A Quick Method for Metarhizium anisopliae Isolation from Cultural Soils

Abstract

Problem statement: Fungi are one of the most active members in biological community of cultural soils. Many saprophyte and facultative parasitic fungi live in soil. Metarhizium anisopliae, one of the most famous soil inhabitant entomopathogens has a virulence potential on plant and animal pests. Approach: Introducing a new method for its isolation from soil was an applied method to find it without any limitation. Metarhizium anisopliae shifts to saprophytic phase and remain alive within soil in absence of susceptible host. As a shortcut, we can transfer the fungus from soil to lab by culturing soil suspension. One hundred cultural soil samples from different regions of Iran were tested to finding Metarhizium isolates. Culturing 1:5000-1:10000 soil suspension on artificial medium containing necessary macro and micronutrients for fungal growth were resulted in isolation. Metarhizium anisopliae isolates were harvested seven days after culturing the suspensions. All isolates were inoculated in 50 mL PDB in destruxin production assay and 7 days later broth medium was filtrated by using filter paper. Culture filtrates were extracted and in bioassays they were sprayed on larva of citrus leaf miner. Results: Nine isolates of Metarhizium anisopliae were harvested. Microscopic studies showed that morphological features had complete coincidence with valid descriptions of the fungus. Bioassay confirmed that all harvested isolates secrete active and effective destruxin in broth. Conclusion: Isolation of Metarhizium by culturing the soil suspension, a useful method for more studies of the entomopathogen at different geographical regions. Native populations of this fungus had special importance in local biological control programs. This procedure was a costs- and time-effective method for pathogen isolation.