Characterisation of above-ground endophytic and soil fungal communities associated with dieback-affected and healthy plants in five exotic invasive species Anil K.H. Raghavendra a, *, 1 , Andrew B. Bissett b, e, 1 , Peter H. Thrall b , Louise Morin c , Tracey V. Steinrucken a , Victor J. Galea d , Ken C. Goulter d , Rieks D. van Klinken a a CSIRO Health and Biosecurity, Ecosciences Precinct, Dutton Park, Queensland 4102, Australia b CSIRO Agriculture and Food, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia c CSIRO Health and Biosecurity, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia d School of Agriculture and Food Sciences, The University of Queensland, Gatton Campus, Gatton, Queensland 4343, Australia e CSIRO, Oceans and Atmosphere, Hobart 7000, Australia article info Article history: Received 30 May 2016 Received in revised form 15 December 2016 Accepted 10 January 2017 Available online 9 February 2017 Corresponding Editor: Barbara J. Schulz Keywords: Fungal community structure Latent pathogens Plant population decline Plant health ITS1 region 454 sequencing Weeds abstract In Australia, several well-established invasive plant species have experienced unexplained dieback. To investigate this issue, we used internal transcribed spacer (ITS) amplicon pyrosequencing to characterise fungal communities within stems (endophytes) and soils associated with dieback-affected and healthy plants from populations of five exotic invasive species (Jatropha gossypiifolia, Mimosa pigra, Parkinsonia aculeata, Tamarix aphylla and Vachellia nilotica) across northern Australia. M. pigra and P. aculeata were sampled from multiple geographic regions. A total of 353 and 4926 fungal operational taxonomic units (OTUs) were identified in stem and soil samples, respectively. Members of Ascomycota were common, representing 75% of stem and 49% of soil OTUs. Four common endophytes, including Cladosporium perangustum, were at least 50% more prevalent in healthy than dieback-affected samples for the five invasive species combined. Fungal community structure within stem and soil samples varied among invasive species. For the two species sampled across multiple regions, M. pigra had similar fungal communities within stems among regions, but a significant difference in associated soil fungi, suggesting that host plant rather than environment determined endophytic communities in this species. Irre- spective of the invasive species and sample type (stem vs. soil), no significant differences were observed in fungal richness, diversity or community structure between dieback-affected and healthy plants, either locally or regionally. Our work failed to identify fungi that were either unique or relatively more abundant in dieback than healthy plants in these invasive species. Future investigations of biotic factors other than fungi, such as bacteria, archaea and oomycetes, may provide more insights into the mecha- nism of the dieback phenomenon affecting these species. Crown Copyright © 2017 Published by Elsevier Ltd. All rights reserved. 1. Introduction There is an increasing number of cases globally where the plant health of well-established exotic invasive plant species has declined, subsequently resulting in at least local population re- ductions (Li et al., 2009; Boyce et al., 2014; Meyer et al., 2014). In Australia, this includes several of the most serious invaders, and has been observed across the geographic range of some of these (van Klinken and Heard, 2012; Aghighi et al., 2014). Despite this, we lack a clear understanding of the mechanisms that cause such decline, although it is speculated that biotic factors, such as fungi, oomycetes or bacteria, may play a critical role. It is becoming clear from a few recent studies that pathogens (particularly soil-borne) may be limiting recruitment in invasive plant populations (Nijjer et al., 2007; Diez et al., 2010; Dost al et al., 2013). However, we have limited knowledge of above- and/or below-ground microbial communities associated with deteriorating health of established invasive plants (Flory and Clay, 2013). Even for those studies where * Corresponding author. E-mail address: anil.raghavendra@hotmail.com (A.K.H. Raghavendra). 1 Anil K.H. Raghavendra and Andrew B. Bissett contributed equally to this work. Contents lists available at ScienceDirect Fungal Ecology journal homepage: www.elsevier.com/locate/funeco http://dx.doi.org/10.1016/j.funeco.2017.01.003 1754-5048/Crown Copyright © 2017 Published by Elsevier Ltd. All rights reserved. Fungal Ecology 26 (2017) 114e124