β tricalcium phosphate

β-Dicalcium silicate (β-Ca₂SiO₄) was synthesized in the Shanghai Institute of Ceramics laboratory at the Chinese Academy of Sciences [7 (link)]. β-Tricalcium phosphate (Sigma, USA) was purchased from Sigma.

Modified Pikovskaya agar medium was used to determine the phosphate solubilisation capacity (Nopparat et al. 2009 ). The base solution (BS) was composed of (NH₄)₂SO₄ (0.5 g), KCl (0.2 g), MgSO₄.H₂O (0.1 g), MnSO₄.H₂O (0.004 g), FeSO₄.7H₂O (0.002 g), NaCl (0.2 g), D-glucose (10 g, Sigma-Aldrich), yeast extract (0.5 g, Kasvi, Brazil), bacteriological agar (18 g, Acumedia, USA), and distilled water (900 mL). The pH was adjusted to 6.8. The first phosphate solution (PS1) was composed of xanthan gum (0.5 g, Sigma-Aldrich), Ca₃(PO₄)₂ (0.5 g, β-tricalcium phosphate, Sigma-Aldrich) and distilled water. For the second solution (PS2), calcium phosphate was replaced with bone meal (0.5 g). All solutions were autoclaved (15 min at 121°C), mixed (BS+ PS1 and BS + PS2; pH adjusted to 6.6), and transferred to petri dishes.
To evaluate the growth of endophytes under different phosphorous sources, 6-mm plugs of each fungus were inoculated in petri dishes with BS+PS1 and BS+PS2 and incubated at 28°C for 7 days. The diameter of the halo surrounding the fungal colony and the colony diameter were measured daily using a graduated ruler (cm). The relative solubilisation efficiency was calculated as the diameter of solubilisation halo/diameter of colony × 100, using the mean of five replicates.