Cadmium (Cd) stress is an obstacle for crop production, quality crops, and sustainable agriculture. An important role is played by the application of eco-friendly approaches to improve plant growth and stress tolerance. In the current study, a pre-sowing seed treatment with Rhizobium leguminosarum strains, isolated from the leguminous plants Phaseolus vulgaris (strain Pvu5), Vicia sylvatica (strain VSy12), Trifolium hybridium (strain Thy2), and T. pratense (strain TPr4), demonstrated different effects on wheat (Triticum aestivum L.) plant growth under normal conditions. Among all tested strains, Thy2 significantly increased seed germination, seedling length, fresh and dry biomass, and leaf chlorophyll (Chl) content. Further analysis showed that Thy2 was capable of producing indole-3-acetic acid and siderophores and fixing nitrogen. Under Cd stress, Thy2 reduced the negative effect of Cd on wheat growth and photosynthesis and had a protective effect on the antioxidant system. This was expressed in the additional accumulation of glutathione and proline and the activation of glutathione reductase. In addition, Thy2 led to a significant reduction in oxidative stress, which was evidenced by the data on the stabilization of the ascorbate content and the activity of ascorbate peroxidase. In addition, Thy2 markedly reduced Cd-induced membrane lipid peroxidation and electrolyte leakage in the plants. Thus, the findings demonstrated the ability of the R. leguminosarum strain Thy2, isolated from T. hybridium nodules, to exert a growth-promoting and anti-stress effect on wheat plants. These results suggest that the Thy2 strain may enhance wheat plant growth by mitigating Cd stress, particularly through improving photosynthesis and antioxidant capacity and reducing the severity of oxidative damage. This may provide a basic and biological approach to use the Thy2 strain as a promising, eco-friendly candidate to combat Cd stress in wheat production.

Cadmium stress is a barrier to crop production, yield, quality, and sustainable agriculture. In the current study, we investigated the characteristics of bacterial strain Pseudomonas sp. OBA 2.4.1 under cadmium (CdCl₂) stress and its influence on Cd stresses in pea (Pisum sativum L.) seedlings. It was revealed that strain OBA 2.4.1 is tolerant of up to 2 mM CdCl₂, and seed treatment with the bacterium enhanced pea plant growth (length of seedlings) under 0.5 mM cadmium stress. This bacterial strain showed plant growth-promoting properties, including biofilm formation and siderophore activity. An important advantage of the studied strain OBA 2.4.1 is its ability to colonize the plant roots. Moreover, the inoculation with strain OBA 2.4.1 significantly reduced oxidative stress markers in pea seedlings under cadmium stress. These findings suggest that cadmium stress-tolerant strain OBA 2.4.1 could enhance pea plant growth by mitigating stress-caused damage, possibly providing a baseline and eco-friendly approach to address heavy metal stress for sustainable agriculture.

Since many members of the genus Pseudomonas have growth-stimulating properties and are able to carry out biological control, they may be used to develop biopreparations and environmentally friendly fertilizers. The goal of the present work was to isolate new Pseudomonas strains from the rhizosphere of leguminous plants of the Southern Ural and to study their economically useful properties. Molecular genetic analysis of these bacterial strains was carried out. According to the results on the nucleotide sequences of the 16S rRNA and rpoD genes, four Pseudomonas strains were identified. One of them, Pseudomonas sp. OBA 2.4.1, was closest to the type strain of Pseudomonas fluorescence in terms of the homology of the studied genes, and the strains of Pseudomonas sp. OBA 2.9, GOR 4.17, and STA 3 were most closely related to the type strain of Pseudomonas koreensis. Further studies revealed that all the studied bacteria were capable of forming biofilms on both inert surfaces and plant roots and exhibited antagonistic activity against phytopathogenic fungi. Moreover, three strains were shown to dissolve inorganic phosphate. Treatment of red clover seeds with Pseudomonas sp. OBA 2.4.1 resulted in an 18% increase in seed germination and a 21% increase in dry plant biomass relative to the control. The data obtained allow us to consider the studied microorganisms as bacteria that can have a positive effect on plant growth and development.

Screening of nodule bacteria (rhizobia) forming symbiotic relationships with legumes has been performed in order to isolate strains resistant to cadmium ions in a wide range of concentrations (6–132 mg/kg). The effect of cadmium salts (6, 12, 24 mg/kg) on the legume-rhizobium symbiosis of the pea Pisum sativum L. with Rhizobium leguminosarum and of the fodder galega Galega orientalis Lam. with Rhizobium galegae has been studied under experimental laboratory conditions. No statistically significant differences have been revealed in the growth and biomass of plants with regard to the control in the range of concentrations given above. However, it was found that cadmium inhibited nodulation in P. sativum and stimulated it in G. orientalis.

Three bacteria strains of Pseudomonas sp. resistant to heavy metals were isolated from chemically contaminated soil. An analysis of the nucleotide sequences of the 16S rRNA and rpoD genes identified the Pseudomonas sp. 17 НМ strain as Pseudomonas capeferrum, and the strains of Pseudomonas sp. 65 НМ and 67 НМ were most closely related to the type strains of Pseudomonas silesiensis and Pseudomonas umsongensis, respectively. It was shown that the strains of Pseudomonas sp. 17 НМ, 65 НМ, and 67 НМ were characterized by different levels of resistance to heavy metals, with the maximum tolerable concentration (MTC) of zinc being 1 mМ for all strains, that of cadmium, 1, 1.5, and 1 mМ; of lead, 5, 5, and 4 mМ; and of nickel, 7, 9, and 7 mМ, respectively. All Pseudomonas strains can form biofilms and have the properties of PGPR bacteria. Treatment of alfalfa seeds (Medicago sativa L.) with the strains of Pseudomonas sp. 17 НМ, 65 НМ, and 67 НМ under cadmium stress increased the dry weight of alfalfa seedlings up to 40% and the content of chlorophyll a and b in the leaves by 25–33% relative to the control.

The carbohydrate-binding sequences of the lectin genes from spring vetchling Lathyrus vernus (L.) Bernh., marsh vetchling L. palustris (L.), and Gmelin’s vetchling L. gmelinii (Fitsch) (Fabaceae) were determined. Computer-aided analysis revealed substantial differences between nucleotide and predicted amino acid sequences of the lectin gene regions examined in each of the three vetchling species tested. In the phylogenetic trees based on sequence similarity of carbohydrate-biding regions of legume lectins, the sequences examined formed a compact cluster with the lectin genes of the plants belonging to the tribe Fabeae. In each plant, L. vernus, L. palustris, and L. gmelinii, three different lectin-encoding genes were detected. Most of the substitutions were identified within the gene sequence responsible for coding the carbohydrate-binding protein regions. This finding may explain different affinity of these lectins to different carbohydrates, and as a consequence, can affect the plant host specificity upon development of symbiosis with rhizobium bacteria.