Impacts of Arbuscular Mycorrhizal Fungi and Pseudomonas putida Interactions on the Protein content, Antioxidant Activities, and Cell Wall Remodeling of Strawberry

Phosphorus (P) availability is a major determinant of plant–microbe interactions, yet the combined effects of arbuscular mycorrhizal fungi (AMFs) and Pseudomonas putida under contrasting P regimes remain poorly understood. This study investigated three AMF species, Funneliformis mosseae (AMF1), Funneliformis caledonium (AMF2), and Acaulospora laevis (AMF3), alone or in combination with P. putida in strawberry plants grown under no P addition, insoluble P, and available P conditions. Root colonization, plant growth, P uptake, enzyme activity, protein accumulation, and cell wall composition were assessed. The results showed that inoculation outcomes were strongly context-dependent. AMF colonization was highest under insoluble P, particularly with AMF2 (51%), but was reduced by P. putida co-inoculation except under available P, where bacterial activity enhanced colonization. Plant biomass increased under insoluble P in dual inoculations, with P. putida  + AMF1 and P. putida  + AMF2 producing the greatest growth, suggesting synergistic P solubilization and transfer. Phosphorus uptake patterns indicated that dual inoculations promoted shoot P accumulation under insoluble P but sometimes led to localized P deficiencies under no P or high P. Biochemical responses included reduced phenylalanine ammonia-lyase (PAL) activity, increased protein content, and context-specific changes in peroxidase activity. FTIR spectroscopy confirmed extensive remodeling of cell wall carbohydrates, proteins, and phenolics, especially under insoluble P and dual inoculations. These findings highlight the ecological plasticity of AMF-bacteria interactions and demonstrate their potential to enhance nutrient acquisition, stress adaptation, and root structural modifications under P-limiting conditions, offering valuable implications for sustainable strawberry production.