Effect of application of vegetative inoculum of the symbiotic fungi to rooting substrate on rooting and biomass formation of Norway spruce (Picea abies [L.] Karst.) cuttings

The production of clonal plants using cuttings is the more traditional approach to mass vegetative propagation, with rooting and transplanting efficiency a major determining factors of method success. The most important forest tree species in Slovakia, first of all Norway spruce and also oak and beech can be routinely propagated as rooted cuttings in operational scale. Autovegetative propagation may be enhanced by mycorrhizal fungi through non-specific stimulation (metabolites of fungi) or specific stimulation (artificial mycorrhiza synthesis). Auxins, which could be produced also by ectomycorrhizal fungi, are known to improve root formation of cuttings in many species. Along with the associated symbiotic partners, environmental conditions (rooting substrate) and type and application method of inoculum affect the success of fungal inoculation of cuttings. In this study, vegetative fungal inoculum (vermiculite penetrated with mycelium) was mixed with upper layer of rooting substrate (peat-perlite mixture) immediately before planting of Norway spruce (Picea abies (L.) Karst.) cuttings. The effects of the three ectomycorrhizal fungi were tested: Lactarius deliciosus (L.) Gray, Hebeloma crustuliniforme (Bull.: St-Am.) Quel. and Hygrophorus piceae Kuhner. (Tab. 1). Rooting substrate amended with pure vermiculite (without mycelium) and control peat-perlite rooting substrate were the other experimental treatments. Cuttings were collected from dormant lateral shoots at beginning of April. The rooting substrate and the cuttings were disinfected with Fundazol 50 WP. Randomized complete block design with three replications was arranged. 60 cuttings per vessel (one replication within treatment) were planted. After the first growing season (in november) percentages of rooted cuttings from all planted ones were determined. 15 cuttings per replication of each treatment (45 per treatment) were randomly selected and evaluated for mycorrhizal colonization (% of number of mycorrhizae from total number of short roots), number, length and dry weight of shoots and roots outgrowing from basis of cuttings. Mycorrhization by vegetative fungal inoculum (vermiculite as carrier of mycelium) was not effective on rooting and ectomycorrhiza forrnation of cuttings (Fig. 1, Tab. 2, 3). The rooting percentages were 79, 73, 85, 71 and 84 for Lactarius, Hebeloma, Hygrophorus, pure vermiculite and control, respectively. Mycorrhiza development of inoculated plants was affected by naturally occurred competing mycorrhizal fungi. There were no significant differences in root and shoot characteristics between control peat-perlite sub strate and the other treatments (Tab. 2, 3). However, significantly higher number of roots and shoot dry weight of Hygrophorus inoculated cuttings than those planted to with pure vermiculite amended substrate were found. Significant difference between Hygrophorus and Hebeloma in number of roots was also recorded. As a preliminary conclusion, vegetative fungal inoculum with vermiculite as a mycelial currier appear to be available form for application of ectomycorrhizal fungi to rooting substrate of cuttings.