Effect of inoculation and substrate disinfection method on rooting and ectomycorrhiza formation of Douglas fir cuttings

Abstract

Ectomycorrhizal inoculation techniques were applied to Douglas fir (Pseudotsuga menziesii (Mirb) Franco) cuttings, dur- ing the rooting phase, to determine the effect of inoculation on rooting and mycorrhizal colonization. Two experiments were con- ducted: 1) an inoculation experiment, established at three different locations with the same treatments, to determine the effect of inoc- ulation with Laccaria bicolor, Melanogaster ambiguus and Rhizopogon subareolatus; and 2) a local factorial experiment to determine the effect of fungal inoculation, substrate disinfection methods, and their possible interactions. At Peyrat-le-Château and Champenoux (France), there were no differences in rooting due to the inoculation treatment. At Cabrils (Spain), the cuttings inoculated with L. bicol- or and R. subareolatus rooted significantly better than non-inoculated cuttings. Vegetative inoculum of L. bicolor and spores of R. subareolatus were effective in forming ectomycorrhizas in the three locations, whereas spores of M. ambiguus were effective only at Cabrils. Substrate disinfection with methyl bromide significantly decreased the percentage of rooted cuttings compared to steam-dis- infected substrate. Methyl bromide application also lowered the percentage of mycorrhizal cuttings after inoculation with L. bicolor and R. subareolatus. The disinfection method did not alter significantly the colonization level among the mycorrhizal plants. (@ Inra/Elsevier, Paris.)