Abstract Root and soil samples of three potted or ground-grown cycads (Cycas circinalis, C. revoluta, Zamia sp.) were collected between November 1999 and June 2000 and surveyed for arbuscular mycorrhizal (AM) colonization and spore populations. AM fungi were associated with all root systems and rhizosphere samples examined. Root colonization was of a typical Arum type and AM colonization levels differed signifi- cantly between species and between potted and ground- grown cycads. Mycorrhizal colonization levels were inversely related to root hair number and length. Spores of nine morphotypes belonging to three genera (Acau- lospora, Glomus, Scutellospora) were extracted from soil. The percentage root length colonized by AM fungi was not related to soil factors, but total AM fungal spore numbers in the rhizosphere soil were inversely related to soil nitrogen and phosphorus levels. AM fungal spore numbers in the soil were linearly related to root length colonized. The co-occurrence of septate non-mycorrhizal fungi was recorded for the first time in cycads. These observations and the relationship between plant mycor- rhizal status and soil nutrients are discussed. Keywords Cycads · Arbuscular mycorrhizas · Arum type · Arbuscule · Glomus Introduction Arbuscular mycorrhizal (AM) fungi are believed to have facilitated colonization of terrestrial environments by vascular plants in Siluro-Devonian times and mycotro- phy is considered to be an ancestral condition (Cairney 2000). The cycads, a group of primitive slow-growing, woody plants which appeared in the upper Triassic, are restricted entirely to tropical and subtropical regions (Jones 1993). Cycads are unique in possessing cyanobac- teria as nitrogen (N)-fixing symbionts in their corolloid roots (Zimmerman and Rosen 1992). Although AM as- sociation in N-fixing legumes and actinorrhizal trees is well documented, little is known about the mycorrhizal association in plants with cyanobacteria as N-fixing symbionts. Ecto- and endomycorrhizal associations have been re- ported widely in several gymnosperms (see Smith and Smith 1997), but little information is available on the my- corrhizal status of cycads (Brundrett and Abbott 1991; Lamnot 1982). The IUCN has classified more than half of the 182 species of the order Cycadales (Stevenson and Osborne 1993) as endangered, vulnerable or rare (Gilbert 1984). Four cycad species, Cycas circinalis L., C. pecti- nata Griff., C. rumphii Miq. and C. beddomei Dyer occur naturally in India (Pant 1973). Of these, only C. circinalis occurs in southern India. In addition, C. revoluta Thunb., a native of Japan, and a species of Zamia, native to tropi- cal and temperate regions of Africa, Australia and Ameri- ca, are introduced and are widely cultivated in gardens (Henry et al. 1989). In view of the paucity of information on the mycorrhizal status of cycads, the present investiga- tion was carried out on three cycads occurring in southern India to elucidate the role of root morphology and eda- phic factors on their mycorrhizal status. Materials and methods Eighteen root and soil samples were collected from three potted or ground-grown cycad species (Cycas circinalis, C. revoluta, Zamia sp.) from November 1999 through June 2000; one sample con- tained C. circinalis occurring naturally in Nilgiris of Western Ghats, southern India. To assess mycorrhizal colonization and AM fungal spores, 3-cm-diameter × 10-cm-deep (100 g) soil samples were taken at three random points between the stem and pot pe- riphery in potted cycads. Similarly, for ground-grown cycads, the samples were collected at three random points 15 cm away from the stem around each cycad. Root material for each sample was removed manually from the soil and washed in water to remove debris. Since root morphology is known to influence the mycorrhizal status, the length and num- ber of root hairs per mm of root were determined. Samples of 10 T. Muthukumar ( ✉ ) · K. Udaiyan Microbiology Laboratory, Department of Botany, Bharathiar University, Coimbatore-641 046, Tamil Nadu, India e-mail: tmkum@yahoo.com Fax: +91-422-422387 Mycorrhiza (2002) 12:213–217 DOI 10.1007/s00572-002-0179-4 SHORT NOTE T. Muthukumar · K. Udaiyan Arbuscular mycorrhizas in cycads of southern India Received: 21 May 2001 / Accepted: 23 April 2002 / Published online: 15 June 2002 © Springer-Verlag 2002