The roots of most terrestrial plants form symbioses with a diversity of arbuscular mycorrhizal (AM) fungi, which make substantial contributions to plant phosphorus (P) uptake. Large genetic variation exists within AM fungi of the same species. However, the impact of these variations, on the mycorrhizal contribution to plants' P uptake by different isolates of the same species and the differences in physiological mechanism remain unknown. In the present study, we selected maize (genotype Oh 43) as the host plant and investigated the response of plant P uptake and soil organic P use efficiency to two different AM fungal isolates, Rhizophagus irregularis MUCL 41833 and R. irregularis MUCL 43194 at three soil P availability levels (10.3, 18.6, 43.3 mg kg⁻¹, representing low, medium and high soil available P level, respectively). We found that at the medium soil available P level, R. irregularis MUCL 41833 produced large amounts of extraradical hyphae to explore soil and induced greater expression of phosphate transporter gene ZmPHT1;6 involved in the mycorrhizal pathway. While, R. irregularis MUCL 43194 recruited a specific, and different, bacterial community in the rhizosphere compared to R. irregularis MUCL 41833. This shift in rhizosphere microbiome was characterized by the recruitment of a greater abundance of Betaproteobacteriales when the plant was colonized by R. irregularis MUCL 43194, which showed a strong positive correlation with alkaline phosphatase activity, and suggested a link to greater organic P mineralization. Collectively, our results suggest that the two isolates of R. irregularis have different strategies for improving plant P uptake at the medium soil available P level, which deepened our understanding on the contribution and complexity of the mycorrhizal pathway to plant P uptake.

大多数陆生植物的根部与多种丛枝菌根 (AM) 真菌形成共生体，这些真菌对植物磷 (P) 的吸收做出了重大贡献。同一物种的 AM 真菌中存在较大的遗传变异。然而，这些变化对同一物种的不同分离株对植物磷吸收的菌根贡献的影响以及生理机制的差异仍然未知。在本研究中，我们选择玉米（基因型 Oh 43）作为宿主植物，并研究了植物对磷的吸收和土壤有机磷利用效率对两种不同的 AM 真菌分离株的响应，即不规则根霉 MUCL 41833 和不规则根霉 MUCL 43194。土壤磷有效性水平（10.3、18.6、43.3 mg kg ^-1，分别代表低、中、高土壤有效磷水平）。我们发现，在中等土壤有效磷水平，不规则菌MUCL 41833产生大量的根外菌丝来探索土壤，并诱导参与菌根途径的磷酸盐转运蛋白基因ZmPHT1;6的更多表达。而与不规则根际 MUCL 41833相比，不规则根际 MUCL 43194 在根际招募了一个特定的、不同的细菌群落。根际微生物组的这种转变的特点是当植物被R. . 不规则的MUCL 43194 与碱性磷酸酶活性呈强正相关，表明与更大的有机磷矿化有关。总的来说，我们的研究结果表明，在中等土壤有效磷水平上，两种不规则菌根分离株在提高植物吸磷方面具有不同的策略，这加深了我们对菌根途径对植物吸磷的贡献和复杂性的理解。