Endophytic Fungus From The Dendrobium Plants And Effects On Seed Germination And Seeding Growth

Dendrobium plant is the second-largest genera, only behind Cymbidium plant, among the Orchidaceae, one of the world's largest plant families. With the market demand of Dendrobium plant ever-increasing, the quantity of wild Dendrobium plant dropped drastically because of the temptation of market huge profits. All orchids have an obligate relationship with mycorrhizal symbionts during seed germination and plant growth under field conditions. Therefore, Investigation the diversity of endophytic fungus from Dendrobium plants, it is vital significance not only in practicality on enlarging our country's orchid industry but also in the conservation of orchid plants. In this study, we chose eight species of Dendrobium plants from four different habitats that are Hunan, Guangxi, Anhui, Guizhou as our research samples, they are D.officinale, D.lohohense, D.hercoglossum, D.huoshanense, D.moniliforme, D.hancockil, D.loddigesii and D.chrysanthum. The fresh nutrition roots of the eight Dendrobium plants were sampled in growth stage both 2009 and 2010 year. The detail includes to isolate and identify fungi from the fresh nutrition roots; to analysis the phylogenetic diversity of the endophytic fungus; to investigate the symbiotic germination in vitro between D.huoshanense seeds and endophytic fungus and to investigate the symbiotic effect between endophytic fungus and the protocorm and seedlings of D.moniliforme in flask. The main results were as follows:1. we using tissue blocks cultivation method to isolate the endophytic fungus from the fresh nutrition roots, using two methods there are microstructure examination and ITS gene sequence analysis to identify, we got 87 fungi strains from the samples. The result of ITS gene sequence analysis indicated that the fungus of isolated included Ascomycota and Basidiomycota. The Ascomycota was predominant. The fungus of Ascomycota belonged to Hypocreales and Xylariales, the fungus of Basidiomycota belonged to Tulasnellaceae among them. Species number of endophytic fungus from the Dendrobium plants indicates that diversity of endophytic fungus from the same Dendrobium plants under different habitats and the different Dendrobium plants under same habitat are abundance and difference to some extent.2.20 endophytic fungus which were chose from the 87 fungus strains were use in symbiotic germination in vitro with the seeds of D.huoshanense. The viability of seeds of D.huoshanense is 37% according to TTC staining examination. After 12 weeks, there are 6 endophytic fungus can promote the embryo germinated. The results showed that the relationship between seed germination rate and the viability of seeds is not direct ratio.3. There are two purposes on study the protocorm and seedlings of D.moniliforme were inoculated with different fungus strains in flask. One is to choose the optimal medium from three different symbiotic medium; the another is to further exploration the symbiotic effect between endophytic fungus and the Dendrobium plants. After 12 weeks, we can see that oat medium is the optimal medium. There are 2 strains can promote protocorm differentiated into leaves or roots obviously in symbiotic germination. There are 9 fungus strains can make the fresh mass of seedlings of D.moniliforme higher than the control in the seedling-fungi symbiotic cultivation. could The results suggest that mycorrhizal symbionts has been successfully created through dyed the mycorrhiza of the seedling-fungi symbiotic cultivation.