Studies On Bacterial Diversity And Antagonistic Growth - Promoting Characteristics Of Dendrobium Candidum

Dendrobium moniliforme (L.) Sw is a perennial herb, which flowers are graceful with ornamental value. The stems of D. moniliforme can heal fluid and stomach, lungs and cough, showing great value both in medicine and economy. Therefore, D. moniliforme has broad development prospects. In this study, wild plants of D. moniliforme were collected in Yingshan County, Hubei Province. In order to provide excellent solutions for D. moniliforme conservation and screened bacteria with excellent potential and growth-promoting activity, lay the foundation for bacterial GAP cultivation, the best medium for growth of D. moniliforme seedlings were screened and the diversity of the culturable D. moniliforme-associated bacteria and their plant growth-promoting potential were studied.In tissue culture research, seedlings of D. moniliforme with2cm height were selected as experimental materials. The effects of different hormones combinations and different supplements combinations on growth of D. moniliforme were tested. The results showed that6-BA and NAA in conjunction can promote the growth of D. moniliforme seedlings, when hormone ratio of0.5mg/L NAA+0.6mg/L6-BA, the seedlings grow well. In addition, coconut milk and potatoes leachate can significantly promote the extension and widening of leaves.The diversity of the culturable D. moniliforme-associated bacteria and their plant growth-promoting potential, including phosphorus solubilization, potassium solubilization, IAA production and siderophore production were investigated by ARDRA analysis and relevant tests. The results showed seventy five bacterial strains were obtained in total. Among these bacteria, twenty one strains were isolated form D. moniliforme, fourteen strains form the rhizosphere moss and forty strains form the rhizosphere soil. The ARDRA analysis revealed high diversity of these bacterial isolates.16s rDNA sequences indicated that the dominant bacteria were Bacillus sp. and Pseudomonas sp. In addition, twenty three strains showed abilities to dissolve inorganic phosphorus and organic phosphorus, twelve strains had fixing nitrogen ability, sixty four strains of bacteria can produce IAA, thirty nine strains of bacteria can produce siderophore and twenty five strains of bacteria had potassium solubilization ability. These bacteria belong to Streptomyces, Bacillus, Pseudomonas, Rahnella, Pandoraea, Microbacterium, Lysinibacillus and Pantoea.Furthermore,33bacteria strains were selected from each ARDRA clusters to tested antagonistic activity toward six pathogenic fungi. The results showed that strains DmBR2, DmB10, DmB6and DmB9performed antagonistic activity to all fungal pathogens and the strain DmB6was the best one. In chitinase, protease and cellulase activity assay, these four bacterial strains showed high production activity. In subsequent experiments, we can filter fine strain used in plant disease control, achieve environmental objectives.