Objective  An endophytic fungus from its symbiotic Dendrobium officinale plant was identified and studied for its effect on the morphology of the host.

  Method  The fungus was isolated from the disinfected roots of a wild D. officinale plant grown on top of Mt. Guanzhai in Liancheng county. It was further purified on a PDA medium and labeled as T11 to be identified by morphological and 5.8 SrDNA-ITS molecular biological methods. After a 7 d-culture in a shaking flask, the inoculated liquid was added to the aseptically potted seedlings of D. officinale. Growth of the seedlings was observed for 6 months.

  Result  The milky white T11 colonies on the PDA plate had concentric rings on them. The T11 mycelial cells were binucleate, septate, and elliptical in shape. It was preliminarily identified as an Epulorhiza sp., an asexual plastic film fungus of Tulasnella calospora. Subsequently, the 5.8SrDNA-ITS sequence amplified from the DNA extracted from T11 as template showed the PCR fragment to be 630bp in length. The sequence alignment and phylogenetic tree clustered T11 in the same branch as the T. calospora of Cymbidium, with a 99% genetic homology. With the T11 inoculation, the D. officinale seedlings grew well with significantly increased plant height, leaf count, and leaf width.

  Conclusion  The morphological and molecular biological characteristics of T11 indicated it to be an Epulorhiza sp., the Basidiomycetes of orchidaceae mycorrhizal fungi, which is known to enhance the growth of D. officinale.