Efficacy of Bacillus and Pseudomonas antagonist bacteria as biocontrol agents of barley net blotch in field conditions

   Barley net blotch is a widespread disease of cereal crops worldwide, causing significant economic losses. The predominant method of controlling it remains chemical defense, which has many negative consequences. It should be noted that the causative agent of the disease, the fungus Pyrenophora teres, belongs to the class of the pathogens with a high probability of developing multiple resistance to several chemical fungicides at once. In this regard, the protective effect of Bacillus velezensis strains BZR 336 g and BZR 517, as well as Pseudomonas chlororaphis BZR 245 F on two varieties of winter barley with different resistance to the causative agent of net blotch in two-year field trials was investigated. It was found that treatment with the above strains reduced the development of net blotch on average by 26–30% in the conditions of the central zone of the Krasnodar Territory. In 2022, the strains were able to compete in efficiency with the chemical reference. It was found that the reduction of disease development was more pronounced on the susceptible variety Romance when treated with the strains, with an average of 25.7–38.8 % compared to 20.9–25.3 % on the resistant variety Iosif. It was determined that treatment with liquid strain cultures before sowing and during the growing season is more effective than other methods. In 2018, seed and plant treatment with the strains was more effective than other methods: on the variety Iosif by an average of 6–8 % and on the variety Romance by 8–24 %. In 2022, seed and plant treatments with the strains were on average 12–17 (Iosif) and 35–38 % (Romance) more effective than other methods of treatment. The biological efficacy of the strains depended on climatic factors. In favorable weather conditions, the maximum reduction of disease development was observed with the use of strain of the Pseudomonas genus, in conditions of unstable meteorological background the greatest efficiency was demonstrated by bioagents of the Bacillus genus. The results of research have shown that biological methods of controlling winter barley net blotch are quite effective and require further implementation. Biological means of plant protection in addition to suppressing the harmfulness of phytopathogens will contribute to the production of environmentally safe products in conjunction with the reduction of pesticide pressure on agrocenoses.

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