The viability and infectivity of an ectomycorrhizal inoculum (isolate UFSC-Rh90, Rhizopogon nigrescens), produced by submerged cultivation in an airlift bioreactor and immobilized in beads of calcium alginate gel, was studied. Inoculum remained 100% viable after 18 months in a 0.85% NaCl solution at 8 ± 1ºC. Mycelium grew from the beads after 48 h when they were placed on a solid culture medium at 25 ± 1ºC. Viability of pellets of non-immobilized mycelium stored under the same conditions decreased gradually after the third month of storage, reaching 0% by the 12th month. These pellets presented a gradual darkening, which was more intense in those located near the surface of the NaCl solution. In culture medium, these dark pellets showed no viability. Gel immobilization helps to maintain mycelium viability during storage and offers a physical protection when the inoculum is applied to the planting substrate. After eight months refrigeration, the immobilized inoculum was still able to infect Pinus taeda seedlings, colonizing an average of 37% of the root tips when inoculated in the plant growth substrate under greenhouse conditions. This inoculum presents a commercial potential to be produced and applied in forest nurseries.
Rhizopogon nigrescens; ectomycorrhizal fungus; submerged cultivation; Pinus taeda
