Efficacy of antagonist bacteria of the genera Bacillus and Pseudomonas against barley net blotch pathogen in laboratory conditions

Barley net blotch is an economically significant disease of global importance that leads to 10–40% yield loss. The pathogen, Pyrenophora teres, is a pathogen with a high risk of developing multiple resistance to several chemical fungicides at once. Therefore, the development of the methods of biological control of this pathogen is an urgent task. The antagonistic and protective effect of Bacillus velezensis strains BZR 336 g, BZR 517 and Pseudomonas chlororaphis BZR 245 F on two winter barley varieties with different resistance to the net blotch pathogen was investigated. It was found that the strains reduced the growth of P. teres mycelium by an average of 70%, while the pathogen mycelium had various signs of degradation at the microscopic level – deformation, twisting, "vacuolisation". Application of the strains on two varieties of barley for treatment of plants before sowing and during vegetation provided on average suppression of infection penetration into plant tissue by 38.4% and reduction of the development of already penetrated pathogen in plant tissue by 23.2%. When treating only vegetative plants, these values were lower by 3–37%. The susceptible variety Romance showed more effective suppression of infection penetration into plant tissues than suppression of infection spread in already infected plants. The opposite was true on the resistant variety Iosif. The obtained data allow us to conclude that biological methods of controlling barley net blotch have the potential of efficiency and reduce the development of P. teres. The application of biological control of plant diseases will contribute to the production of environmentally safe products in conjunction with the reduction of pesticide pressure on agrocenoses. For a more objective assessment, it is necessary to conduct field studies to evaluate the protective potential of strains on the natural infection background under changing environmental conditions. 

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