Postharvest diseases of potato lead to significant food and economic losses worldwide. The exogenous application of eco-friendly methods plays an important role in the control of postharvest decay. In this work the effects of endophytic bacteria B. subtilis (10-4, 26D) were studied in the context of two application parameters: concentration, with a range between 10³–10⁸ CFU/mL tested, and synergistic effects of the signal molecule salicylic acid (SA) (0.05 mM) on potato tubers’ resistance to Phytophthora infestans and Fusarium oxysporum during storage. The experiments were carried out on hydroponically grown potato (Solanum tuberosum L.) mini-tubers. This study demonstrates the suppressive effect of B. subtilis (10-4, 26D) on diseases of potato during storage and reveals that this effect happens in a dose-dependent manner, both individually and in combination with SA. The most effective concentrations of B. subtilis for suppression of both Ph. infestans and F. oxysporum are 10⁸ CFU/mL (10-4 and 26D), 10⁷ CFU/mL (10-4 + SA) and 10⁶ CFU/mL (26D + SA). The ability of B. subtilis (10-4, 26D) to effectively penetrate and colonize the internal tubers’ tissues when applied immediately prior to storage, and the ability of SA to accelerate these processes, have been proven. B. subtilis (10-4, 26D), individually and in compositions with SA, increased ascorbic acid content and decreased pathogen-induced proline accumulation and lipid peroxidation in tubers. This indicates a protective effect conferred to cells against reactive oxygen and an extension of aging processes, manifested by a prolonged shelf life and extended preservation of fresh appearance.

In nature, plants are constantly exposed to a varied abiotic and biotic stresses or their combinations, limiting the productivity of major crops, including wheat. Combinations of drought and soil-borne Fusarium-instigated diseases are the most common combinations of stresses, significantly reducing wheat yield around the world. Here, were analyzed the potential of application of endophytic bacteria Bacillus subtilis (strain 10–4) together with the natural signal molecule salicylic acid (SA) to improve growth and tolerance of Triticum aestivum L. (wheat) plants under combined drought and Fusarium culmorum-instigated root rot (FRR) stresses. It was revealed that pre-sowing treatment with B. subtilis 10–4, SA, and B. subtilis 10–4 + SA, both under normal and combined drought conditions, notably reduced (by 50–80% or more) the incidence of FRR development in wheat plants, with the most notable effect for B. subtilis 10–4 + SA (wherein disease symptoms were almost absent). Moreover, B. subtilis 10–4, SA, and especially B. subtilis 10–4 + SA increased plant growth (root and shoot length, fresh and dry biomass) under normal (up to 20–50%), drought (up to 15–40%), FRR (up to 15–30%), and combined drought + FRR stresses (up to 20%), with the maximum effect for B. subtilis 10–4 + SA. Additionally, B. subtilis 10–4, SA, and B. subtilis 10–4 + SA decreased stress (drought, FRR, and combined drought + FRR)-instigated lipid peroxidation and osmotic damages of plant cells. The findings indicate that endophytic bacteria B. subtilis 10–4 alone and in a mixture with SA may be used as an effective eco-friendly agent to improve wheat growth and tolerance under the influence of drought, FRR, and combinations of these stresses.

Heavy metal ions, in particular cadmium (Cd), have a negative impact on the growth and productivity of major crops, including wheat. The use of environmentally friendly approaches, in particular, bacteria that have a growth-stimulating and protective effect, can increase the resistance of plants. The effects of the pre-sowing seed treatment with the plant growth-promoting endophyte Bacillus subtilis 10-4 (BS) on cadmium acetate (Cd)-stressed Triticum aestivum L. (wheat) growth, photosynthetic pigments, oxidative stress parameters, roots’ lignin content, and Cd ions accumulation in plants were analyzed. The results showed that the tested Cd-tolerant BS improved the ability of wheat seeds to germinate in the presence of different Cd concentrations (0, 0.1, 0.5, and 1 mM). In addition, the bacterial treatment significantly decreased the damaging effects of Cd stress (1 mM) on seedlings’ linear dimensions (lengths of roots and shoots), biomass, as well as on the integrity and permeability of the cell walls (i.e., lipid peroxidation and electrolyte leakage) and resulted in reduced H₂O₂ generation. The pretreatment with BS prevented the Cd-induced degradation of the leaf photosynthetic pigments chlorophyll (Chl) a, Chl b, and carotenoids. Moreover, the bacterial treatment intensified the lignin deposition in the roots under normal and, especially, Cd stress conditions, thereby enhancing the barrier properties of the cell wall. This manifested in a reduced Cd ions accumulation in the roots and in the restriction of its translocation to the aboveground parts (shoots) of the bacterized plants under Cd stress in comparison with non-bacterized controls. Thus, the pre-sowing seed treatment with the endophyte BS may serve as an eco-friendly approach to improve wheat production in Cd-contaminated areas.

BACKGROUND: The beginning of the life cycle of a leguminous plant in its natural habitat is usually associated with interaction with nodule bacteria in order to form a nitrogen-fixing symbiosis. In a short period of time, a plant needs to “choose” suitable microsymbionts for itself. Since a wide variety of rhizobial strains is formed in the rhizosphere of legumes, the choice made by the macrosymbiont will further influence its productivity. AIM: The purpose of our work was to compare the principles of selection by different plants of their microsymbionts at different stages of plant development. MATERIALS AND METHODS: Nodule bacteria Trifolium hybridum L. and Galegaorientalis Lam. were taken into the study. Their genetic diversity was studied by the RAPD method, a phylogenetic analysis of bacteria and their symbiotic nodC and nifH genes was carried out, and their nitrogen-fixing activity was assessed. RESULTS: It was found that the rhizobia that form nodules on the roots of the studied leguminous plants at different stages of their vegetation have certain patterns. It was found that the highest polymorphism and specific nitrogen-fixing activity are characteristic of bacteria obtained from nodules formed at the initial stage of vegetation. CONCLUSIONS: We assume that the plasticity of the rhizobia genome gives the host plant the ability to more flexibly adjust its nitrogen-fixing apparatus to changes in growing conditions.