| As an important plant resource,the Orchidaceae has high value in economy and scientific research.Many orchids require endomycorrhizal fungi for their survival and development,therefore, mycorrhization in tissue culture is a useful technique for the large quantity propagation of endangerous orchids.The purpose of this study was to find several orchid mycorrhizal fungi and optimize their growth in sterile culture.The details of this paper included isolation and preservation of mycorrhizal fungi of orchids, multiplication culture of protocorm;screening fungal elicitor and association which promoted growth of protocorm and differentiation of adventitious bud of Cymbidium eburneum;screening mycorrhizal fungi which promoted growth of tissue culture of Cymbidium insigne;observation of microstructure of mycorrhiza;identification of strains.The main results were as follows:1.The suitable medium of protocorm-like body of Cymbidium.Goeringii is KC +1.0mg/L NAA.The best for PLB of Cymbidium eburneum multiplication is 1/2MS medium,the young plants grew vigorously after differentiation and were more likely to live.2.Tissue cultures of C.eburneum were induced on culture medium with the fungal elicitor.In biomass increasing,the inducing effects were in the order of HF26＞CF6＞CF8.3.Tissue cultures of C.eburneum were induced on culture medium with the fungal elicitor.Compared to the control,the inducing effects of DMF80 and H+C did the best in biomass increasing,and the fresh weight of DMF80 getting extremely.HF26 strain had a remarkable effect on differentiation of leaves and aerial roots;DMF80 strain can promote basal roots number;fungal elicitor association had a remarkable effect on polysaccharide content.4.Tissue culture seedlings of the Cymbidium insigne were inoculated with seven fungal strains.After inoculated with strains CF2.CF8 and DMF80 for three months,the fresh weight of the seedlings increased significantly.And also the three fungal were obtained by re-isolating.Pelotons,regarded as typical structures of orchid mycorrhizae,were also found in the inoculating roots under a microscope.It seemed that the strains of CF2,CF8 and DMF80 associated with the Cymbidium insigne well.5.The observation of the mycorrhizal microstructure of Cymbidium insigne showed that it belonged to the typical mycorrhiza of orchids.The infection pathway started with the invasion of the fungi into the velamen and then entered the cortical tissue by breaking the velamen.The pelotons were irregularly distributed in the cortex,mainly in several of the outer cortical cells.In infected cortical cells,pelotons often occurred near the nucleus or twisted with them together which was the main existing way of pelotons.The hyphae penetrated through the wall of cortical cells and continuously spread inwards. Fresh pelotons and deformed pelotons in the cortical cells occurred simultaneously,and the hyphae provided nutrients to plants when they were digested and absorbed.6.After identification,these strains used for this study belong to Ceratorhiza,Aspergillus, Umbelopsis,Alternaria,Chaetomium,Fusarium and Epulorhiza. |
