Sporulation of several biocontrol fungi as affected by carbon and nitrogen sources in a two-stage cultivation system

Abstract

The development of fungal biopesticides requires the efficient production of large numbers spores or other propagules. The current study used published information concerning carbon concentrations and C:N ratios to evaluate the effects of carbon and nitrogen sources on sporulation of Paecilomyces lilacinus (IPC-P and M-14) and Metarhizium anisopliae (SQZ-1-21 and RS-4-1) in a two-stage cultivation system. For P. lilacinus IPCP, the optimal sporulation medium contained urea as the nitrogen source, dextrin as the carbon source at 1 g/L, a C:N ratio of 5:1, with ZnSO₄·7H₂O at 10 mg/L and CaCl₂ at 3 g/L. The optimal sporulation medium for P. lilacinus M-14 contained soy peptone as the nitrogen source and maltose as the carbon source at 2 g/L, a C:N ratio of 10:1, with ZnSO₄·7H₂O at 250 mg/L, CuSO₄·5H₂O at 10 mg/L, H₃BO₄ at 5 mg/L, and Na₂MoO₄·2H₂O at 5 mg/L. The optimum sporulation medium for M. anisopliae SQZ-1-21 contained urea as the nitrogen source, sucrose as the carbon source at 16 g/ L, a C:N ratio of 80:1, with ZnSO₄·7H₂O at 50 mg/L, CuSO₄·5H₂O at 50 mg/L, H₃BO₄ at 5 mg/L, and MnSO₄·H₂O at 10 mg/L. The optimum sporulation medium for M. anisopliae RS-4-1 contained soy peptone as the nitrogen source, sucrose as the carbon source at 4 g/L, a C:N ratio of 5:1, with ZnSO₄·7H₂O at 50 mg/L and H₃BO₄ at 50 mg/L. All sporulation media contained 17 g/L agar. While these results were empirically derived, they provide a first step toward low-cost mass production of these biocontrol agents.