Phosphorus solubilization by ectomycorrhizal Pisolithus tinctorius in pure culture and in association with Acacia mangium

Abstract

Ability to utilize insoluble form of P by different isolates of ectomycorrhizal Pisolithus tinctorius (E3418, M270, Pt441 and P53) was observed from their growth on agar plates containing insoluble P (tricalcium phosphate). Inorganic P solubilizing efficiency and surface-bound and extra-cellular phosphatase activities were also measured in pure cultures. All the 4 isolates of P. tinctorius had significantly lower P concentration in their mycelia when grown on agar plates containing insoluble P. However, only the isolate E3418 showed poor mycelial production. The colony morphology (area and tissue density) of isolates M270 and Pt441 was significantly altered in the presence of insoluble P, while colonies of the isolate P53 did not show any change. Inorganic P solubilizing efficiency and phosphatase activities were highest in isolates P53 and Pt441, respectively. Ability to solubilize rock phosphate by different isolates of P. tinctorius when grown in association with Acacia mangium was also studied. Dry matter production, and N and P contents were significantly higher in P. tinctorius-inoculated A. mangium seedlings when compared to uninoculated seedlings. Seedlings inoculated with the isolate E3418 had significantly lower N and P contents when compared to seedlings inoculated with other isolates of P. tinctorius. Seedlings inoculated with isolates M270, Pt441 and P53 had similar N and P contents. However, seedlings inoculated with the isolate M270 produced significantly lower dry matter when compared to seedlings inoculated with isolates Pt441 and P53. The results are discussed in terms of variations in P solubilizing efficiencies, carbon consumption by ectomycorrhizal fungi, and carbon loss via the ectomycorrhizal hyphae. ©2005 Balaban.