Testing of microbial additives in the rooting of Norway spruce (Picea abies [L.] Karst.) stem cuttings

Laboratory-produced alginate-bead inoculum of ectomycorrhizal (ECM) fungi Cortinarius sp. and Gomphidius glutinosus, fungal commercial products ECtovit® and Trichomil®, bacterial commercial product BactoFil B®, and commercial rooting stimulator Vetozen® were applied to a peat-perlite (1:2, v:v) rooting substrate of Norway spruce stem cuttings collected from 4-year-old nursery-grown seedlings immediately before the insertion of cuttings into the substrate. The application of beads free of fungi and the substrate without an additive were the other treatments. The cuttings were rooted in vessels (60 cuttings per vessel, 180 per treatment) placed in a glasshouse and arranged in a randomized complete block design. The cuttings were estimated for one growing season (approximately for 26 weeks) after their insertion into the rooting substrate. Rooting % of the cuttings ranged from 45 (mycelium-free beads) to 75 (control) according to treatments, 64 on average. No significant differences among treatments were found in % of ECM morphotypes, total ECM colonization of roots (%), and growth parameters of shoots and roots of the cuttings. The applied microbial additives were not sufficiently efficient to form treatment-related ectomycorrhizas that were formed by naturally occurring ECM fungi. Inoculation by the ECM fungus Cortinarius sp. and application of Trichomil had a partial stimulative effect on the shoot growth of cuttings. Shoot and root growth parameters were not significantly correlated with total ECM colonization, except for a negative dependence of the root number in Trichomil treatment. A higher concentration of K but lower concentrations of Ca and Mg in Ectovit treatment than in the other treatments were detected.