Bacillus velezensis SQR9 promotes plant growth through colonization and rhizosphere-phyllosphere bacteria manipulation

The rhizosphere and phyllosphere of plants harbor diverse microorganisms that play crucial roles in ecosystem services. Hence, plant growth-promoting bacteria (PGPB) have been widely used as inoculants to promote plant growth and improve productivity. However, to date, the interactions between the rhizosphere and phyllosphere that are influenced by PGPB inoculation remain understudied. Here, we inoculated Bacillus velezensis SQR9 as a PGPB in the bulk soil, rhizosphere or phyllosphere and then investigated the bacterial communities in the rhizosphere and phyllosphere through amplicon sequencing. The results showed that the inoculation of PGPB increased its abundance in the corresponding compartment, and all the treatments showed plant growth promotion effects. Further analysis of sequencing data also showed that the presence of PGPB had a greater effect on bacterial communities in both the rhizosphere and phyllosphere than in the inoculation compartment. Importantly, similar rhizosphere beneficial microbes were stimulated by the PGPB regardless of where it was inoculated. Therefore, we conclude that PGPB can promote plant growth both directly and through the rhizosphere-phyllosphere interaction, which lead to the enrichment of beneficial microorganisms.