Fungal endorhizal associates of Equisetum species from Western and Arctic Canada

We describe endorhizal fungi associated with Equisetum species collected from Ellesmere Island (82A degrees N), Axel Heiberg Island (80A degrees N), and from sites in Yukon Territory and the Prairie Provinces (51-67A degrees N). Fungal colonization was assessed using a multiple quantitation microintersect method for lactofuchsin-stained roots examined with wide-field and confocal epifluorescence microscopy. Equisetum roots host abundant and diverse endorhizal fungal associates. For 85 specimens from 14 sites, total colonization averaged 30 A +/- 3%, range 0-97%. Colonization rates for wide aseptate hyphae characteristic of arbuscular mycorrhizae (5 A +/- 1%) was significantly less than for fine endophytes (20 A +/- 3%) or septate endophytes (17 A +/- 2%). Equisetum spp. are abundant in tundra and an important understory plant in boreal forests, where they are particularly common on burned or disturbed sites. Endorhizal fungi associated with Equisetum may have broad ecological relevance.