Isolation, Identification And Functional Analyses Of Endophytes From Five Species Of Dendrobium In Pu’er, Yunnan

Dendrobium is the second largest genus in Orchidaceae and a perennial andherbaceous plant with higher medicinal and ornamental value. However, the wildDendrobium resources are decreasing because of over collection and habitat destruction. Inrecent years, Dendrobium-growing area has been increasing in Yunnan province. Butdiseases, pests and nutritional deficiencies are also more and more severe. In this thesis,endophytic bacteria and fungi were isolated from5species of Dendrobium in Pu’er ofYunnan and identified based on their16S rDNA and ITS sequences, respectively, andanalysed by the laboratory and field experiments for their partial functions. The goal of thisstudy is to find out the diversity of endophytes and screen some beneficial strains. Themain research results are as following:1. The number of endophytes varies in5species and3tissues of Dendrobium. Total130bacterial strains were isolated, among them48from D. chrysotoxum and34from D.aurantiacum, and in order of numuber D. chrysotoxum showed leaf> stem> root, D.thyrsiflorum showed stem> leaf> root, D. aurantiacum, D. nobile and D. chrysanthumshowed root> stem> leaf. Total361fungal strains were isolated, among them91werefrom D. chrysanthum and85from D. nobile, and the strains in leaf of5species are morethan stem and root.2. The endophytic bacteria were identified as8genera based on their16S rDNAsequence, among which Bacillus is dominant and other common genera are Acinetobacter,Enterobacter and Klebsiella. The fungi were identified as27genera based on their ITS sequence, Colletotrichum and Fusarium are dominant. The highest shannon diversityindex(H’) of endophytic fungi is2.21from D. chrysotoxum, and that of leaf’s is0.95-1.39higher than stem’s0.47-1.01and root’s0.41-0.82in5Dendrobium. The similaritycoefficient(Cs) between2Dendrobium species is0.27-0.75with the highest value0.75between D. thyrsiflorum and D. aurantiacum.3. Total33antagonistic bacteria were screened. They belonged to Bacillus,Acinetobacter and Streptomyces, and could inhibit at least one pathogen among Fusariumoxysporum, Fusarium solani, Phytophthora parasitica var. nicotianae and Enterobactercloacae. Total8antagonistic fungi were screened and identified as Guignardia, Fusariumand Xylariaceae, they could inhibit at least one beteween Fusarium oxysporum andPhytophthora parasitica var. nicotianae.4. Seven growth-promoting bacterial strains were screened. In pot experiments, BacillusSYB1and B. megaterium JGB2increased radish yield up to55.89%and54.07%significantly. Bacillus QJB7increased canola yield up to30.24%. In the field experiment,Bacillus QJB7increased canola yield of up to24.30%. Bacillus DJB6increased freshweight of maize up to12.75%. Ochrobactrum pseudogrignonense DGB13increased freshweight of canola up to15.81%.5. Seven growth-promoting fungal strains were screened. In the field experiment,Colletotrichum GYF14and Fusarium oxysporum DJF12increased radish yield up to21.84%and28.99%. Colletotrichum QYF17increased fresh weight of radish up to7.32%.Chaetomium globosum DJF5increased fresh weight and plant height of maize up to11.09%and17.56%, respectively.6. Total12inorganic phosphate-solubilizing bacterial strains were screened. Amongthem Acinetobacter calcoaceticus GYB3increased fresh weight of maize up to14.75%,Escherichia DJB1and DGB11and Acinetobacter calcoaceticus DJB2increased freshweight of canola up to56.04%,41.86%and30.87%, respectively. One nitrogen-fixing bacterium GYB1was identifield as Klebsiella oxytoca, it increased fresh weight of canolaand maize up to59.96%and27.15%, respectively.