To increase the organic potato yield, it is necessary to provide the crop with sufficient nutrients and effective means of biocontrol the diseases. The research goal was to characterize the biorationals’ efficacy to achieve competitive organic potatoes’ yield under various weather conditions. A 4-year trial was carried out in the Leningrad region using Udacha variety potatoes. The tests used liquid forms of new polyfunctional biologicals Kartofin based on highly active Bacillus subtilis I-5-12/23 and organic fertilizer BIAGUM obtained from poultry manure by aerobic fermentation in a closed biofermenter. Significant stimulation in plant growth and development to the flowering phase regardless of the hydrothermal conditions of the growing season was noted. The stimulating effect was determined by the combined use of biorationals pro rata to BIAGUM dose. Kartofin biologicals and BIAGUM almost doubled the potato tubers’ yield compared to the control, regardless of the growing season conditions. At the flowering phase, the biological efficacy in potato fungal diseases incidence and development was near 90% under optimal and 50–75% under drought hydrothermal conditions. At the end of vegetation, the efficiency in fungal diseases incidence and development made up 45–65% under optimal and 45–70% under dry conditions. BIAGUM effectiveness in reducing disease development reached 45–50% regardless of growing season conditions.

The aim of this work was to study the effect of Bacillus subtilis strains VKM B-2604D and VKM B-2605D, which form the basis of the Vitaplan biological product, and their combinations with chitosan salicylate on antioxidant defense enzymes in the process of formation of resistance of wheat plants to infection with the dark brown blotch pathogen Bipolaris sorokiniana. In wheat plants treated with B. subtilis strains and their combinations with chitosan salicylate, upon subsequent infection, catalase and peroxidase are activated, which regulate the intensity of oxidative stress induced by the introduction of the pathogen. Taking the data we obtained into account, it can be assumed that the increase in plant resistance to the pathogen is realized through the control of the activity of antioxidant enzymes (in particular, catalase and peroxidase), which maintain the concentration of H₂O₂ at the level necessary for the neutralization of the phytopathogen in tissues, including the direct destruction of the invading pathogen and/or activation of crosslinking and lignification of the cell wall. These processes strengthen the cell wall and help contain the spread of the pathogen in the plant. At the same time, protective reactions are also switched on, leading to the development of induced resistance in wheat plants to dark brown spotting, which manifests itself in a decrease in the development of the disease by 25–45% relative to the infected control in the treated plants. The results indicate that the combination of active strains of microorganisms-antagonists of plant pathogens and chitosan salicylate is promising for increasing the biological efficiency and expanding the spectrum of action of the developed biological products.

Bacillus strains have long been widely and successfully used as the polyfunctional biologics’ basis in various systems for crops cultivation and protection. The research goal was to evaluate application effect from experimental prototypes of multirecycled polyfunctional biologics based on Bacillus subtilis I-5/12–23 together with compost in potato organic farming. A significant stimulation of potato plants Udacha variety growth and development up to the flowering phase was observed regardless of the growing season hydrothermal conditions. The stimulation was by the additive effect of joint biologics and compost use in proportion to its dose. The multirecycled substrate-associated and liquid polyfunctional biologics prototypes together with compost almost doubled the potato tubers biological yield compared to the control regardless the growing season conditions. In the flowering phase, the biological efficacy with respect to the potato fungal diseases incidence and development was 90% under optimal hydrothermal conditions and up to 75% under drought conditions. At the vegetation end the efficacy in the potato fungal diseases development reached 70% (compost efficiency itself more than 45%) regardless of the vegetation period conditions. Four-year scientific and producing approbation of the technological application rules for the biologics’ prototypes based on B. subtilis I5-12/23 and compost developed for the North-West region’s various weather and climatic conditions showed their high efficacy in protection the organic potato. Disease incidence on plants decreased about 80%, on tubers about 50%, their quality improved, and the marketable products yield increase at 9 t ha^− 1 (3 t ha^− 1, on average). The application’s technological rules optimizing for various weather and climatic conditions is carried out by changing the consumption norms of protection means in proportion to the limiting factors. Multirecycled polyfunctional biologics prototypes combining the properties of biopesticides, biofertilizers and inoculants can be used to ensure stable organic potato production.

The challenges of increasing crop productivity and improving harvest quality can be addressed by optimizing the phytosanitary status of agroecosystems and the application of effective and environmentally safe plant protection agents. This study investigated the effects of multifunctional biological preparations based on strains of antagonistic microorganisms of different taxonomic positions and their combinations with chitosan salicylate in the cultivation of spring soft wheat (Triticum aestivum L.). It was found that the application of multifunctional complexes based on strains of Bacillus subtilis, Streptomyces felleus S-8, Streptomyces sp. VIZR-18, and 0.1% chitosan salicylate significantly increased wheat productivity and yield (up to 147.8%) by increasing the number and length of primary and nodal roots, productive tillering, the number of spikelets, and the grain weight per spike. A significant reduction in plant disease incidence was observed: the biological efficacy against root rot was 50%, against Septoria leaf blotch 77.6%, and powdery mildew development was also significantly suppressed.

A comprehensive comparative evaluation was performed to assess the effectiveness of various methods for the combined application of chitin, chitosan, and strains of the genus Bacillus for plant disease protection. The application of chitin and chitosan to soil—both individually and in combination with the B. subtilis VKM B-2604D strain—demonstrated significant efficacy in reducing the incidence of Fusarium wilt in tomato and cucumber plants. The most pronounced protective effect, characterized by a 2–3-fold reduction in disease incidence, was observed when these components were applied together. Application of a B. subtilis VKM B-2604D + chitin/chitosan formulation achieved a 1.7-fold reduction in the incidence of gray rot in tomato (cv. Kupets), whereas the B. subtilis VKM B-2604D strain alone reduced it by only 1.4-fold. Introducing colloidal chitin into the nutrient medium for the large-scale submerged cultivation of B. subtilis strains significantly enhanced their antagonistic activity against Alternaria solani and Clavibacter michiganensis. A formulation comprising B. subtilis VKM B-2604D and VKM B-2605D with colloidal chitin exhibited a higher fungistatic effect against Cochliobolus sativus compared to the original strain. Foliar application of B. subtilis VKM B-2604D and VKM B-2605D + colloidal chitin formulation increased wheat resistance to dark brown spot and brown rust by 1.5–2.0 times compared to the original strains. The hydrolysis of colloidal chitin by bacterial chitinases yields chitooligosaccharides, which serve as effective elicitors of induced plant resistance. These compounds activate genes encoding protective proteins, including plant chitinase, and enhance the generation of reactive oxygen species, primarily H₂O₂. Hydrogen peroxide, in turn, functions as a signaling molecule, activating protein genes through redox control of transcription factors or via interaction with other signaling components. This study demonstrates that formulations based on chitin, chitosan, and selected active strains of endophytic antagonistic bacteria hold considerable promise for developing novel biopreparations with enhanced biological efficacy that strengthen plants’ natural defense responses.