Re-introduction Technology Based On Mycorrhizal Fungi In The Conservation Of An Endangered Orchid: Dendrobium Loddigesii

As an important plant resource, native species of Dendrobium have huge development and economical value. However, wild orchid resources were decreasing and suffering serious destruction because of the official and ornamemental demand. Reconstruct nature original population is getting more essential, the conservation of Orchidaceae is getting more and more attentions. Re-introduction aims to improve ecosystem diversity and community stability, to rebuilt sustainable populations, and consequently to become an effective method in conservation of endangered and rare species, as well as the early-developed conservation methods including in-situ and ex-situ conservation methods. Re-introduction has been developed internationally for a relatively short time with little highly successful case, which could mainly attributed to inappropriate environmental factors in the reintroducing sites and lack of knowledge about the biology and ecology of the target species. In present paper, we pointed out that the re-introduction of endangered and rare orchids is particularly difficult since they often having a deep symbiosis relationship with other organisms such as fungi and host plants.Dendrobium loddigesii, one species of medicinal, was studied in this paper. In order to explore the function of Orchidaceae mycorrhizal fungi, improve the survival and growth rate of orchid plants, fungal strains were isolated from natural roots of D. loddigesii, and beneficial strains were screened by inoculated into D. loddigesii. Then, biological characteristics of the beneficial fungus were analyzed, cultivation of mycorrhization plant was studied, and the main facts of effect on the survival rate and adaptability of D. loddigesii seedlings reintroduction were preliminary studied. Which can be used as a guide to the species conservation in a larger scale, not only for the orchid but also other species. The main results are summarized as the following.(1) Isolation rate of D. loddigesii vary from sampling sites.Highest and lowest isolation rate of D. loddigesii were 91.00% and 10.42% respectively. Sampling in high altitude areas got higher isolation rate. And the isolation rate was different by growth substrate, Limestone>Granite>Basalt. seventy-two fungus were got after grouping, and eleven beneficial fungus were screened by re-inoculation with D. loddigesii seedlings. At last, Eleven beneficial fungus were identified by molecular characterization, including one of Epulorhiza sp.,one of Lecythophora sp.,one of Acremonium sp. and two of Tulasnella sp. others were indeterminated, and more of them were Ascomycota and Basidiomycota.(2) Beneficial fungus of D. loddigesii always has stronger phosphate-dissolving and cellulolytic capacity.Seven of ten beneficial fungus had hydrolysis, and three strong phosphate-dissolving fungi were screened. In which, the phosphate-dissolving of NO. F13 appeared earliest, NO. B14 appeared strongest, and the value of HD/CD was 1.58, NO. F24a was the second. Five of ten beneficial fungus had cellulolytic capacity, and the value of D/d of NO. F25 was 3.88. Co-culture of fungi and seedlings, we found three best fungus of NO. F9,F24a and F25 had stronger phosphate-dissolving and cellulolytic capacity.(3) The growth of biomass of D. loddigesii is varying from the different fungus, different symbiotic time and different seedling stage.Compared with seedlings asymbiotic with fungi, seedlings symbiotic cultrued with fungi had growth advantages except NO. F12. In which, NO. F24b,B14,F25 were good for protocorms of D. loddigesii sown seeding; And in plantlet-promoting stage, the biomass weight increase rate of D. loddigesii seedlings symbiotic cultured with endophytic fungi for ten weeks increased much more contrast to asymbiotic culture. But co-culture for seven weeks appeared best contrast to asymbiotic culture in rooting stage, and in the sixteen weeks, the biomass weight increase rate of seedlings symbiotic cultured with NO. B14,F34 and F13 increased significantly. Finally, we got the better endophytic fungi of NO. B14,F24b,F13 and F25. Both Survival rate and seedling growth present well cultured with fungi of NO. F24a and B14. during growing period, and NO. F12,F34,F13 and B14 had higher re-isolation rate.(4) Habitats and seedling stage are the main facts that having influences on the survival rate of reintroduction of D. loddigesii.In the three habitats, we found that the NO. two where was the history habitats of D. loddigesii had better survival rate, and NO. three where was the similar habitats of D. loddigesii also had good survival rate. However, the habitats in existence of NO. one had lower survival rate, showed that the survival rate had little connect with the number of the species in existence. With the improving of seedling size, the survival rate improved in the same habitat. And whether inoculating fungi or not had little influences on the reintroduction of D. loddigesii during three months, but NO. F24a and F9 appeared good. NO. F24a and F12 were good for seedling growth potential of D. loddigesii seedlings reintroduction after seven months. There weren't obvious differences in survival rate between planting in tree and in stone, except more leaves fallen from group that grew in tree.