Screening and identification of salt-tolerant promoting bacteria of the rhizosphere of Suaeda dendroides in Xinjiang

Abstract:

[Background] Xinjiang is the largest salinized soil distribution area in China. Soil salinization inhibits plant growth seriously. Salt-tolerant promoting bacteria can improve soil fertility, crop stress resistance and soil utilization effectively, thus it promotes plant growth. [Objective] We isolated and screened salt-tolerant strains from rhizosphere soil of Suaeda dendroides. The strains with excellent growth-promoting effect were identified, and the microbial resources were excavated. [Methods] The traditional method of separation was used to screen the salt-tolerant bacteria in the rhizosphere of S. dendroides. The strains of salt-tolerant promoting bacteria were obtained through the three-stage screening system. DNA of the strains was extracted by CTAB method, and the 16S rRNA gene sequencing was performed for phylogenetic analysis to determine the classification status of the salt-tolerant bacteria. [Results] A total of 58 salt-tolerant bacteria were isolated from the rhizosphere of S. dendroides. There were 8 strains with nitrogen fixation activity, 12 strains with phosphate solubilizing activity, and 15 strains with potassium solubilizing activity, 3 strains with IAA activity, and 2 strains with strong ammonia producing ability. Strains named GTZW50-5 and MH-F promoted the growth of Arabidopsis thaliana significantly. The results of wheat pot experiment showed strain GTZW50-5 had significant growth promotion effect on root length and plant height of wheat, and to some extent, the chlorophyll content in plants was improved. Strain MH-F had a significant promoting effect on the roots of wheat, and the chlorophyll content and proline content of wheat were increased at different salt concentrations. According to phylogenetic analysis, the similarity between GTZW50-5 and Bacillus vallismortis (AY603658) was 99.43%, GTZW50-5 was identified as Bacillus vallismortis. The similarity between MH-F and Enterobacter ludwigii (JTLO01000001) sequence was 98.34%, which was identified as Enterobacter. [Conclusion] Strains GTZW50-5 and MH-F had a good effect of promoting growth, providing a theoretical basis for the development and utilization of salt-tolerant microbial resources.