Effects of saline-alkali stress on bacterial and fungal community diversity in Leymus chinensis rhizosphere soil

The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and are grown in saline-alkaline environments. Their rhizosphere microorganisms contribute significantly to plant stress tolerance. To study bacterial and fungal community structure changes in Chinese ryegrass (Leymus chinensis) rhizosphere soil under salt and alkali stress, pot experiments were conducted with different salt and alkali stress intensities. High-throughput sequencing was conducted, and the microbial diversity, community structure, and driving factors were analyzed in rhizosphere soil. The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and grow in saline-alkaline environments. A total of 549 species of bacteria from 28 phyla and 250 species from 11 phyla of fungi were detected in the rhizosphere soil of Leymus chinensis with different saline-alkali gradients. Alpha diversity analysis along saline-alkali gradients showed that bacterial community richness and diversity were the highest in the moderate saline-alkali group (pH = 8.28, EC = 160.4 μS·cm⁻¹), while fungi had high richness and diversity in the control group (pH = 7.35, EC = 134.5 μS·cm⁻¹). The bacteriophyta Proteobacteria, Acidobacteria, Plantomycetes, and the eumycota Ascomycota, Basidiomycota, and Glomeromycota were found with relative abundances of more than 10%. Saline-alkali gradients had significant effects on the abundance of the bacterial and fungal groups in the rhizosphere. The distribution of bacterial colony structure was not significant at the species level (P > 0.05). However, there were significant differences in the distribution of fungal structure and considerable differences in the composition of fungal species among the moderate saline-alkali group, severe saline-alkali group, and control group (P < 0.05). Correlation analysis showed that the bacterial phylum Gemmatimonadetes had a highly significant positive correlation with pH and EC (P < 0. 01). Saline-alkali stress significantly inhibited the abundance of the bacteria Latescibacteria, Cyanobacteria, and Bacteroides, and the fungi Zoopagomycota, Mortierllomycota, and Cryptomycota (P < 0. 05). Compared with fungi, bacterial community composition was most closely correlated with soil salinization. This report provided new insights into the responses of relationships between rhizosphere soil microorganisms and salt and alkali tolerance of plants.