Alleviating salt stress on seedings using plant growth promoting rhizobacteria isolated from the rhizosphere soil of Achnatherum inebrians infected with Epichloë gansuensis endophyte

Soil salinity is a severe environmental stress, limiting plant growth and sustainable agriculture. Plant growth promoting rhizobacteria (PGPR) and Epichloe gansuensis endophyte can be used to alleviate the adverse effects of soil salinization, promote plant growth and improve resistance to biotic and abiotic stresses. The present study was conducted to investigate the diversity of culturable rhizosphere soil bacteria associated with Achnatherum inebrians, as well as the effect of E. gansuensis and PGPR on the germination of A. inebrians seeds under high concentrations of NaCl. The PGPR strains were obtained by traditional isolation and culture techniques, and then endophyte-infected and endophyte-free A. inebrians seeds exposed to different concentrations of NaCl were inoculated with PGPR. A total of 990 bacterial colonies were isolated, and these were assigned to 65 species within 18 genera and 4 phyla. Principal component analysis (PCA) indicated that the rhizosphere soil of A. inebrians plants with Epichloe had differing bacterial diversity from that without Epichloe. When A. inebrians seeds were exposed to NaCl concentrations of 0, 50, 100, 200 mmol/L, seed germination was enhanced at the low salt concentration (50 mmol/L) and inhibited at the highest salt concentration (200 mmol/L). E. gansuensis significantly (P < 0.05) promoted the germination and peroxidase (POD) activity of the seedlings under different NaCl concentrations. Inoculation with three selected isolates of rhizosphere bacteria significantly (P < 0.05) improved seed germination under the four different NaCl concentrations. This study provides new evidence that inoculation with PGPR of both endophyte-infected and uninfected A. inebrians seeds reduces the impact of NaCl stress on seed germination and provides a basis for further research on the mechanism of PGPR promotion of seed germination of A. inebrians.