Investigation of the Biocontrol Potential of Two Ash Endophytes against Hymenoscyphus fraxineus Using In Vitro Plant–Fungus Dual Cultures

Abstract

Development of effective biocontrol procedures using ash endophytes to combat an ash pathogen Hymenoscyphus fraxineus would be an appropriate contribution to the ongoing effort to protect European ash stands against ash decline. In this study we investigated the biocontrol potential of two ash endophytes, Thielavia basicola and Minimidochium sp., against H. fraxineus using in vitro plant-fungus and fungus-fungus dual cultures approach in three biocontrol models. The tests aimed to determine whether the endophytes show antagonism toward Fraxinus excelsior and F. pennsylvanica, to assess the level of antagonism of the endophytes toward H. fraxineus and to identify potential secondary metabolites induced by the presence of H. fraxineus. The results that dual culture experiments modeled according to our design may be a very useful tool to precisely study biocontrol potential of fungi, i.e., without the impact of environmental factors. Such experiments also enable the selection of most resistant ash genotypes and rapid propagation, producing large numbers of pathogen-free seedlings. It should be noted, however, that both of the endophytes tested in the dual cultures strongly inhibited the growth of H. fraxineus. Their growth under the influence of callus/seedlings was also inhibited. Comparison of HPLC profiles showed that the presence of H. fraxineus in the post-culture medium induced the production of an unknown secondary metabolite in this species. Such results suggest that some of the plant–fungus combinations examined in this study may have potential to be developed as biocontrol methods, thus increasing the survivability of ash stands under natural conditions.

The efficiency of Thymus vulgaris, Lavandula angustifolia, and Cupressus sempervirens essential oils in suppression of Hymenoscyphus fraxineus on Fraxinus angustifolia seedlings

“…Until now, biological protection measures have primarily focused on the identification and testing of various antagonistic microorganisms, primarily endophytic or saprophytic fungi in the tissues of ash trees ( Fraxinus spp. ), and their potential against H. fraxineus (Bakys et al., 2022; Becker et al., 2020; Bilański & Kowalski, 2022; Haňačková, Havrdová, et al., 2017; Kowalski & Bilański, 2021, 2022; Nawrot‐Chorabik et al., 2021; Schlegel et al., 2016). An antagonism study in planta showed that the practical application of endophytic fungi reduced necrotic lesions on trees (Barta et al., 2022).…”

Cryopreservation of Abies alba × A. numidica and Pinus nigra embryogenic tissues by stepwise dehydration method

“…Thanks to cryopreservation, the morphogenetic potential and features of given cell lines are preserved, including the ability to produce specific secondary metabolites [ 8 ]. It is also possible to select genotypes resistant to biotic factors [ 9 , 10 ]. Cryopreservation has also been used to eliminate viruses [ 11 ].…”

Bioactive Compounds from an Endophytic Pezicula sp. Showing Antagonistic Effects against the Ash Dieback Pathogen

“…These research groups tested their isolates in co-culture with H. fraxineus, identifying multiple inhibitory isolates which could potentially be developed into biocontrol agents. Nawrot-Chorabik et al [7] went one step further in that they also tested two endophytes, Thielavia basicola and Minimidochium sp., in in vitro plant-fungus systems (callus cultures and callus-regenerated seedlings). When these in vitro systems were inoculated with H. fraxineus, they only remained healthy and showed no defense responses when in co-culture with endophytes.…”