Phosphate source interacts with endophyte strain to influence biomass and root system architecture in tall fescue

Endophyte infection in tall fescue has been associated with greater P uptake. This study was designed to determine the influence of endophyte genotype on the ability of tall fescue to mobilize inorganic phosphorus (Pi) from four Pi sources (KH₂PO₄[K-Ps], FePO₄ [Fe-Ps], AlPO₄ [Al-Ps] and Ca₃(PO₄)₂ [Ca-Ps]). Tall fescue infected with three different endophytes (CTE+, AR542E+, and AR584E+) and endophyte free (E-) were grown in growth media amended with four P sources at three P levels (control, low 0.31 mg/L, and high 31 mg/L) for 3 wk after which root system architecture, P uptake, and dry biomass were determined. The P source and P concentration had the most influence on plant growth and P uptake. Endophyte and the interaction between P source and endophyte strongly influenced shoot and total dry mass in P-limiting conditions. Greater P uptake was found in plants grown with Ca-Ps compared to the other Pi sources and control treatments, regardless of P level and endophyte status. Endophyte-infection, irrespective of type, resulted in more plant biomass (dry matter, DM) than non-infected tall fescue in low K-P treatment. Longer roots, greater surface area and root/shoot ratio in high Fe-Ps level than those in other P treatments, but lower P uptake were observed, regardless of endophyte status. Morphological changes in the roots system of tall fescue due to endophyte infection were influenced by P source.