Efficiency of mycelial inoculum of 17 fungal species to promote ectomycorrhizal colonization in containerized Pinus pinaster, Pinus radiata and Pseudotsuga menziesii seedlings

Abstract

The use of mycorrhizal seedlings would improve the plant performance in revegetation and reforestation. Nevertheless, the use of these ectomycorrhizal fungi, at a commercial scale, will not be possible until practical and efficient methods of inocula production and application are developed. In the present work, different experiments of controlled mycorrhization have been performed to determine suitable inoculation methods, and dosages of application, for the production of containerized mycorrhizal seedlings of three forest species: Pinus pinaster, Pinus radiata and Pseudotsuga menziesii. Of the 20 isolates tested, six formed ectomycorrhizas with at least one of the tree species. The best results were obtained with the isolates of: Hebeloma crustuliniforme, Laccaria bicolor and Laccaria laccata, using either mycelial inoculum grown in peat-vermiculite or mycelium entrapped in alginate beads. Hebeloma isolates performed the best when mycelium grown in peat-vermiculite was used, whereas Laccaria isolates were more efficient when applied as mycelium entrapped in alginate. The optimal application dosages varied with each plant and fungus combination, but in most cases levels around 50 p. 100 of mycorrhizal feeder roots were obtained using inocula concentrations ranging from 1:32 to 1:64 (inoculum:substrate, v:v). In specific cases, such as mycelia of Laccaria laccata entrapped in alginate beads, the inoculum dosage could be reduced to 1:80 or even 1:160.