Fungal inoculum properties and its effect on growth and enzyme activity of Trametes versicolor in soil.

The effect of fungal inoculum properties on colonization of nonsterile soil by three isolates of the white-rot fungus Trametes versicolor was investigated. Fungal inoculum properties were examined in separate experiments and were fungal inoculum composition, age of fungal inoculum, concentration of the inoculum and inoculation method. The fungal inoculum composition study compared pine versus poplar sawdust as the basic carrier with varying amounts of corn grit, corn meal and starch. The age of the fungal inoculum studied ranged from 3 to 21 days. The inoculum concentration gradually increased from 0 to 50% (v/v). The study assessing inoculation method compared mixing with layering techniques. The effect of moisture conditions of soil, sawdust and sand in combination with two inoculation methods (mixing versus point source inoculation) on colonization by T. versicolor was also determined. Colonization of soil was always assessed visually and enzymatically monitoring mycelial growth, biological potential (fluorescein diacetate assay) and laccase levels. Generally, the three different assessment methods correlated (P < 0.05) with each other. A fungal inoculum based on pine sawdust supported white-rot fungal growth in soil better than a poplar sawdust basis. Colonization of soil by T. versicolor was improved by increasing the corn content of the fungal inoculum. Younger (<7 days old) fungal inoculum resulted in better soil colonization than older (>10 days). A strong correlation (P < 0.001) was observed between the amount of fungal inoculum used in the soil augmentation and white-rot fungal colonization of soil. Inoculation of the fungal inoculum into soil by mixing was preferable over application in layers or point source inoculation. Moisture level did not influence biological potential measurements, but affected mycelial growth and laccase expression.