An ectomycorrhizal symbiosis differently affects host susceptibility to two congeneric fungal pathogens

Abstract

Abstract The role of ectomycorrhizal fungi in modulating host susceptibility to fungal pathogens is poorly known. Pinus sylvestris susceptibility to two congeneric fungal pathogens was compared between mycorrhizal and non-mycorrhizal plants. The ectomycorrhizal fungus was Suillus luteus, while the pathogens were Heterobasidion irregulare and H.\xa0annosum. H.\xa0irregulare is native to North-America and invasive to Europe, whereas S.\xa0luteus and H.\xa0annosum are native to Eurasia. Non-mycorrhizal plants were equally susceptible to both pathogens. Mycorrhizal plants were significantly less susceptible to H.\xa0annosum than non-mycorrhizal plants, whereas there were no differences when considering H.\xa0irregulare. The abundance of ectomycorrhizas was negatively and significantly correlated to the level of host susceptibility only to H.\xa0annosum. This study shows that the protective role of ectomycorrhizal fungi may differ when the host is challenged by congeneric fungal pathogens. Results add a further clue to explain and predict the invasiveness of H.\xa0irregulare in Europe.