Towards protecting the UK landscape; a novel method to screen for resistance to ash dieback while mitigating herbivory tradeoffs.

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The UK' s track record in dealing with alien invasive pests and pathogens affecting our trees is poor, particularly when considering (i) the enormous volume of trade in plants and plant products and (ii) the environmental and societal impacts of tree pathogens. No case of tree diseases has a higher profile than ash dieback - the only plant disease that has resulted in the Government's emergency COBRA group meeting twice! Recent spates of tree diseases have highlighted and exposed some of the deficiencies in past biosecurity measures and funding for tree health (Woodward & Boa 2013). For example in his excellent book "The Ash Tree" Oliver Rackham (1939-2015) called for a radical change in our attitude towards trees and a revival in 'the science of pathology' which 'has been scandalously neglected in Britain'. But it is not just the need to improve plant pathology skills but to embrace state-of-the-art molecular technologies to make valuable contributions to tree biology in the UK and worldwide. Indeed has molecular technologies been applied to ADB earlier it may not have taken nearly 20 years to identify the causal agent of ADB as Hymenoscyphus fraxineus and not Hymenoscyphus albidus which was known to have exist in Europe for more than 150 years. As a consequence there was no possibility under EU law to restrict imports of ash trees to Britain. This proposal uses "metabolite profiling", a cutting edge molecular technology to help address ADB. We initially looked at the "metabolic profile" of tolerant and susceptible Danish ash, as the Danes have been battling ADB for more than 20 years. Using sophisticated equipment that can measure the "weight" of these small molecules we can make of list of their presence/absence and relative abundance in in tolerant and susceptible ash. Our work has looked at nearly ~20,000 such small molecules and identified several hundred that discriminate tolerant from susceptible ash. Of these at least 50-60 are really "discriminatory" and can be used to develop a method to look at British ash trees. However our work also discovered something totally unexpected. Some compounds that we know are involved in stopping insects eating plants were present in very low levels in tolerant ash compared to susceptible ash. Now this could be critically important. Why? We are currently committing millions of pounds towards selecting British ash with tolerance to ADB. However, any strategy for breeding British ash trees resistant to ADB will need to consider that they will be suitable food sources for emerald ash borer (Agrilus planipennis), a destructive jewel beetle native to China. Emerald ash borer has killed tens of millions of ash trees since its arrival in North America 20 years ago and has recently been reported 250 km west of Moscow. It is important to further investigate our preliminary data that suggest trees selected for resistance to ADB have very low levels these anti-feeding compounds, technically known as iridoid glycosides we may be unwittingly be selecting for enhanced susceptibility to emerald ash borer.This application is designed to build on these very recent findings that identified features which could discriminate between tolerant and susceptible Danish ash trees. We now seek funding to develop this methodology further and establish the necessary tools to: (i) discriminate tolerant and susceptible British ash germplasm by screening for specific small molecule signatures; (ii) determine whether low levels of these anti-herbivory compounds are intimately associated with tolerance to ash dieback (ADB) and; (iii) generate a detailed metabolome (small molecules existing in samples) of tolerant and susceptible British ash leaves. The ability to monitor metabolomics signatures of selected British ash dieback resistant germplasm can ensure selection programmes are not inadvertently selecting for susceptibility to Emerald Ash Borer.