Effects of peach tree root extracts on the growth of replanted peach tree and soil microbial community

【Objective】Peach [Prunus persica (L.) Batsch] is a globally cultivated fruit crop and possesses high economic importance. However, continuous monocropping frequently leads to peach replant disease, a pervasive problem characterized by inhibited seedling growth, rhizosphere disorder, reduced productivity, and orchard degradation. Increasing evidence suggests that allelopathic autotoxic substances released from senescent root residues may act as key triggers, inducing shifts in rhizosphere microbial composition, suppressing nutrient cycling, and negatively affecting plant physiological processes. Nevertheless, the comprehensive spectrum of peach root-derived autotoxic metabolites and their cascading effects on rhizosphere microecology and seedling development remain insufficiently characterized. This study aimed to elucidate the composition of autotoxic allelochemicals in peach roots, evaluate their impacts on soil nutrient availability, microbial community dynamics, and photosynthetic and morphological performance of peach seedlings, and clarify their potential role in the development of peach replant disorder. The findings are intended to support mechanistic interpretation and provide a theoretical foundation for designing effective replant mitigation strategies.【Methods】Root samples were collected from an aged peach orchard and processed into high (1∶10) and low (1∶40) concentra-tion aqueous extracts. Non-targeted metabolomic profiling was conducted using a mass spectrometrybased platform to identify autotoxic compounds present in peach roots. A pot experiment was established using distilled water as the control to assess rhizosphere soil properties and seedling responses under extract treatment. Soil enzyme activity (urease) was determined via a colorimetric assay. Available phosphorus and potassium were quantified using flame photometry, soil organic matter content was assessed using an oxidation method, and available Fe, Mn, and Zn were determined via atomic absorption spectrophotometry. Bacterial and fungal community structures were analyzed through high-throughput sequencing using specific primers. A portable photosynthesis system was used to measure net photosynthetic rate. Root morphology was quantified using a root scanner, and root activity was assessed using the TTC (triphenyltetrazolium chloride) reduction method. Statistical and correlation analyses were conducted to clarify interactions among metabolite accumulation, soil ecological changes, and seedling physiological responses.【Results】A total of 1133 metabolites were identified from peach roots. These compounds predominantly consisted of phenolic acids and their derivatives (e.g., benzoic acid, phenylpropionic acid, cinnamic acid, caffeic acid), organic acids, coumarins, flavonoids (such as flavanols, flavonoid glycosides, isoflavones, and catechins), alkaloids (including quinolizidine and indole alkaloids), quinones (e.g., benzoquinones, naphthoquinones, anthraquinones), terpenoids (monoterpenes, sesquiterpenes, other terpenoids), and hormone- like substances (e.g., jasmonic acid, abscisic acid). Many of these compounds are widely recognized as allelochemicals with autotoxic or antimicrobial potential. Root extract application significantly altered the soil biochemical environment. Both extract concentrations markedly reduced soil urease activity and available phosphorus content, indicating suppressed nitrogen and phosphorus cycling. Extracts also altered micronutrient availability, particularly increasing Fe and reducing Zn content. Bacterial community richness and diversity decreased significantly, suggesting strong inhibitory pressure on beneficial rhizobacteria. Fungal communities showed concentration- dependent shifts: low extract concentration simplified both bacterial and fungal structures, while high concentration increased fungal community complexity, particularly promoting potential pathogenic taxa. Pathogen-associated phyla such as Pseudomonadota, Olpidiomycota, and Rozellomycota were significantly enriched under high extract treatment, indicating a transition toward a disease-favoring rhizosphere state. Peach seedling growth was markedly inhibited by root extract exposure. Root morphological indicators, including total root length, root volume, root tip number, root activity, and root dry mass, were all significantly reduced, with stronger suppression observed under high extract concentration. Aboveground traits such as plant height, stem diameter, and leaf area were negatively affected, accompanied by significant reductions in chlorophyll a, chlorophyll b, and carotenoid contents, implying impaired photosynthetic capacity. These responses indicate that root-derived autotoxic compounds disrupt the rhizosphere ecological balance, impair nutrient bioavailability, suppress root growth and activity, reduce photosynthetic pigment synthesis, and ultimately limit overall seedling vitality. A potential inhibitory pathway is proposed as follows: peach root allelochemicals → disturbance of microbial community structure → reduction in nutrient transformation and enzyme activities → impaired root uptake efficiency → reduced photosynthesis → inhibited seedling growth.【Conclusion】Peach roots harbor a diverse array of autotoxic substances, including phenolic acids, flavonoids, coumarins, alkaloids, quinones, terpenoids, and hormone-like compounds. These metabolites contribute to replant disorder by altering soil enzyme activity and nutrient availability, restructuring rhizosphere microbial diversity, promoting pathogenic microbial proliferation, and impairing root system development and shoot physiological performance. The inhibitory effects are concentration-dependent, with high-concentration root extracts exert-ing greater negative impacts. This study provides novel mechanistic insights into the autotoxicity-microbiome interaction model associated with peach replant disease and highlights the importance of regulating rhizosphere chemical and microbial homeostasis. The results offer a theoretical framework for mitigating peach replant obstacles through strategies such as selective rootstock utilization, rhizosphere microbiome reconstruction, and organic amendment application. Furthermore, the findings lay a foundation for future development of targeted autotoxicity detoxification and microbial regulation models to promote sustainable peach orchard renewal.