Arbuscular mycorrhizal and dark septate endophyte fungal associations in South Indian grasses Kullaiyan Sathiyadash & Thangavelu Muthukumar & Eswaranpillai Uma Received: 3 September 2010 / Accepted: 10 October 2010 / Published online: 21 October 2010 # Springer Science+Business Media B.V. 2010 Abstracts We examined arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungal association in 50 south Indian grasses from four different sites. AM fungal diversity was also compared among the different sites. Forty-four of the 50 grasses examined had AM association and dual association with DSE fungi occurred in 25 grasses. We report for the first time AM and DSE fungal status in 23 and 27 grasses respectively. Arum-type AM morphology was the dominant occurring in 21 grasses with typical Paris-type colonization occurring in 6 grasses. AM morphology is reported for the first time in 35 grasses. Over the different sites, spore density in the soil ranged from 5–22 per 100 g air-dried soil. Spores of 11 AM fungal taxa were isolated from the soil samples of grasses of which nine belonged to Glomus, one to Acaulospora and one to Scutellospora. No significant relationship existed between AM fungal colonization and spore numbers. Species richness was high in site II and Glomus aggregatum, Glomus viscosum and Glomus mosseae were most frequent species at different sites. Overall species diversity indices (Simpson index, Shannon-Weaver index, species equitability index) differed significantly between sites. Keywords Arum-type . DSE fungi . Grasses . Mycorrhiza . Paris-type . Spores 1 Introduction The family Poaceae with approximately 10,000 species in six sub-families and forty tribes is one of the largest plant families (Mabberley 1997). Members of this family commonly known as grasses are cosmopolitan in distribu- tion occurring in a wide range of edaphic and climatic conditions. In addition, grasses satisfy around 80% of our nutrient requirements and includes some of the worlds important crop plants (Stebbins 1972). Arbuscular mycorrhizal (AM) fungi are integral compo- nents of most terrestrial ecosystems. These fungi influence terrestrial plant communities both indirectly through their interactions with soil or directly through their interaction with the host plant. The fungus obtain carbon from the host plant and in return assist the plants in their uptake of phosphorus (P), nitrogen (N) and other mineral nutrients from deficient sites (Smith and Read 2008). The non- nutritional benefits of AM association include improved water relation, increased resistance to root pathogens, mineral element toxicity and stable soil structure (Turk et al. 2006). It has been predicted that taxa belonging to more than 80% of the plant families are mycorrhizal. Inspite of its large family size, less than 500 species of grasses have been examined for their mycorrhizal status (Ragupathy and Mahadevan 1993; Muthukumar and Udaiyan 2000; Wang and Qiu 2006; Chaudhry et al. 2005, 2006, 2009; Fracchia et al. 2009). Based on the occurrence of AM fungal structures within plant roots, AM morphology has been classified as Arum-, Paris- or intermediate-types. The Arum-type mycorrhizal colonization consists of intercellular hyphae, vesicles and intracellular arbuscules. The Paris-type is characterized by intracellular hyphal coils or arbusculate coils with or without vesicles. Intermediate-type shows the characteristics of both K. Sathiyadash (*) : T. Muthukumar : E. Uma Root and Soil Biology Laboratory, Department of Botany, Bharathiar University, Coimbatore 641 046 Tamil Nadu, India e-mail: ksd.bio@gmail.com Symbiosis (2010) 52:21–32 DOI 10.1007/s13199-010-0096-9