Novel screening strategy reveals a potent Bacillus antagonist capable of mitigating wheat take-all disease caused by Gaeumannomyces graminis var. tritici

Take-all is a severe root disease of wheat worldwide that is caused by the soilborne fungal pathogen Gaeumannomyces graminis var. tritici (Ggt). In this study, 272 Bacillus isolates were screened for their antifungal activity invitro to Ggt. Of the 128 strains that demonstrated an antagonistic action, 24 of these exhibited at least three of the four plant growth promotion parameters (i.e. indole acetic acid and siderophore production, inorganic phosphorus solubilization and organic phosphorus solubilization) that were tested in wheat plants. The most effective strain found was Bacillus subtilis Pnf-12; its disease reduction effect reached 69%. Pnf-12 also caused a significant improvement (P < 0.05) in the root and shoot weights of wheat plants, though their root length and shoot height were similar to the noninoculated treatment (P > 0.05). The mechanism for this disease control may be linked to the production of the antifungal lipopeptides surfactin, iturin and fengycin production, all of which were detected in the cell-free supernatant of Pnf-12.