Inhibition of phytopathogens by fungal root endophytes of Norway spruce

• Root endophytes produce diverse kinds of metabolites with potential antifungal property.
• Root endophytes were able to inhibit the growth of plant pathogens in vitro.
• Inoculation with root endophyte increased Norway spruce root shoot ratio.
• Inoculation with root endophyte prevented the root rot pathogen infection in vitro.
• Root endophytes might serve as the first root protectors of young seedlings.

Fungal endophytes have been reported to inhibit growth of phytopathogenic microbes and some also are known to promote root growth. If endophytes of conifers can protect their host roots against invaders the screening of endophytes for their biocontrol abilities is relevant. The aim of this research was to screen for the potential inhibitory effects of selected Norway spruce root endophytes during interaction, in vitro, with well-known genera of phytopathogens (Heterobasidion parviporum, Phytophtora pini, Botrytis cinerea) and test the endophytes ability to protect Norway spruce seedlings against H. parviporum infection. The root endophytes and their metabolites were able to form inhibition zones in paired cultures with the pathogens. Higher numbers of unique metabolites were observed in culture extracts of Cryptosporiopsis sp. further suggesting that stronger inhibitory effect observed could be due to acquisition of more diverse metabolite pool. However, this endophyte decreased and retarded the root growth of Norway spruce seedlings. The endophyte Phialocephala sphareoides was able to inhibit all phytopathogens, promoted the root shoot ratio of Norway spruce seedlings and was able to prevent under in vitro conditions the infections of seedling roots by the pathogen H. parviporum.