Deciphering the role of crop genotypes and arbuscular mycorrhizal species in modulating hyphal microbiome under phosphorus stress

Phosphorus (P) is a limiting soil nutrient in many ecosystems due to complex formation with metals, leading to nutrient stress in plants. One of the strategies by which plants address P stress is by forming symbiosis with arbuscular mycorrhizal fungi (AMF). While AMF are known for acquiring and transporting accessible forms of P, their hyphae also support a diverse bacterial community, with some bacteria playing key roles in effective solubilization of P. Although this bacterial partnership could improve the symbiotic efficiency of AMF, the factors affecting the selection of bacteria across various plant genotype-AMF combinations are poorly understood. We investigated how different AMF species from various orders (Rhizophagus intraradices, Gigaspora margarita), alongside a non-AMF control, and three diverse sorghum accessions characterized by distinct root exudate profiles, impacted the root and hyphal microbiomes. The AMF hyphae had a higher prevalence of bacteria from Chloroflexi, Actinobacteria, and Proteobacteria, showing significant differences between the two AMF species; however, the roots displayed a greater abundance of Proteobacteria across all AMF species. Rhizosphere soils contained more organic acids, such as shikimic acid and succinic acid, as well as sugars such as sucrose, compared to hyphosphere and control soils. Additionally, hyphosphere soils were rich in mannitol, xylose, N-acetyl glucosamine, and 3-hydroxybutyric acid. Overall, our findings suggest that AMF species from different orders, each with unique life history strategies, distinctly influenced the diversity of hyphal bacterial communities.