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Keywords:

  • ITS identification;
  • morphology;
  • multivariate statistics;
  • phylogeny;
  • reintroduction;
  • symbiotic germination

ABSTRACT

In nature, orchids are fully dependent on mycorrhizal fungi to germinate their seeds. These fungi can penetrate root cells and form pelotons, hyphal coils responsible for providing simple sugars for the orchid embryo. During the achlorophyllous seedling stage, orchids depend on fungi; and some species remain dependent through life, while others establish photosynthesis but, to varying degrees, remain facultatively dependent or responsive to fungal colonization as adults. The aim of this study was to identify how many clades of fungi can establish mycorrhizal associations with Coppensia doniana, a widespread orchid in Campos do Jordão (Brazil) and to demonstrate how morphological features can be useful to group and identify these fungi. Plants were collected during the dry season of 2009 near Campos do Jordão State Park. Fungi were isolated by transferring root segments containing pelotons to media. Three main clades of fungi were formed by either qualitative or quantitative morphological data. We identified these fungi as two morphotypes of Ceratorhiza (anamorphic stage of Ceratobasidium) and one uninucleate Rhizoctonia. The internal transcribed spacer (ITS) sequencing data corroborated the morphological features showing the same three clades; all isolates showed a high similarity with Ceratobasidium ITS sequences in GenBank. Thus, it was possible to demonstrate a high affinity between this orchid species of Oncidiinae and Ceratobasidium. Morphological data associated with multivariate statistics proved to be a useful tool in multilevel taxonomy of these orchid-associated fungi.

Abstract in Portuguese is available in the online version of this article.