Some studies indicate that metal nanoparticles can be used in plant cultivation as fungicides and growth stimulators. The aim of this study was to evaluate the effect of silver (AgNPs) and copper nanoparticles (CuNPs) on the growth parameters, on the extent of leaves infected by powdery mildew and on spontaneous ectomycorrhizal colonization of English oak (Quercus robur L.) seedlings growing in containers. Nanoparticles were applied to foliage four times during one vegetation season, at four concentrations: 0, 5, 25 and 50 ppm. The adsorption of NPs to leaves was observed by microscopical imaging (TEM). The tested concentrations of AgNPs and CuNPs did not have any significant effect on the growth parameters of the oak seedlings. TEM results showed disturbances in the shape of plastids, plastoglobules and the starch content of oak leaves treated with 50 ppm Cu- and AgNPs, while no changes in the ultrastructure of stems and roots of oak plants treated with NPs were observed. No significant difference in powdery mildew disease intensity was observed after NP foliar app lication. Four ectomycorrhizal taxa were detected on oak roots (Sphaerosporella brunnea, Thelephora terrestris, Paxillus involutus and Laccaria proxima). Oak seedlings treated (foliar) with CuNPs and AgNPs at 25 ppm were characterised by the highest degree of mycorrhization (respectively, 37.1% and 37.5%) among all treatments including the control treatment. None of the tested NPs manifested phytotoxicity in the examined Q. robur seedlings under container nursery conditions.

Every year there are changes in the register of fungicides available for forestry. It is proactive to develop a new strategy to minimise the application of chemical methods and replace them with natural and biological fungal control options. This study compares the influence after one growing season in a bare-root forest nursery of (a) effective microorganisms (EM) consisting of mixed cultures of beneficial and naturally-occurring microorganisms, (b) the organic fertilizer Actifos (Act), and (c) the mineral fertilizer Busz Forte (BF) on the growth and mycorrhizal colonization of two common forest deciduous tree species: Fagus sylvatica and Quercus robur. None of the analysed growth parameters (root collar diameter, length of shoots and roots, dry mass of shoots, and roots) of either tested tree species differed significantly among treatments. For both tree species, seedlings treated with EM exhibited partnerships with a smaller species richness of mycorrhizae than did seedlings in other treatments. Moreover, EM treatment significantly increased the abundance of non-vital root tips for both species. By contrast, BF exerted a negative effect on F. sylvatica non-vital mycorrhiza abundance. Based on morphological and molecular identification, a total of 11 ectomycorrhizal (ECM) fungal taxa were detected in this study; three species (Peziza ostracoderma, Scleroderma areolatum and Cenococcum-like) were shared between both plant species. Across treatments, the most abundant ECM fungal species on F. sylvatica roots were Pezizaceae sp. (51.1%) and Hebeloma sp. (38.1%), while Peziza ostracoderma (26.8%), Naucoria salicis (24.1%), and Scleroderma areolatum (16.9%) were the most abundant taxa on Q. robur seedling roots. Our data indicate a negative effect of EM on ectomycorrhizal colonisation and on species richness of ECM fungi associated with F. sylvatica and Q. robur seedlings. None of the tested products had a negative effect on seedling growth, but seedlings treated with EM were characterised by a significant higher abundance of non-vital mycorrhizae.

We describe the ectomycorrhizal (ECM) root tips and the diversity of mycorrhizal fungal species at three English oak (Quercus robur) sites (two 120 year old sites and one 60 year old site). The three oak stands in decline, located in western Poland, were characterized by a low degree of vital ECM colonization: 30.2%, 29.1% and 25.6% at Krotoszyn (K), Piaski (P) and Karczma Borowa (KB), respectively. DNA (ITS) barcoding revealed a total of 18 ECM fungal species. Based on exploration types, ectomycorrhizae were classified with respect to ecologically relevant features. The contact type was significantly correlated with C:N and C_org, while the short distance type was correlated with Ca, phosphorus (P₂O₅) and pH. The medium distance exploration type was significantly correlated with fine-grained soil particle size fractions: coarse silt (0.05–0.02 mm) and fine silt (0.02–0.002 mm), and clay ( P > KB, and were opposite to the condition of the tree crowns. A negative correlation of vital ECM root tip abundance with the crown health status of oaks was observed, whereas higher ECM diversity reflected better crown health in the oak stands studied.

Although the importance of coarse woody debris (CWD) for species diversity is recognized, the effects of coarse woody debris decay class on species composition have received little attention. We examined how the species composition of ectomycorrhizal fungi (ECM) changes with CWD decay. We describe ectomycorrhizal root tips and the diversity of mycorrhizal fungal species at three English oak (Quercus robur L.) sites. DNA barcoding revealed a total of 17 ECM fungal species. The highest degree of mycorrhizal colonization was found in CWD_advanced (27.2%) and CWD_early (27.1%). Based on exploration types, ectomycorrhizae were classified with respect to ecologically relevant soil features. The short distance type was significantly correlated with soil P₂O₅, while the contact type was correlated with soil C/N. The lowest mean content of soil C_org was found in the CWD_absent site. The difference in total soil N between sites decreased with increasing CWD decomposition, whereas total C/N increased correspondingly. In this study we confirmed that soil CWD stimulates ectomycorrhizal fungi, representing contact or short-distance exploration types of mycelium.