Bacteria of Bacillus genus as efficient and safe plant protection agent against pathogenic microorganisms

The study aimed to establish correlation between antagonistic activity of Bacillus strains and their effect on plant growth and soil microbial balance. Experiment was based on combination of microbiological, physiological and statistical methods, including agar well method for determining antagonism, serial dilution method for counting colonies, triphenyl tetrazolium chloride method for assessing dehydrogenase activity, and analysis of variance (ANOVA) for result reliability verification. Experiment determined that B. subtilis has a higher inhibitory capacity than B. amyloliquefaciens, determining that average diameters of inhibition were 10-15% larger, while growth inhibition index was larger by 5-8%. Lesion index in Fusarium oxysporum dropped by 33.0 percentage points (p.p.) (from 53.8% to 20.8%), in Alternaria solani by 29.0 p.p., and in Pseudomonas syringae by 27.1 p.p. Proportion of healthy plants in control group improved from 51.5-56.3% to 86.2-87.3% with B. subtilis and 82.4-84.1% with B. amyloliquefaciens. Height, number of leaves and root mass improved by 20-40% compared to control, exceeding efficiency of biological standard by 5-10%, therefore demonstrating stimulative effect of biological products on plant growth. Experiment detected no phytotoxicity or soil degradation. Biological preparations ensured stable saprophyte (1.8 × 10⁶ CFU/g), actinomycetes (1.9 × 10⁶ CFU/g) and fungi (1.8 × 10⁵ CFU/g) count, while dehydrogenase activity reached 103% compared to control. Results of experiment confirmed that Bacillus subtilis and Bacillus amyloliquefaciens are efficient antagonists of phytopathogens and safe biostimulants that can improve productivity and stabilise soil microbiocenosis. They are an efficient, environmentally sustainable alternative to chemical fungicides in sustainable farming systems