| Cymbidium forrestii has high ornamental, economic, and cultural values as a traditional flower. Due to over exploitation and low rate of seed germination in natural state, resources is gradually becoming exhausted. Protecting of Cymbidium species resources becomes the focus of our study. In order to provide theory for solving the low multiplication ratio of tissue culture and low survival rate of plantlets, The tissue culture system of Cymbidium forrestii and symbiotic fungi were studied. The major achievements are as follows:(1) The effect of different carbon sources, different organic compounds, different concentration of NAA on multiplication of Cymbidium forrestii'Songmae'rhizome: Sucrose was the optimal carbon source added in the basic culture medium, the multiplication ratio arrived to6.8, which was separately1.31 times, 1.24 times, 1.79 times of Sugar, Fructose, Glucose. The multiplication ratio of coconut water, apple juice, banana juice in the basic culture medium was separately 6.7,5.3,4.8, so the effect of coconut water on multiplication of Cymbidium forrestii was better than banana juice and apple juice, what's more, addition of 10% coconut water had advantages in length of new rhizome, fresh weight and dry weight compared with 5%; adding the plant growth regulators combination of 0.1mg/LBA+3～5mg/LNAA in the basic culture medium was better to the multiplication of rhizome, higher or lower concentration of NAA may inhibit it.(2) The effect of plant growth regulators on differentiation of Cymbidium forrestii'Songmae'rhizome:BA and NAA take part in physiological and biochemical of Cymbidium forrestii, adding the plant growth regulators combination of 0.1mg/LBA+3～5mg/LNAA in the basic culture medium was suitable for the differentiation of rhizome, and the differentiation ratio of buds was 94%.(3)The effect of combination of different concentration of BA and IBA, activated charcoal on rooting and strong sprouts of Cymbidium forrestii'Songmae': The treatment of 0.1mg/L BA +0.5mg/L IBA was superior to other treatments, which average height of plantlets, number of roots and average rate of rooting was respectively 4.05cm, 4 and 87.9%. Appropriate concentration of activated carbon was good to the growth of Cymbidium forrestii plantlet, especially roots, the optimum concentration was 2g/L.(4) The effect of different temperature, humidity, light intensity and symbiotic bacteria'Oh-Chid'on acclimation of Cymbidium forrestii plantlets: Suitable temperature for the growth of orchids was about 20℃, the survival rate of plantlets is 95% in the environment of 20℃, while 60% in the environment of 25℃; Generally speaking, orchid grow well under the humidity of 70% in the stage of growing, However the treatments of 80% was a little better to maintain plantlets not wilt in the early acclimation. Plantlets grown thin and slowly obviously under the light intensity of 40μmol·m?2·s?1, and two plantlets dead in 20, but plantlets all arrived under the light intensity of 80μmol·m?2·s?1, which were healthy, strong and with more new leaves. Symbiotic bacteria provide essential nutrient for the growth of orchid. Number of new roots and root length in basic culture medium of adding symbiotic bacteria'Oh-Chid'was separately 1.57 times, 1.79 times compared with CK, and plantlets in basic culture medium of adding symbiotic bacteria'Oh-Chid'grown faster, healther and had lower mortality rate. .(5)Separatiation,purification and identify of mycorrhizal Fungi of orchid: According to the analysis of the strains and matching of DNA sequence, there were 17 strains collected from four orchids, fourteen strains separately belong to Mortierella(10), Mucoromycote (3)and Trichoderma(1), when they symbiosis with Dendrobium candidum plantlets in flask, it showed that FC8,FC11 promoted the growth of Dendrobium candidum plantlets obviously.
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