ENVIRONMENTAL MICROBIOLOGY Fungal Assemblages Associated with Roots of Halophytic and Non-halophytic Plant Species Vary Differentially Along a Salinity Gradient Jose G. Maciá-Vicente & Valeria Ferraro & Santella Burruano & Luis V. Lopez-Llorca Received: 12 February 2012 / Accepted: 24 April 2012 # Springer Science+Business Media, LLC 2012 Abstract Structure of fungal communities is known to be influenced by host plants and environmental conditions. However, in most cases, the dynamics of these variation patterns are poorly understood. In this work, we compared richness, diversity, and composition between assemblages of endophytic and rhizospheric fungi associated to roots of two plants with different lifestyles: the halophyte Inula crithmoides and the non-halophyte I. viscosa (syn. Dittri- chia viscosa L.), along a spatially short salinity gradient. Roots and rhizospheric soil from these plants were collected at three points between a salt marsh and a sand dune, and fungi were isolated and characterized by ITS rDNA sequenc- ing. Isolates were classified in a total of 90 operational taxo- nomic units (OTUs), belonging to 17 fungal orders within Ascomycota and Basidiomycota. Species composition of en- dophytic and soil communities significantly differed across samples. Endophyte communities of I. crithmoides and I. viscosa were only similar in the intermediate zone between the salt marsh and the dune, and while the latter displayed a single, generalist association of endophytes, I. crithmoides harbored different assemblages along the gradient, adapted to the specific soil conditions. In the lower salt marsh, root assemblages were strongly dominated by a single dark septate sterile fungus, also prevalent in other neighboring salt marshes. Interestingly, although its occurrence was positively correlated to soil salinity, in vitro assays revealed a strong inhibition of its growth by salts. Our results suggest that host lifestyle and soil characteristics have a strong effect on endophytic fungi and that environmental stress may entail tight plant–fungus rela- tionships for adaptation to unfavorable conditions. Introduction Fungal endophytes can be found colonizing the tissues of all plants, irrespective of their taxonomical affiliation or envi- ronmental preferences. Several works point out that mutu- alistic interactions between plants and their associated fungal consortia are of paramount relevance for the distri- bution of plant communities worldwide, through increasing host fitness and assisting in adaptation to environmental and biological stresses [1–4]. Endophytic colonization of above- ground plant tissues may lead to beneficial effects to the host (e.g., [5]), for instance, in some grasses where Clavicipita- ceous endophytes (classified as class 1 endophytes in [6]) are responsible for herbivory resistance [7]. However, it is generally assumed that most plant–fungus mutualistic interactions take place in roots, due to a more systemic colonization [6, 8]. According to [6], such mutualisms involve endophytes within classes 2 and 4, in combination with a plethora of other symbionts such as mycorrhizae Electronic supplementary material The online version of this article (doi:10.1007/s00248-012-0066-2) contains supplementary material, which is available to authorized users. J. G. Maciá-Vicente (*) : L. V. Lopez-Llorca Multidisciplinary Institute for Environmental Studies (MIES) “Ramón Margalef,” Department of Marine Sciences and Applied Biology, University of Alicante, Apto. 99, 03080 Alicante, Spain e-mail: jgmv@ua.es V. Ferraro : S. Burruano Department DEMETRA, Università degli Studi di Palermo, Viale delle Scienze 2, 90128 Palermo, Italy Present Address: J. G. Maciá-Vicente U.S. Geological Survey, 6505 65th St NE, Seattle, WA 98115, USA Microb Ecol DOI 10.1007/s00248-012-0066-2