Mycorrhiza (2004) 14:139–142 DOI 10.1007/s00572-004-0298-1 SHORT NOTE Analía I. Sannazzaro · Oscar A. Ruiz · Edgardo Albertó · Ana B. MenØndez Presence of different arbuscular mycorrhizal infection patterns in roots of Lotus glaber plants growing in the Salado River basin Received: 7 October 2003 / Accepted: 3 February 2004 / Published online: 27 February 2004  Springer-Verlag 2004 Abstract Morphological types of arbuscular mycorrhizal (AM) fungi associated with Lotus glaber in sodic soils of the Salado River basin were studied. At least eight colonization patterns (IP) of AM fungi in roots of L. glaber were observed after 30 plants were analyzed. Arum- and Paris-type infection were found in the same plant species. This result supports the idea that AM morphology is not solely under plant control, but is also influenced by fungal identity. One infection pattern, presumably corresponding to Glomus intraradices, and a second, possibly assignable to Glomus tenue, were the most commonly found. Our results reinforce previous suggestions that G. intraradices is well adapted to sodic- saline conditions and may play a role in the resistance of L. glaber to these soils. Keywords Arbuscular mycorrhizae · Lotus · Infection pattern · Arum · Paris Introduction Lotus glaber is a warm-season, perennial legume from Europe that became naturalized in the flooding pampas of Argentina only a few decades ago. It is the best-adapted species used as forage for cattle production in the Salado River basin (910 6 ha). Soils in this region are limed, poorly drained and present a severe phosphorus deficien- cy (2–10 ppm), medium organic matter levels, high alkalinity and salinity, together with periodic exposure to waterlogged conditions, which significantly decrease persistence and yield of common legumes (Mazzanti et al. 1986). Most vascular plant taxa have symbiotic associations with arbuscular mycorrhizal (AM) fungi, and soils bear- ing native or cultivated host plants harbor these fungi (Mosse 1973; Harley and Smith 1983). AM fungi have been shown to improve phosphorus nutrition and plant tolerance to abiotic stresses (Ruiz-Lozano et al. 1996; Ruiz-Lozano and Azcon 2000). The taxonomy of AM fungi is based mainly on morphological characteristics of their spores. However, since the number of available taxonomic characters is limited and identification of species that colonize roots in the field is usually difficult, other attempts to classify AM fungi in roots have been made on the basis of their intraradical mycelial morphol- ogy (Abbott 1982; Morton 1988; Brundrett et al. 1996; Merryweather and Fitter 1998). Two morphological types of AM fungi in roots have been described, namely Arum- and Paris-type (Gallaud 1905; Smith and Smith 1997). The Arum-type of coloni- zation is defined by hyphae growing intercellularly in the root cortex and penetrating the cortical cells to produce arbuscules as terminal structures on “trunk hyphae”. The Paris-type is defined by the absence of intercellular hyphae and the presence of extensive coils of intracellular hyphae within cortical cells, from which arbuscules are formed as intercalary structures and intracellular vesicles. It was first suggested that AM morphological type is largely dependent on the plant species, and that this could be related to the presence or absence of extensive air- spaces in roots (Brundrett and Kendrick 1988). However, Smith and Smith (1997) considered the potential role of the fungal genome in the determination of the morpho- logical type of AM, and some studies have demonstrated differences in morphology of AM in a single plant species when colonized with different fungal species (Abbott 1982; Cavagnaro et al. 2001). A. I. Sannazzaro · O. A. Ruiz · E. Albertó · A. B. MenØndez Unidad Biotecnológica 1, Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomffls (IIB-INTECH), 7130 Chascomffls, Pcia de Buenos Aires, Argentina A. B. MenØndez ( ) ) Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Piso 4, Pab II, Ciudad Universitaria, 1428 Buenos Aires, Argentina e-mail: anamen@bg.fcen.uba.ar Tel.: +54-11-45427396 Fax: +54-11-47872706