Phosphate-Solubilizing Bacteria with Contrasting Arsenate Tolerance Sustain Phosphorus Nutrition and Restrict Arsenic Translocation in Peanut

Arsenate [As(V)] competes with phosphate for uptake, creating a challenge for peanut production in P-limited, As-affected agricultural systems. We investigated whether phosphate-solubilizing plant growth-promoting bacteria (PS-PGPB) with contrasting As(V)-tolerance phenotypes remained functional and benefited peanut when coinoculated with Bradyrhizobium sp. SEMIA6144. We screened four PS strains: native Enterobacter sp. J49, Serratia sp. S119, and Serratia sp. J260; and commercial Pseudomonas pergaminensis PMT1. J49 and PMT1 tolerated millimolar As(V), whereas S119 and J260 were inhibited at micromolar concentrations. As(V) increased soluble P in J49 and PMT1, maintained it in S119, and decreased it in J260. In J49 and S119, As(V) increased arsenate reductase and superoxide dismutase activities, but only S119 showed lipid peroxidation and induced glutathione-related enzymes, revealing different redox responses under strain-specific exposure conditions. Despite this divergence, both strains converged in planta. At a regionally relevant 3 µM As(V), coinoculation with either strain increased shoot P concentration in tricalcium phosphate (PTC)-supplied plants relative to PTC alone and restricted shoot As to below the method detection limit without significantly reducing root As concentrations. Nevertheless, As accumulated in nodules with J49 but remained undetected with S119. These findings identify integrated strain–plant–rhizobium performance as a key criterion for selecting inoculants that couple P acquisition with restriction of detectable total As translocation to shoots.