Diversity Analysis Of Endophytic Bacteria And Culture Potential

Dendrobium loddigesii Rolfe, the plant of Dendrobium Sw. in Orchidaceae, mainly distribute in Guangxi, Guangdong, Guizhou and Yunnan. The species always shows medical and ornamental value. However, due to the long growth cycle, the low reproduction coefficient and overexploitation, D. loddigesii wild resources are at the risk of extinction. It is important to protect this endangered plant. This study composed of three aspects:the suitable prescription for rooting, the diversity of plant endophyte, the plant-growth-promoting potential of endophytic bacteria. Our studies can provide a theoretical basis and technical support of D.loddigesii plantlets industrial production and bio-fertilizer which has growth-promoting effect.1. The suitable prescription for rooting.In this study, the best rooting medium was selected according to orthogonal test. D.loddigesii plantlets were selected as materials, selected different concentration of nitrogen and phosphorus was first step and then different hormone was used to filter the best medium for rooting. Results showed that1/2MS (N/P=3:2)+0.5mg/L IB A+0.5mg/L NAA+0.05%AC was the best additive.2. The diversity of plant endophyte.The endophyte in root, stem and leaf was isolated from D.loddigesii in Guangxi, Yunnan and Guangdong. Results showed that14endophytic fungi and67endophytic bacteria were obtained from all locations, and their distribution characteristics showed specificity of region and tissue. In which, numbers of endophyte strains in plants collected from Guangxi was the most (fungi:9, bacteria:42) and that isolated from stems was the most (fungi:5, bacteria:34). After sequence alignment, we concluded that those endophytic fungi belong to Fusarium, Tulasnella, Cylindrocarpon, Arthrinium, Xylariales.3. The plant-growth-promoting potential of endophytic bacteria.In67endophytic bacterium strains,30strains possess double activities of solubilizing inorganic and organic phosphorus,22strains do the solubilizing potassium activity and24strains do the producing IAA activity, in which, only8strains possess all of three plant-growth-promoting activity. Result of tissue culture experiment shows that106cfu/mL DLB20strain of Bacillus is inoculated on the medium, which can promot growth of D.loddigesii plantlets with height of2-3cm and3-4cm, and is beneficial to rooting of plantlets with height of3-4cm, meaning that the strains with activities of solubilizing phosphorus, solubilizing potassium and producing IAA possess the pant-growth-promoting potential to D.loddigesii plantlets.