Putative biocontrol agents for European forest pathogens found in English oak (Quercus robur L.) endosphere

In Europe, pathogens such as Heterobasidion annosum , Hymenoscyphus fraxineus , Lophodermium seditiosum , and Phellinus tremulae cause extensive tree loss. Microorganisms used as biocontrol agents (BCAs) can be an eco-friendly alternative to chemical fungicides and thus help control pathogen growth and spread in a sustainable manner. Six fungi: Byssochlamys spectabilis , Talaromyces amestolkiae , Aspergillus salwaensis , Neocucurbitaria quercina , Meyerozyma guilliermondii , and Microstroma bacarum , were isolated from pedunculate English oak ( Quercus robur L.), and together with bacteria Bacillus aryabhattai , Pseudomonas azotoformans , and Pseudomonas paralactis , as well as two strains of Pantoea agglomerans were tested in dual culture assays for their antagonism against these pathogens. Additionally, their abilities to produce indole-3-acetic acid (IAA), siderophores, solubilise potassium, organic and inorganic phosphates were determined. All the isolates produced IAA and solubilised phosphates. Only T. amestolkiae solubilised potassium, but this fungus and M. guilliermondii could not produce siderophores. M. guilliermondii , Pseudomonas spp., and Pantoea spp. expressed broad-spectrum antagonism. P. azotoformans showed the highest inhibition of P. tremulae (57.5%) and L. seditiosum (68.4%), B. spectabilis of H. fraxineus (59.8%), and M. guilliermondii of H. annosum (45.7%). Overall, these results will facilitate extensive BCA research for these forest pathogens and the potential BCA commercialisation and will promote sustainable forestry practices.