Shoot specific fungal endophytes alter soil phosphorus (P) fractions and potential acid phosphatase activity but do not increase P uptake in tall fescue

Aims: An experiment was performed to test how different fungal endophyte strains influenced tall fescue’s ability to access P from four P sources varying in solubility. Methods: Novel endophyte infected (AR542E+ or AR584E+), common toxic endophyte infected (CTE+), or endophyte-free (E-) tall fescues were grown for 90 days in acidic soils amended with 30 mg kg⁻¹ P of potassium dihydrogen phosphate (KH₂PO₄), iron phosphate (FePO₄), aluminum phosphate (AlPO₄), or tricalcium phosphate ((Ca₃(PO₄)₂), respectively. Results: Phosphorus form strongly influenced plant biomass, P acquisition, agronomic P use efficiency, microbial communities, P fractions. P uptake and vegetative biomass were similar for plants grown with AlPO₄, Ca₃(PO₄)₂, and KH₂PO₄ but greater than in control and FePO₄ soils. Infection with AR542E+ resulted in significantly less shoot biomass than CTE+ and E- varieties; there was no influence of endophyte on root biomass. The biomarker for arbuscular mycorrhizal fungi (AM fungi, 16:1ω5c) was selected as an effective predictor of variations in P uptake and tall fescue biomass. Potential acid phosphatase activity was strongly influenced by endophyte x P form interaction. Conclusions: Endophyte infection in tall fescue significantly affected the NaOH-extractable inorganic P fraction, but had little detectable influence on soil microbial community structure, root biomass, or P uptake.