Axenic Culture Growth Optimization of Adventitious Root Promoting Endophyte, Piriformospora indica

Biological solutions to common production problems are welcomed by growers and consumers as our society continues to raise its expectations for sustainability and reduced chemical inputs. A relatively new mycorrhizal-like fungi, Piriformospora indica, has shown promise to improve adventitious root formation, nutrient uptake, and disease resistance of various plant species.  One benefit of P. indica over other currently produced mycorrhizal products is the characteristic of being able to produce the fungi in pure culture without a plant host.  This aspect proposes the ease and feasibility of becoming a commercially produced product.  The objectives of this study were to determine: 1) the effect of temperature, light, and sugar concentration on radial mycelial growth in Potato Dextrose Agar (PDA); and 2) the effect of shaker speed (RPM), sugar concentration, and temperature on mycelial mass and chlamydospore production in Potato Dextrose Broth (PDB). In PDA experiments, temperatures between 5 °C and 40 °C at 5 degree intervals were tested.  The temperature producing the fastest radial growth was 25 °C.  PDA concentrations of 12 g/L, 24 g/L, and 48 g/L were evaluated. There was no significant difference between the growth rates for 12 g/L and 24 g/L, however, at 48 g/L growth was retarded.  Light had significant effects on mycelial growth. Full spectrum light retarded growth as opposed to  P. indica grown in the dark.   During liquid culture experiments, the optimal spore production speed was 150 RPM.  At 0 and 100 RPM few spores developed.   The P. indica was tested to see if sugar concentration had an effect on growth while shaken at 150 RPM.  Again, 48 g/L retarded growth and there was no significant difference between the growth rates for 12 g/L and 24 g/L.  Finally P. indica was grown at 20 °C, 25 °C and 30 °C, at 150 RPM, and in 24 g/L PDB concentration.  Significant mycelial mass and chlamydospores count occurred at 24 g/L PDB.