Plant growth-promoting rhizobacteria Bacillus velezensis JB0319 promotes lettuce growth under salt stress by modulating plant physiology and changing the rhizosphere bacterial community

Salt stress inhibits plant growth, which is an important factor that restricts crop yield. Plant growth-promoting rhizobacteria (PGPR) promote plant growth, but their effect on lettuce under salt stress has not been reported. In this study, the salt-tolerant growth-promoting bacteria Bacillus velezensis JB0319 in the plant rhizosphere was screened and used as microbial inoculum in a pot experiment to explore the effects of B. Velezensis JB0319 on growth, reactive oxygen scavenging, osmotic adjustment, and the rhizosphere bacterial community of lettuce planted in soils with different NaCl concentrations (0, 50, 100, 150 mM). B. Velezensis JB0319 inoculation significantly promoted the shoot height, root length and shoot biomass of lettuce, increased the activity of SOD, POD, decreased the accumulation of MDA in lettuce, and increased the accumulation of osmotic regulation substance SS, Pro. Most importantly, Inoculation B. Velezensis changed bacterial community structure in the rhizosphere of lettuce. The LDA analysis showed that B. Velezensis inoculation helped lettuce enrich more nitrogen-fixing bacteria. These results showed that B. Velezensis inoculation could alleviate the inhibitory effect of salt stress on lettuce and promote lettuce growth. This study provides a theoretical basis for plant growthpromoting rhizobacteria to alleviate salt stress in the future.