Cultural Endophytic Fungi Associated with Dendrobium Officinale :Identification, Diversity Estimation and their Antimicrobial Potential

Endophytic fungi associated with Chinese medicinal plant Dendrobium officinale have been revealed using the culture-dependent approach and the diversity and antimicrobial activity have been examined in this study. A total of 105 endophytic isolates representing 16 fungal morphotypes were recovered from the ischolar_mains, stems and leaves of D. officinale. Identification by ITS-rDNA sequencing showed 12 distinct operational taxonomic units, and most of them were classified into species level. Shannon's and Simpson's indices were calculated to quantify fungal diversity. The results demonstrated that endophytic fungi associated with D. officinale were moderately diverse, and fungal species among three tissues was also different which exhibited tissue-specificity. The composition of endophyte assemblages from the ischolar_mains was most abundant and diverse, followed by the stems, while the leaves possessed relatively low isolation rate. Fusarium oxysporum (21.0%) and Xylaria cubensis (20.0%) were the most dominant species, while Colletotrichum sp. and Pestalotiopsis sp. were also frequently isolated. Three species (F. oxysporum, Aspergillus niger and Aureobasidium pullulan) showed broad-spectrum antimicrobial activity, and F. oxysporum had acute inhibition to pathogens tested. Our systematic study could enrich the current knowledge on diversity of endophytic fungi. The fungal isolates from D. officinale may be used for exploration of novel bioactive compounds and have potential as biocontrol agents.