Screening and identification of five saline-alkali tolerant bacteria for growth promotion of red adzuki bean

Abstract:

[Background] Daqing is located in Songnen plain, which land is heavily salinized. Saline-alkali soil contains a large number of saline-alkali-resistant strains, some of which have special functions of promoting growth and can be used as beneficial bacteria to promote plant growth and improve plant saline-alkali-resistance. [Objective] In order to solve the problem of land salinization effectively and increase the yield of grain crops. [Methods] The saline-alkali soil collected in Daqing area as an experiment material was used to separate the saline-alkali tolerant bacteria under pH 9.0, 50 mmol/L NaHCO3, the growth promoting function of the strain was screened by functional medium, and the yield of corresponding substance was measured accordingly. The strains with complete promoting function and better promoting effect was selected, using analyses of morphology, physiological biochemistry, 16S rRNA gene sequence to identify the strains, so as to determine their taxonomic status. The growth promoting strains were tested on physiological indicators such as germination rate, root length, bud length, rooting number and root length of seeds of red adzuki bean to verify the growth promoting effect under pH 8.5 and 15 mmol/L NaHCO3. [Results] The strain 29 was Zobellella, and the others were Halomonas. All the five strains had the functions of nitrogen fixation and produced indole-3-acetic acid (IAA) and ACC deaminase. The strain 34 and strain 23 had the highest yield of IAA and ACC deaminase, reaching 17.66 mg/L and 0.31 U/mg respectively. In addition, the strain 23 was capable of producing siderophore, which content was 3.19%. The strains 29 and 41 had the ability of organophosphorus-dissolving and the phosphorus solution capacity is 20.05 mg/L and 34.61 mg/L. The results of plant growth promotion test showed that the germination rate and root length of red adzuki bean seeds were increased respectively by 41.67% and 32.63% after the seeds were treated with inoculation under saline-alkali stress. After inoculation, the root length and root number of seedlings increased by 129% and 160%, respectively, compared with saline-alkali stress control. [Conclusion] The five saline-alkali tolerance and growth-promoting bacteria could alleviate the inhibition of saline-alkali stress on the growth of red adzuki bean and promote the growth of its root system. This provides an excellent strain for the development of saline-alkali tolerant and growth-promoting microbial fertilizer.