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SoCoBio (Universities of Southampton, Kent, Sussex, Portsmouth and NIAB EMR)

What turns a saprophyte into pathogen: the case of Ash dieback

Dr Matevz Papp-Rupar, Project leader, NIAB EMR
Ian R. Brown, Manager of Microscopy facility, School of Biosciences, University of Kent
Dr Campbell W. Gourlay, Reader in Cell Biology, School of Biosciences, University of Kent

Project Summary

The Ash dieback pathogen Hymenoscyphus fraxineus is nothing more than a saprophyte on senescent leaves of the native Manchurian ash (Fraxinus mandshurica). When introduced in Europe however, it decimated European ash (F. excelsior) populations across the continent in only a few decades. Our studies indicate that H. fraxineus infects F. excelsior leaves in a hemi-biotrophic way which leads to extensive fungal growth in the wood and consequently dieback of infected branches. It is not known to what extent H. fraxineus colonises F. mandshurica leaves stems and branches and the type of lifestyle it lives in its native host. Is Manchurian ash keeping dieback off by strong preformed and induced defences? Is the lack of host cues responsible for switching on fungal infection programmes too early in the season resulting in dieback on European ash? This PhD project will combine genomic, cell biology and metabolomics approach to shed light on the many unknowns of this devastating pathogen. Importance of preformed and induced F. mandshurica and F. excelsior metabolites will be screened with ascospore and mycelial bioassays. Fluorescent and TEM microscopy will be used to reveal differences in penetration and colonisation in F. mandshurica and F. excelsior and also their cellular responses to H. fraxineus. Finally, predicted H. fraxineus secretome will be compares to H. albidus, closely related non-pathogen, and other hemi-biotrophic pathogens (Colletotrichum graminicola and Magnaporthe oryzae/grizea) to identify common and unique infection mechanisms to be confirmed by transcription in planta.