title: Characterization of mycorrhizal fungi isolated from the threatened Cypripedium macranthos in a northern island of Japan: two phylogenetically distinct fungi associated with the orchid.
abstract: We isolated Rhizoctonia-like fungi from populations of the threatened orchid Cypripedium macranthos. In ultrastructural observations of the septa, the isolates had a flattened imperforate parenthesome consisting of two electron-dense membranes bordered by an internal electron-lucent zone, identical to the septal ultrastructure of Rhizoctonia repens (teleomorph Tulasnella), a mycorrhizal fungus of many orchid species. However, hyphae of the isolates did not fuse with those of known tester strains of R. repens and grew less than half as fast as those of R. repens. In phylogenetic analyses, sequences for rDNA and internal transcribed spacer (ITS) regions of the isolates were distinct from those of the taxonomically identified species of Tulasnella. On the basis of the ITS sequences, the isolates clustered into two groups that corresponded exactly with the clades demonstrated for other Cypripedium spp. from Eurasia and North America despite the geographical separation, suggesting high specificity in the Cypripedium-fungus association. In addition, the two phylogenetic groups corresponded to two different plant clones at different developmental stages. The fungi from one clone constituted one group and did not belong to the other fungal group isolated from the other clone. The possibility of switching to a new mycorrhizal partner during the orchid's lifetime is discussed.
authors.affiliation: Laboratory of Crop Physiology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Kita 9, Nishi 9, Sapporo, 060-8589, Japan. hana@res.agr.hokudai.ac.jp.
authors.forename: Hanako
authors.initials: H
authors.lastname: Shimura
authors.affiliation: Laboratory of Plant Pathology, Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Sadamoto
authors.affiliation: Laboratory of Crop Physiology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Kita 9, Nishi 9, Sapporo, 060-8589, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Matsuura
authors.affiliation: Forest Dynamics and Diversity Group, Hokkaido Research Center, Forestry and Forest Products Research Institute, Sapporo, 062-8516, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawahara
authors.affiliation: Laboratory of Plant Pathology, Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Naito
authors.affiliation: Laboratory of Crop Physiology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Kita 9, Nishi 9, Sapporo, 060-8589, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Koda
mesh_terms: D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005843:Geography; D025301:Hyphae / Q000254:growth & development; D007564:Japan; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D029595:Orchidaceae / Q000382:microbiology*; D010802:Phylogeny; D012232:Rhizoctonia / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer