Tetiana Nyzhnyk

Wheat streak mosaic virus (WSMV) is a serious viral pathogen of wheat and a major threat to global food security. Infection of susceptible plants triggers oxidative stress and disrupts physiological and biochemical homeostasis, resulting in substantial yield losses. Since chemical control of viral diseases is ineffective, biologically based resistance inducers represent a promising alternative for sustainable crop protection. This study evaluates the effectiveness of a liposomal bionanocomposite (BNC) based on a glycan–rhamnolipid complex as a seed treatment for enhancing the resistance of wheat ( Triticum aestivum L.) to WSMV through modulation of antioxidant defenses and physiological responses. Wheat plants (cv. Zymoyarka) grown from BNC-treated seeds were assessed under mock- and virus-inoculated conditions. Analyses included viral titer dynamics (DAS-ELISA), indicators of redox homeostasis (H ₂ O ₂ , MDA), activities of antioxidant and stress-related enzymes (SOD, CAT, PAL), ethylene emission, chlorophyll content, and gas exchange parameters. Pre-sowing seed treatment with BNC resulted in a moderate reduction of WSMV accumulation, which was statistically significant at 14 days post-inoculation (16.02%). BNC treatment also mitigated oxidative stress by lowering MDA levels and modulating H ₂ O ₂ dynamics compared to infected untreated plants. In virus-infected plants, it enhanced SOD and PAL activities, stabilized CAT responses, reduced ethylene overproduction, and partially restored chlorophyll content and photosynthetic performance. These results indicate that BNC-induced activation of antioxidant and stress-protective mechanisms improves the physiological resilience of wheat during WSMV infection and supports the potential of this biotechnological approach as a component of integrated crop protection against viral diseases. Key points: • BNC stimulates antioxidant enzymes and modulates wheat redox homeostasis. • Eco-friendly BNC offers a sustainable strategy for managing viral diseases. • BNC induces systemic, pre-adaptive metabolic adjustments.

Background: The use of exogenous compounds with growth-regulatory properties can play an effective part in providing plants with the necessary plastic resources for the synthesis of protective compounds. The aim of the research is to determine the effectiveness of salicylic acid and methyl jasmonate treatment for inducing resistance in soybean-Bradyrhizobium symbiosis, and improving symbiotic capacity. Methods: Soybean nodule bacteria Bradyrhizobium japonicum cultures were treated with salicylic acid (50 µM) or methyl jasmonate (0.75 µM) and used to create symbioses with soybean. The symbioses were cultivated under normal watering and water stress conditions, and the resulting plants were tested for inter alia pro-oxidant-antioxidant status, productivity and N-fixation activity. Results: The 0.75 µM methyl jasmonate treatment demonstrated 54.7% catalase and 14.6% greater superoxide dismutase (by 14.6%) activity, as well as and induced two-fold higher hydrogen peroxide, under water stress; in addition, nodulation processes were stimulated by 40% and inhibited nitrogen-fixing activity inhibited by 73.5%. The 50 µM salicylic acid treatment exhibited 54.5% lowered hydrogen peroxide, but 20.7% greater superoxide dismutase activity and 44.8% higher catalase activation water stress; this increased the efficiency of molecular nitrogen fixation (by 23.5%) and productivity (by 15.9%) in soybeans. Conclusions: Effect of 50 µM SA-treated Bradyrhizobium effectively activates the protective antioxidant mechanisms of soybean, improving symbiotic capacity and stress tolerance. Methyl jasmonate 0.75 µM in combination with Bradyrhizobium stimulates nodulation and inhibites nitrogen fixation in soybean under both optimal and insufficient water supply.

Background: The tolerance and productivity of soybeans under the current climate change conditions can be increased by providing these crops with the necessary macro- and microelements. This can be achieved using effective Bradyrhizobium strains for seed inoculation and adding chelated trace elements. Methods: Soybean Bradyrhizobium japonicum symbioses were cultivated by adding chelates of trace elements, such as iron (Fe), germanium (Ge), and molybdenum (Mo), to the culture medium, after which microbiological and biochemical analyses were performed. Results: The addition of chelated forms of Fe or Ge to the Bradyrhizobium culture medium promoted a change in the pro-oxidant-antioxidant balance in soybean nodules under different water supply conditions. This is due to the production of hydrogen peroxide in the nodules (an increase of 12.9%), as well as a twofold increase in the ascorbate peroxidase activity and a decrease in the levels of superoxide dismutase (by 40%) and catalase (by 50%) under water stress. Stimulation of nodulation and nitrogen fixation in soybeans (by 40.1 and 73.0%) and an increase in grain productivity (by 47.5 and 58%) were observed when using Bradyrhizobium inoculant containing Fe or Ge chelates. The inoculation of soybeans with Bradyrhizobium modified using Mo chelate causes similar changes in antioxidant processes as Fe or Ge chelates, but the soybean symbiotic capacity decreases under water stress. Conclusion: Chelated forms of Fe or Ge as additional components in the Bradyrhizobium culture medium are effective in regulating the antioxidant status of soybeans under drought conditions and can simultaneously contribute to increased nitrogen fixation and grain productivity. These findings are important in expanding the current technologies used to grow this legume in risky farming areas caused by climate change.

