Among the different strategies of plant protection from phytopathogens, the use of beneficial fungi has been described as a sustainable, eco-friendly approach. The aim of the present work was to evaluate the antagonistic activity of beneficial fungal strains in vitro and in vivo. The studied strains (Beauveria bassiana T7, Beauveria bassiana T15, Metarhizium robertsii An1, Talaromyces pinophilus T14) had pronounced antagonistic activity against three phytopathogens (the growth inhibition was 18.2–51%). In pot experiments, the studied strains significantly reduced the level of stress in barley plants caused by phytopathogenic load. The beneficial effect of the strains consisted of an increase in the morphometric parameters of plants and a positive effect on photosynthetic pigments and proline levels. The 1-aminocyclopropane-1-carboxylate deaminase level of the strains varied from 0.95 to 2.73 µM α-KB mg protein⁻¹ h⁻¹. The most significant mechanisms of antagonistic action of the M. robertsii An1 strain were the following: the production of hydrolytic enzymes (chitinase and glucanase activity amounted to 0.23 U mL⁻¹ and 3.42 U mL⁻¹, respectively) and the synthesis of soluble volatile and non-volatile compounds with antifungal properties, including destruxin E, destruxin A, and hydroxyanthraquinones. The results obtained revealed the potential of the studied strains for their integration into a sustainable agricultural system.

Soil salinity has become a global issue that is directly related to land degradation and results in many changes in climate, ecosystem services, and biodiversity. The present study focuses on the investigation of beneficial properties of a plant probiotic bacterial strain as an eco-friendly and sustainable approach to promote crop growth in saline soil. The endophytic halotolerant strain Pseudomonas flavescens D5 isolated from common chicory (Cichorium intybus L.) was able to grow on a medium containing 15% NaCl; produced indole-3-acetic acid (45.2 μg mL⁻¹) and polyhydroxyalkanoate (1.72 g L⁻¹); and had amylolytic, cellulolytic, and proteolytic activities. Polyhydroxyalkanoate had a pronounced antifungal activity against Fusarium graminearum, F. solani, F. oxysporum, and Alternaria alternata. Under salt stress conditions, inoculation with Ps. flavescens D5 increased the shoot biomass of barley plants by 8–30%, root biomass by 7–20%, chlorophyll a by 18–52%, and chlorophyll b by 7–15%. The content of proline decreased by 1.5–1.8 times. An increase in the activity of antioxidant enzymes (catalase, guaiacol peroxidase, and ascorbate peroxidase) was determined. In inoculated plants growing in saline soil, the content of Na⁺ ions was lower by up to 54.8% compared to control. This strain is promising for stimulating plant growth and protecting them from diseases and other adverse environmental factors, including salt stress.

The aim of this study is to develop and comprehensively evaluate the efficacy of an innovative formulation of a biological preparation consisting of a bacterial consortium (Serratia proteamaculans B5, Pseudomonas putida D7 and Lysinibacillus sp. S1), embedded in a pullulan polysaccharide matrix, as an agent for inducing systemic resistance in barley (Hordeum vulgare L.) to phytopathogenic stress caused by Fusarium graminearum. To optimize the product’s protective efficacy and minimize the pesticide load on the agroecosystem, a reduced dose of Fundazol (50% of the standard rate) was incorporated into the formulation. The constituent strains exhibited high indole-3-acetic acid production (53.29–69.2 μg·mL⁻¹) and strong antagonistic activity against phytopathogenic fungi, with inhibition zones reaching up to 32.5 mm. Pot and field trials were conducted to comprehensively assess the effect of the biological product on the stress tolerance of barley plants. Pre-sowing seed treatment reduced proline accumulation (by up to 2.3-fold), maintained photosynthetic pigment levels, and increased field germination to 79%. Under infectious field conditions, treatment with the biopreparation contributed to the stabilization of yield structure parameters (treated plants exhibited increases in height and biomass of 9–21%) and the improvement of grain quality indicators. Overall, the results obtained demonstrate the potential of the developed biopreparation as a component of comprehensive protection strategies and as an inducer of plant priming mechanisms.