ORIGINAL PAPER Soil moisture—a regulator of arbuscular mycorrhizal fungal community assembly and symbiotic phosphorus uptake Sharma Deepika & David Kothamasi Received: 13 May 2014 /Accepted: 7 July 2014 /Published online: 2 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Multiple species of arbuscular mycorrhizal fungi (AMF) can colonize roots of an individual plant species but factors which determine the selection of a particular AMF species in a plant root are largely unknown. The present work analysed the effects of drought, flooding and optimal soil moisture (15–20 %) on AMF community composition and structure in Sorghum vulgare roots, using PCR-RFLP. Rhizophagus irregularis (isolate BEG 21), and rhizosphere soil (mixed inoculum) of Heteropogon contortus, a perennial C 4 grass, collected from the semi-arid Delhi ridge, were used as AMF inocula. Soil moisture functioned as an abiotic filter and affected AMF community assembly inside plant roots by regulating AMF colonization and phylotype diversity. Roots of plants in flooded soils had lowest AMF diversity whilst root AMF diversity was highest under the soil moisture regime of 15–20 %. Although plant biomass was not affected, root P uptake was significantly influenced by soil moisture. Plants colonized with R. irregularis or mixed AMF inoculum showed higher root P uptake than non-mycorrhizal plants in drought and control treatments. No differences in root P levels were found in the flooded treatment between plants colonized with R. irregularis and non-mycorrhizal plants, whilst under the same treatment, root P uptake was lower in plants colo- nized with mixed AMF inoculum than in non-mycorrhizal plants. Keywords Arbuscularmycorrhizalfungi . Fungalcommunity composition . Plant P uptake . Soil moisture . Root AMF diversity Introduction Soil microorganisms are important drivers of plant diversity and productivity in terrestrial ecosystems (van der Heijden et al. 2008) due to their central role in processes such as nutrient cycling, organic carbon sequestration and decompo- sition of soil organic matter (Herold et al. 2014). A key paradigm in ecology is the identification of factors that deter- mine species distributions and assemblages of biological com- munities (Cavender-Bares et al. 2009; Stegen et al. 2012; Freitas et al. 2013). Spatial distribution of soil microbial communities is tailored by deterministic and stochastic pro- cesses (Stegen et al. 2012). Deterministic processes accentuate differences in species responses to abiotic and biotic factors (Götzenberger et al. 2012; HilleRisLambers et al. 2012; Freitas et al. 2013). Arbuscular mycorrhizal fungi (AMF) may determine di- versity and coexistence of plant species (van der Heijden et al. 1998) through selective advantages they provide to host plants in facilitating uptake of nutrients, particularly phosphorus (P), from patchy sources and enabling tolerance to biotic and abiotic stresses (Augé 2001; Kiers et al. 2011; Smith et al. 2011). Ecological benefits derived by the plant from AMF may be offset by up to 20 % plant carbon (C) loss to the fungal symbiont (Jakobsen and Rosendahl 1990). Indeed, when soil P levels are high, AMF may not provide additional benefits to the host and even become parasitic through their C demand on the host (Olsson et al. 2010). The abundance and composition of AMF communities in roots and soils can be influenced by deterministic factors in the rhizosphere such as soil texture, temperature, pH, nutrient availability, organic carbon and soil Electronic supplementary material The online version of this article (doi:10.1007/s00572-014-0596-1) contains supplementary material, which is available to authorized users. S. Deepika : D. Kothamasi Laboratory of Soil Biology and Microbial Ecology, Department of Environmental Studies, University of Delhi, 110007 Delhi, India D. Kothamasi (*) Biosphere Impact Studies Unit, Belgian Nuclear Research Center (SCK•CEN), Boeretang 200, 2400 Mol, Belgium e-mail: dmkothamasi@cemde.du.ac.in Mycorrhiza (2015) 25:67–75 DOI 10.1007/s00572-014-0596-1