Growth regulators play an important role in activating the main signal transduction pathways in response to stress, and their activity is key in the general mechanism to understanding the formation of phytoimmunity under biotic stress. The study investigates the specificity of stress-protective reactions in winter wheat varieties with varying degrees of sensitivity to the phytopathogen Blumeria graminis (DC) Speer f. sp. tritici, and determined the effectiveness of exogenous salicylic and succinic acids as inducers of resistance to powdery mildew. Exogenous application of 0.1 mM salicylic acid induced stress-protective reactions in the resistant wheat, characterised by increased ethylene release, and phenylalanine amino-lyase and ascorbate peroxidase activity in the flag leaves. These steps help optimize its physiological state and productivity by preserving the integrity of cell membranes and its chlorophyll content. Exogenous succinic acid at a concentration of 0.1 mM also led to the activation of protective antioxidant systems, which did not have a positive effect on plant physiology or productivity during infection. The susceptible variety of winter wheat was unable to mobilize the necessary stress-protective systems, regardless of salicylic or succinic acid treatment, resulting in the spread of infection and reduced productivity. The resistance of winter wheat to phytopathogen damage (Blumeria graminis (DC) Speer f. sp. tritici) is determined by the capacity of the plant to mobilize stress-protective reactions and optimize its metabolism. Salicylic acid (0.1 mM) effectively enhances plant defence systems, thus improving plant physiology and productivity during the spread of powdery mildew.

The full text of this preprint has been withdrawn, as it was submitted in error. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.

The full text of this preprint has been withdrawn, as it was submitted in error. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.

Background: Rhizobial inoculation in combination with fungicidal seed treatment is an effective solution for improving soybean resistance to modern climate changes due to the maximum implementation of the plant’s stress-protective antioxidant properties and their nitrogen-fixing potential, which will contribute to the preservation of the environment. Methods: Model ecosystems at different stages of legume–rhizobial symbiosis formation, created by treatment before sowing soybean seeds with a fungicide (fludioxonil, 25 g/L) and inoculation with an active strain of Bradyrhizobium japonicum (titer 109 cells per mL), were subjected to microbiological, biochemical, and physiological testing methods in controlled and field conditions. Results: Seed treatment with fungicide and rhizobia showed different patterns in the dynamics of key antioxidant enzymes in soybean nodules under drought conditions. Superoxide dismutase activity increased by 32.7% under moderate stress, while catalase increased by 90.6% under long-term stress. An increase in the antioxidant enzyme activity induced the regulation of lipoperoxidation processes during drought and after the restoration of irrigation. Regeneration after stress was evident in soybean plants with a combination of fungicide seed treatment and rhizobial inoculant, where enzyme levels and lipoperoxidation processes returned to control plant levels. Applying seed treatment with fungicide and Rhizobium led to the preservation of the symbiotic apparatus functioning in drought conditions. As proof of this, molecular nitrogen fixation by nodules has a higher efficiency of 25.6% compared to soybeans without fungicide treatment. In the field, fungicidal treatment of seeds in a complex with rhizobia inoculant induced prolongation of the symbiotic apparatus functioning in the reproductive period of soybean ontogenesis. This positively affected the nitrogen-fixing activity of soybeans during the pod formation stage by more than 71.7%, as well as increasing soybean yield by 12.7% in the field. Conclusions: The application of Rhizobium inoculant and fungicide to seeds contributed to the development of antioxidant protection of soybean plants during droughts due to the activation of key enzymatic complexes and regulation of lipoperoxidation processes, which have a positive effect on nitrogen fixation and productivity of soybeans. This is a necessary element in soybean agrotechnologies to improve plant adaptation and resilience in the context of modern climate change.

The development of new nanotechnological approaches and the appearance of preparations with low concentrations of microelements can serve as a basis for promising solutions aimed at increasing stress-protective properties and tolerance to the adverse factors effects. The aim of the study is to show the effectiveness of seed inoculation with nodule bacteria modified by chelate forms of trace elements germanium, ferrum and molybdenum to stimulate antioxidant properties and improve the functioning of the Glycine max (L.) Merr. – Bradyrhizobium symbiosis in insufficient water supply conditions. For this, the symbiotic systems of soybean with active virulent Bradyrhizobium japonicum B1-20 were used with the addition of chelated forms of ferrum, germanium and molybdenum in a dilution of 1:1000 to the culture medium. The chelator was citric acid. At the phenological stages during active nitrogen fixation by soybeans, two models of plant watering regimes were created ̶ optimal at the level of 60% of the full field capacity and insufficient/water stress at the level of 30% of the full field capacity. Microbiological, physiological, and biochemical methods of plant testing were used. It was found that the addition of rhizobia, chelated forms of germanium or ferrum to the culture medium, induces an increase in the antioxidant properties of plants by activating the key enzymatic complexes of superoxide dismutase and ascorbate peroxidase in soybean nodules and leaves under water stress. The use of chelated forms of ferrum or germanium led to the stimulation of the Bradyrhizobium nodulation potential, which was accompanied by the optimization of the water status and growth processes of soybean plants in insufficient moisture supply conditions. It was shown that inoculation with rhizobia containing chelated forms of molybdenum induced soybean plants sensitive to water deficit, as evidenced by an unstable reaction of enzyme activity, decrease or increase, in nodules and leaves. It inhibits nodulation processes on soybean roots and at the same time disrupts the water status of plants with insufficient water supply. It was concluded that the addition of chelated forms of germanium or ferrum to the rhizobia culture medium is a promising solution for stimulating the protective antioxidant properties of soybeans, which helps to optimize the physiological state of plants under insufficient water conditions.

The formation of legume-rhizobial symbiosis goes through a series of coordinated stages, the main of which is the distant interaction of symbionts, which i