Abstract

Heterobasidion annosum s.s. and H. parviporum are severe pathogens of conifers causing butt rot and root rot thus reducing the economic value of timber. Here, the antifungal activity of Bacillus subtilis isolate A18 against these two Heterobasidion species was investigated. Five different culture media with different culture age were investigated to study the effect of substrate composition and culture age for metabolite production. Bacterial cultures and cell-free culture filtrates were tested for antifungal activity. Inhibition of fungal growth was analysed using the agar disc-diffusion method. MALDI-TOF and LC-HRMS analyses were used to identify the antifungal metabolites. Substrate composition and age of culture were found to be active variables with direct effect on the antifungal activity of bacterial culture extracts. High anti-fungal activity was observed when B. subtilis was cultured in PDB, SGB and LB media for four days. Mass-spectrometry analysis showed the presence of lipopeptides in culture filtrates identified as members of the surfactins, polymixins, kurstakins and fengycins. A culture filtrate containing fengycin-type lipopeptides showed the highest bioactivity against Heterobasidion species. Bacterial cultures had higher bioactivity compared to their respective cell free culture filtrates. The results of the present study suggest that B. subtilis A18 is a powerful biocontrol agent against Heterobasidion infections of tree wounds and stumps.

Keywords

Anti-fungal compounds; Inhibition; Conifers; Lipopeptides; Biocontrol; Co-culturing

Published in

Microbiological Research
2019, Volume: 223-225, pages: 129-136

SLU Authors

• Terenius, Olle

  • Department of Ecology, Swedish University of Agricultural Sciences
    
  • Uppsala University

• Broberg, Henrik

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

Associated SLU-program

SLU Plant Protection Network


UKÄ Subject classification

Microbiology
Ecology
Organic Chemistry


Publication identifier

DOI: https://doi.org/10.1016/j.micres.2019.04.006

Permanent link to this page (URI)

https://res.slu.se/id/publ/100024