Studies On Isolation, Identification And Bioactivity Of Endophytic Fungi From Dendrobium Candidum Grew In Huanjiang Of Guang Xi

Dendrobium candidum is the perennial, epiphytic herbs of Orchid Dendrobium, which is recorded Pharmacopoeia of the five kinds of Dendrobium, known as the best in the category of Dendrobium. The main active ingredients of Dendrobium candidum are Dendrobium polysaccharide, Dendrobium alkali, amino acids, of which the content of Dendrobium polysaccharide highly reaches 21.7%. Dendrobium candidum is one kind of traditional Chinese medicines, which has the functions for benefiting the stomach, promoting the production of body fluid, nourishing Yin and moistening the lungs. The paper studies on the species and biological activity of endophytic fungi from Dendrobium candidum on Huanjiang Country of Guangxi Mulun National Nature Reserve by tissue isolation, bacterium discs techniques. The results are as the follows:1. Firstly 37 strains were isolated from the roots of Dendrobium candidum with tissue method. Then the isolated endophytic fungi were observed under microscope. Combined with classic morphologic classification, Samardo and Hugues-Tubaki-Barron fungi classification system, 4 kinds of endophytic fungi with coindiophore were identified. They were subjected to Fusarium spp.,Cephalosporium sp. and Ovulariopsis sp.. The rest kinds (89.2%) were mycelium steriled under the experiments. 33 strains without coindiophore were identified by PCR method to recognize the sequence of the rDNA ITS1-5.8S-ITS4 regions (internal transcribed spacer ITS). In comparison with similar taxa, the sequence was grouped together with the known strains.2. Interaction between each fungi and seedling was studied by co-cultuvation 7 strains had significatly positive effects on the growth of seedlings of Dendrobium candidum in various growth parameters including fresh weight, dry weight, number of new roots, number of new leaves, as well as numbers of new buds. The 7 strains did not only promote the growth of Dendrobium candidu, but also enhance the content of polysaccharide of Dendrobium candidum on MS co-culture medium. Compared to the control group, the 7 strains cutured together with Dendrobium candidum could greatly affect the content of polysaccharide of the host, and the highest polysaccharide level reached 76.5%.3. The strain Escherichia coli, Staphylococcus aureus, Bacillus subtills, Candida albicams,Cryptococcus neoformans Vuillemin and Aspergillus fumigatus Fresenius, standing for G~+,G~- and fungus, respectively were selected as detecting strains to screen the antimicrobial activity of 37 strains isolated from Dendrobium candidum. The results show 18 strains of endophytic fungi showed the antimicrobial activity at least to one of the strains. The suspect can be supported the results that the endophytic fungi of Dendrobium candidum were the good pool of the antimicrobial activity strain.4,The strain AF-02 and AF-04 respectively were selected as detecting strains to screen the antimicrobial activity of 87 strains isolated from Dendrobium candidum. The results show 7 strains of endophytic fungi showed the antimicrobial activty at least to one of the strain. The suspect can be supported the results that the endophytic fungi of Dendrobium candidum were the good pool of the antimicrobial activity strain of the black spot disease of Dendrobium candidum.