Isolation and Identification of Endophytic Fungi from the Roots of two epiphytic orchids: Rhynchostylis retusa (L.) Bl. and Vanda tessellata (L.) Bl

Abstract

Two fungal endophytes were isolated and identified from two indigenous orchids of Bangladesh namely, Rhynchostylis retusa (L.) Bl. and Vanda tessellata (L.) Bl. Nature of fungal colonization, seasonal variations of colonization in root cortex cells were also studied. The fungal endophytes isolated from two different orchids differed in their cultural morphology and microscopic features such as colony morphology, colour of the colony, presence/absence of monilioid cells or spores and diameter of vegetative hyphae. The microscopic features i.e., hyphal structure, right-angle branching of hyphae, slight constriction at the branching point, shape and diameter of monilioid cells of the endophytic fungus isolated from R. retusa showed resemblance with the anamorphic Rhizoctonia-like fungi Ceratobasidium sp. On the other hand, the fungal endophytes isolated from the roots of V. tessellata produced huge number of spores. The cultural characteristics and spore morphology of this fungi corroborated resemblance with pathogenic fungi, Fusarium sp. The identity of the fungi was further reconfirmed through sequencing of the internal transcribed spacer (ITS) of the nuclear ribosomal DNA (nrDNA). The BLASTn search of ITS region sequences of the endophytic fungi isolated from R. retusa exhibited maximum similarity (97%) with an orchid mycorrhizal fungi (OMF), Ceratobasidium papillatum (GeneBank Accession No. OQ073691), while the fungal endophyte isolated from V. tessellata showed maximum similarity (99%) with Fusarium ambrosium (GeneBank Accession No. OP752102). The phylogenetic tree constructed using ITS region sequences of the isolated fungal endophytes and their closely linked species from genebank data developed two distinct groups. The conventional and molecular approaches applied for identification of these OMF can be followed for easy and accurate identification of other OMF.