Secondary metabolites produced by a root-inhabiting sterile fungus antagonistic towards pathogenic fungi

A sterile red fungus (SRF) isolated from cortices of roots of both wheat (Triticum aestivum cv. Gamenya) and ryegrass (Lolium rigidum cv. Wimmera) was found to protect the hosts from phytopathogens and promote plant growth. In this work, the major secondary metabolites produced by this SRF were analysed, and their antibiotic and plant-growth-promoting activities investigated.

Two main compounds, veratryl alcohol (VA) and 4-(hydroxymethyl)-quinoline, were isolated from the culture filtrate of the fungus. In antifungal assays, VA inhibited the growth of Sclerotinia sclerotiorum and Pythium irregulare even at low amounts, while high concentrations (>100 microg per plug) of 4-(hydroxymethyl)-quinoline were needed. Both metabolites revealed weak inhibition of Rhizoctonia solani. Furthermore, both compounds showed a growth promotion activity on canola (Brassica napus) seedlings used as bioassays.

Isolation and characterization of the main secondary metabolites from culture filtrates of a root-inhabiting sterile fungus are reported. The biological assays indicate that these secondary metabolites may have a role in both plant growth regulation and antifungal activity.

This study provides a better understanding of the metabolism of a cortical fungus that may have a useful role in the biological suppression of root-infecting soil-borne plant pathogens.