Endophytic colonization of Phomopsis liquidambaris recruits rhizospheric Ralstonia by inducing acetic acid secretion to facilitate phosphorus uptake by Arachis hypogaea L. in continuously cropped soil

Low phosphorus (P) use efficiency in continuously cropped peanut fields presents a major production constraint. Rhizosphere bacterial communities are critical for P cycling in terrestrial ecosystems. The role of interactions between plants and root endophytes in regulating rhizosphere P cycling via functional microbial communities remains unclear. Here, we quantified the impacts of changes induced by the root endophyte Phomopsis liquidambaris B3 on root exudate chemistry and the optimization of phosphate starvation regulon (phoD)-harboring bacterial communities.

Rhizosphere soil P fractions, phosphatase activity and bacterial population diversity were monitored throughout the growing season under two treatments: B3-colonized and B3-free conditions. Laboratory experiments were carried out to determine the influence of B3 colonization on the organic acid metabolic profiles of peanut roots and to link B3-induced changes in root chemistry with the chemotaxis and the growth of phoD-harboring bacteria.

Our study showed that B3 colonization enhanced peanut growth and improved the utilization efficiency of soil organic P (Po) by optimizing the community structure of soil phoD-harboring bacteria and recruiting the keystone Po-mineralization microorganism Ralstonia in the peanut rhizosphere. This bacterial community enhanced alkaline phosphatase (AKP) activity in the rhizosphere, promoting Po mineralization. Pure culture experiments revealed the key role of B3-induced root exudation of acetic acid in the optimization of the phoD-harboring bacterial community and the recruitment of the keystone microorganism Ralstonia.

Peanut inoculated with B3 recruits beneficial Ralstonia by exudating acetic acid that optimize the rhizosphere phoD-harboring bacterial community and facilitate P uptake of peanuts.