Biological control of wheat take-all disease using some biofilm-forming Bacillus subtilis strains

Wheat take-all is one of the most important soil-borne fungal diseases that causes significant annual damage to this strategic crop in the world including Iran. In this study, potential of 27 antagonistic bacterial strains of Bacillus subtilis was evaluated in the biocontrol of Gaeumannomyces graminis var. tritici, the causal agent of wheat take-all in the laboratory and greenhouse conditions. In dual culture experiment, all studied strains had inhibition zone against growth of the pathogenic fungus and they prevented fungal growth between 39.48-96.29%. In antifungal volatile metabolites production, some strains reduced fungal growth up to 87.62%, while this for some others was less than 20%. In extracellular liquids secretion at three concentrations of 5, 15 and 25%, the most effective concentration was 25%. Results of biosurfactant production and biofilm formation showed that all the studied strains produced biosurfactant and biofilm with high variation. Correlation between production of biosurfactant and biofilm in in vitro was 0.83. Eleven strains with different potential in antagonistic effects and biofilm formation were selected for the possibility of disease biocontrol in the greenhouse conditions. All strains decreased the disease between 20-100%. About 72% of the trains reduced disease more than 50% comparing to the control. Correlation of 0.71 and 0.85 was obtained between biofilm formations and biosurfactant production in the laboratory and the greenhouse in the biological control of the disease.