Isolation Of Hydrogen-oxidizing Bacteria From The Rhizosphere Of Astragalus Adsurgens Pall And The Study Of Plant Growth Promoting Ability Of SDW-16

To obtain hydrogen-oxidizing bacteria with huge potential in plant growth promoting and explore the plant growth promoting mechanisms, to provide with high quality strain resources and theoretical basis for "H2-fertilizer" used in future. Hydrogen-oxidizing bacteria were isolated from the rhizosphere soil of Astragalus adsurgens Pall, through mineral salt medium plates in a gas-cycling incubation system with mixed gas of H2, O2, CO2. The TTC method was used for the detection of hydrogenase, while the determination of the capacity of production IAA was done by the method of Salkowski reagent, and the ACC deaminase activity was quantitative analysis by2,4-Dinitrophenylhydrazine colorimetry, the modified bistratal CAS plates was used in characterizing siderophore-producing strains, through the above characteristics of hydrogen-oxidizing bacteria that we canunderstand its’mechanisms preliminarily. High potential plant growth promoting strains were obtained with the ACC deaminase as the main reference and combined with other promoting tributes, and then the selected strains were classified by physio-biochemical tests and16S rDNA sequence analysis. The strains who have effect of growth-promoting and biocontrol were screened by plate confrontation method, then which was used in the research on the effect of promoting wheat growth.Though careful screening,39strains of bacteria were obtained. A total of15strains was confirmed to be hydrogen-oxidizing bacteria by TTC tested. The determination of growth promoting tributes showed that all strains can produce IAA(11.53-38.53ug/ml), a total of13ACC deaminase-positive strains were obtained, accounting for86.7%of the total hydrogen-oxidizing bacterial strains, the highest activity reached at8694.55nmol·g-1·h-1, and there are8strains of siderophore-positive. According to the results of physio-biochemical tests and16S rDNA sequence analysis, AaP-6and AaP-20were confirmed to be Microbacterium sp., while SDW-16was identified as Pseudomonas fluorescens. Only SDW-16showed antagonistic activities to the tested pathogens on the plate confrontation, so SDW-16was tested the effect of growth promoting on wheat. And SDW-16increased the plant height, root length, stem length, total fresh weight, root fresh weight, total dry weight and root dry weight of wheat by50.26%,191.67%,2.42%,76.57%,107.71%,35.11%and25.66%compared with the control group, among that the two parameters of root length and root fresh weight reached extremely significant difference, and the number and length of lateral roots and the amount of root hair also increased significantly (data not shown)The above results showed that the hydrogen-oxidizing bacteria in the rhizosphere of Astragalus adsurgens Pall generally have more than one tributes of plant growth promoting, and some growth promoting tributes is higher than other PGPR, that not only can help us understand the growth promoting mechanisms of hydrogen-oxidizing bacteria, but also show the research value of hydrogen-oxidizing bacteria in the rhizosphere of Astragalus adsurgens Pall. Especially the positive effect of growth promoting on wheat by SDW-16proved the existence of hydrogen-oxidizing bacteria with high potential in plant growth promoting, and provided high-quality stains in subsequent studies and theoretical basis for "H2fertilizer" research in the future.