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

Interactions between plant roots and nitrogen (N)-fixing microorganisms in the rhizosphere are crucial for plant growth and development. However, the contribution of rhizosphere microbial N fixation to peach tree growth and the underlying interaction mechanisms remain unclear. Our study demonstrated that peach trees under bag-controlled, precise, and stabilized low-N (BCLN) fertilization exhibited significantly increased root microbial abundance and soil N fixation. The peach rhizosphere soil showed significantly enhanced microbial α-diversity, increased abundance of N-fixing microbes, and elevated nitrogenase activity under BCLN fertilization. Further analysis indicated that BCLN fertilization induced peach roots to secrete arbutin, which mediated enrichment of the Pseudomonas strain DT33X, an N-fixing bacterium, thereby enhancing plant N-use efficiency (i.e., N accumulation relative to input). Arbutin, a component of root exudates, enhanced the growth, colonization, and N-fixation capacity of DT33X, as evidenced by an increased nifH gene copy number in soil. Together, these findings elucidate a mechanistic link between peach roots and N-fixing microbes under BCLN fertilization, demonstrating that specific root-derived signaling molecules can modulate N-fixing bacteria, thereby improving N-use efficiency in peach trees.