High specificity generally characterizes mycorrhizal association in rare lady's slipper orchids, genus Cypripedium

Abstract

Lady's slipper orchids (Cypripedium spp.) are rare terrestrial plants that grow throughout the temperate Northern Hemisphere. Like all orchids, they require mycorrhizal fungi for germination and seedling nutrition. The nutritional relationships of adult Cypripedium mycorrhizae are unclear; however, Cypripedium distribution may be limited by mycorrhizal specificity, whether this specificity occurs only during the seedling stage or carries on into adulthood. We attempted to identify the primary mycorrhizal symbionts for 100 Cypripedium plants, and successfully did so with two Cypripedium calceolus, 10 Cypripedium californicum, six Cypripedium candidum, 16 Cypripedium fasciculatum, two Cypripedium guttatum, 12 Cypripedium montanum, and 11 Cypripedium parviflorum plants from a total of 44 populations in Europe and North America, yielding fungal nuclear large subunit and mitochondrial large subunit sequence and RFLP (restriction fragment length polymorphism) data for 59 plants. Because orchid mycorrhizal fungi are typically observed without fruiting structures, we assessed fungal identity through direct PCR (polymerase chain reaction) amplification of fungal genes from mycorrhizally colonized root tissue. Phylogenetic analysis revealed that the great majority of Cypripedium mycorrhizal fungi are members of narrow clades within the fungal family Tulasnellaceae. Rarely occurring root endophytes include members of the Sebacinaceae, Ceratobasidiaceae, and the ascomycetous genus, Phialophora. C. californicum was the only orchid species with apparently low specificity, as it associated with tulasnelloid, ceratobasidioid, and sebacinoid fungi in roughly equal proportion. Our results add support to the growing literature showing that high specificity is not limited to nonphotosynthetic plants, but also occurs in photosynthetic ones.

Analysis of fungal diversity in Orchis tridentata Scopoli

“…As ceratobasidioid fungi have been found as symbionts or putatively symbionts of several orchid species, such as C. damasonium [10], C. longifolia [28], Cypripedium spp. [39], Dactylorhiza majalis (Reichenbach) P.F. Hunt et Summerhayes, E. gigantea, E. helleborine (L.) Crantz, E. palustris (L.) Crantz and Platanthera chlorantha (Cust.)…”

Enigmatic Sebacinales

“…Sebacinoid ORMs were detected in Epipactis palustris in a wetland site not accompanied by ectomycorrhizal plants in Northeast Bavaria, Germany (Bidartondo et al 2004). Shefferson et al (2005) found that high specificity generally characterizes ORMs in Cypripedium species from North America and Estonia. Mycoendophytes of terrestrial Acianthus, Caladenia and Pterostylis of Southeast Queensland appeared to be specific for their hosts (Bougoure et al 2005).…”

Interactions of fungi with other organisms

“…Molecular studies have shown that most fungi involved in most fungi involved in ORM are basidiomycetes (Taylor et al 2002;Shefferson et al 2005;Girlanda et al 2006Girlanda et al , 2011Suárez et al 2006;Pecoraro et al 2012b; Dearnaley Fungal interactions 3 et al 2012), but some orchid species form symbioses with ascomycetes (Bidartondo et al 2004;Selosse et al 2004;Shefferson et al 2008).…”