Identification of antifungal substances secreted by Bacillus subtilis Z-14 that suppress Gaeumannomyces graminis var. tritici

ABSTRACT

Bacillus subtilis strain Z-14 has biological control activity against the take-all fungus Gaeumannomyces graminis var. tritici (Ggt). In Petri dishes, the crude extract from B. subtilis Z-14 culture filtrate reduced take-all severity in roots of wheat seedlings by 91.3% and potted plants by 69.8% compared to the Ggt-inoculated control. Treatment with the crude extract also significantly (P < .05) increased growth of roots’ average length, and fresh weight in comparison with those of the Ggt-inoculated control. B. subtilis Z-14 culture filtrate was relatively thermally stable with 88.2% of the antifungal activity being retained after being heated at 100°C for 30 min. Meanwhile, the antifungal activity remained almost unchanged (>95%) when the culture filtrate was exposed to a pH ranging from 3 to 8, but significantly reduced in basic conditions. This activity was not transferred to the organic solvent phase after treatment with organic extraction agents. B. subtilis Z-14 culture filtrate exhibited a broad spectrum of antifungal activities against various phytopathogenic fungi. Three homologs of iturin A (C14–16) were characterised by liquid chromatography-mass spectroscopy (LC-MS) and electrospray ionisation mass spectrometry/mass spectrometry collision-induced dissociation (ESI-MS/MS CID).

KEYWORDS:

• Bacillus subtilis
• Gaeumannomyces graminis var. tritici
• antifungal activity
• culture filtrate
• iturin A

Acknowledgements

We thank Professor Kejian Ding (College of plant protection, Agricultural University of Anhui, China) for kindly providing an isolate of the take-all pathogen.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a grant from the Hebei Provincial National Natural Science Foundation of China [grant number C2014204027].