The factors increasing the inducing activity of two Bacillus. subtilis strains in the protection of wheat against pathogens of spot blotch Bipolaris sorokiniana and leaf rust Puccinia triticina

The purpose of this work was to evaluate the contribution of the culture liquid of Bacillus subtilis strains VKM B-2604D and VKM B-2605D and its components (cell-free supernatant and bacterial cell suspension) to the formation of induced resistance to spot blotch and leaf rust in wheat plants, as well as to establish the optimal cell concentration and application time which determine the effectiveness of the laboratory samples containing 0.1 % chitosan salicylate (CS). It is assumed that the culture liquid and its supernatant contain biologically active metabolites possessing elicitor activity and responsible for the manifestation of induced wheat resistance to spot blotch and leaf rust. Treatment of wheat leaves with culture liquid and supernatant reduced the B. sorokiniana infection level by 1.5–2 times, and P. triticina by 20 % and 10 %, respectively, as compared to the control. Meanwhile, the suspension of bacterial cells did not suppress the development of the disease symptoms. It has been experimentally shown that all culture liquid samples tested showed the greatest inducing effect at the concentration of 109 CFU/ml. It was found that among the application timing variants (1 and 2 days before and 1 and 2 days after the inoculation), pre-treatment of wheat plants one day before the pathogen inoculation was the most effective, significantly reducing the disease development. As a result, the area of leaf damage by the spot blotch and the leaf rust was decreased 6- and 10-fold, respectively, as compared to the control.