecosystem functions such as restriction of flooding. While most trees in heavily affected areas are severely damaged, fortunately, a small minority are clearly less susceptible.

Because there is extensive genetic heterogeneity between ash trees, we focissed our research on metabolomics – looking at small molecules and their role in ADB disease. We hypothesised that ash trees had pre-formed chemical defences to ADB.

Using untargeted profiling of Danish ash trees (because the disease had been there longer, and hence they had identified resistant trees) we identified some metabolites that discriminated ADB tolerant ash from susceptible ash. Unexpectedly, we found a class of secondary metabolites which were more abundant in ADB susceptible trees, than resistant trees (see Sollars et al. 2017, Nature). This class of compounds were the plant specific iridoid glycosides (IG) that are well known to have medicinal properties. So, what is interesting about about iridoid glycosides?

Iridoid glycosides are insect feeding deterrents and in the USA an insect called the Emerald Ash Borer (EAB) is killing 10’s of millions of ash trees. So, if we breed ADB resistant ash (which will take decades!!!!), will they all succumb to EAB (it is already in Russia) when it eventually arrives in the UK)?

This project will, (i) characterise the diversity of iridiods in UK and European ash trees, (ii) contrast to those in ash species which are unaffected by either EAB and ADB and (iii) develop an assay for iridoid bioactivity on fungi and insect feeding.

BBSRC Strategic Research Priority: Food Security

Techniques that will be undertaken during the project:

  • Appropriate analytical sample preparation and extraction
  • Statistical experimental design
  • Mass spectrometry
  • Data analysis
  • Microbial culturing
  • Insect feeding experiments
  • Preparative HPLC and NMR

Contact: Professor Murray Grant, University of Warwick