In vitro GROWTH OF ECTOMYCORRHIZAL FUNGI ASSOCIATED WITH Pinus radiata PLANTATIONS IN CHILE

A comparative study of in vitro growth of three species of ectomycorrhizal fungi (ECMF) (Rhizopogon luteolus, Suillus granulatus and Suillus luteus) was performed. Fungal material was collected in adult Pinus radiata plantations. Isolation and purification of the strains were performed on potato-dextroseagar medium and the evaluation of the radial growth rate and the increase in mycelial biomass, under different culture conditions, was performed on the Modified Melin Norkrans growth medium. The effects of temperature (24, 28 and 32 degrees C) and pH (4.8, 5.3, 5.8, 6.3 and 6.8) of the growth medium were tested for the three fungal species in two independent assays. The results indicate that the temperature had a significant effect on the radial growth rate (RG) and mycelial biomass increase (MB) in all of the evaluated fungal species. The highest RGR and MBI were recorded in R. luteolus, and the lowest values for these variables were registered in S. luteus. Rhizopogon luteolus had the highest sensitivity to pH changes. Meanwhile, there was no pattern in S. granulatus and S. luteus growth response under different pH conditions. When cultivated in vitro, the three studied species of ECMF presented adaptation, exponential, declining and stationary growth phases. The in vitro growth responses recorded in the present study showed the great potential of R. luteolus to be used in future programs using mycorrhizal inoculation in the production of Pinus radiata trees in nurseries in Chile.