Endophyte community composition is associated with dieback occurrence in an invasive tree

Background and aims 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, Parkinsonia aculeata L. (parkinsonia). Methods 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. Results 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. Conclusions 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.