Bag-controlled low-nitrogen fertilization induces root arbutin secretion to enrich rhizosphere Pseudomonas for enhanced nitrogen fixation in peach

The interactions between the roots of plants and the nitrogen-fixing microorganisms in the rhizosphere are crucial for plant growth and development. However, the contribution of rhizosphere microbial nitrogen fixation to peach trees growth and the underlying interaction mechanisms remain unclear. Our study demonstrated that the peach trees under bag-controlled precise and stabilized low-nitrogen (BCLN) fertilization exhibited a significant increase in root microbial abundance and soil nitrogen fixation. The peach rhizosphere soil exhibited significantly enhanced microbial α-diversity, increased nitrogen-fixing microbial abundance, and elevated nitrogenase activity under BCLN fertilization. Further analysis showed that the BCLN fertilization induced peach roots to secrete arbutin, which mediated the enrichment of the Pseudomonas strain DT33X, a nitrogen-fixing bacterium, and thereby enhanced plant nitrogen-use efficiency. Arbutin, a component of the root exudate, enhanced the growth, colonization, and nitrogen-fixing capacity of DT33X, as evidenced by the increased copy number of the nifH gene in soil. Thus, we elucidated the mechanistic link between peach roots and nitrogen-fixing microbes under BCLN fertilization and found that specific root-derived signaling molecules regulated nitrogen-fixing bacteria, thereby improving nitrogen-use efficiency of the peach trees.