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Endophyte community composition is associated with dieback occurrence in an invasive tree
T. V. STEINRUCKEN (1), A. Bissett (2), J. R. Powell (1), A. K. H. Raghavendra (3), R. D. van Klinken (3). (1) Hawkesbury Institute for the Environment, University of Western Sydney, Penrith NSW, Australia; (2) CSIRO Agriculture Flagship, Canberra, Australia; (3) CSIRO Biosecurity Flagship, Brisbane, Australia

Dieback is pervasive in many populations of invasive woody weeds globally. Previous studies on dieback have focused on specific potential causative biotic agents, but most cases remain unexplained. The potential role of endophytic microbial communities in dieback, including the relative importance of endophytes with pathogenic or protective capabilities, remains poorly studied. We tested whether changes in archaeal, bacterial and fungal endophyte community structure is associated with dieback occurrence in the invasive, leguminous tree, <i>Parkinsonia aculeata </i>L. (parkinsonia). We sampled roots, stems and stem tips from healthy and dieback-affected parkinsonia and conducted terminal restriction fragment length polymorphism (T-RFLP) analysis on DNA extracted from these samples using domain-specific primers for archaea, bacteria and higher fungi. Microbial community composition strongly differed with parkinsonia disease status (archaea, bacteria and fungi) and plant part (archaea and fungi). Plant part and disease status effects were strongest in archaea. We also found evidence implicating both pathogenic and potentially protective endophytes in the onset of dieback. This is the first study that has shown significant associations between changes in endophyte community composition and dieback presence. Our results highlight the complexity of those changes and provide support for the hypothesis that diverse pathogenic and protective endophytes may be implicated in dieback.

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