The efficiency of interaction between legumes and rhizobia depends on the genotypes of both partners, which may lead to inefficient symbiosis. This study examined interactions between three pea (Pisum sativum L.) genotypes and six Rhizobium laguerreae strains classified into three genospecies (gsN, gsO, gsR) via whole-genome phylogenetic analysis. The peculiarities of interaction between each pea genotype and each strain were studied at histological and ultrastructural levels. Both normally developing symbioses and those with various disruptions in the infection process, bacterial release, differentiation of bacteria into bacteroids, and the ability of bacteroids to maintain their functional activity were identified. It was shown that cv. ‘Rondo’ was the most successful in forming symbioses with R. laguerreae strains, in turn, strain AMPS05 was the most effective on all three pea genotypes studied. Thus, the efficiency of interaction in symbioses formed between pea and R. laguerreae strains depends on the genotypes of both partners.
Exogenous cadmium (Cd) stimulates abscisic acid (ABA) accumulation in planta, enhancing Cd tolerance by maintaining growth and limiting Cd accumulation. Since rhizobacteria that metabolise ABA may compromise Cd tolerance, tomato Ailsa-Craig plants were grown in vitro with or without 80 µM CdCl2, and with or without ABA-metabolising Rhodococcus sp. P1Y and Novosphingobium sp. P6W and the Cd-tolerant, 1-aminocyclopropane-1-carboxylate (ACC) deaminase-containing Variovorax paradoxus 5 C-2 (negative control). Root colonisation of the ABA-metabolising strains was circa 50
The aim of the study is to evaluate the efficacy of Bacillus amyloliquefaciens strain in increasing the survival rate of mint microplants (Mentha longifolia and Mentha spicata) during ex vitro adaptation in a controlled environment climate chamber. The results revealed a statistically significant and species-specific effect of the biopreparation. In M. longifolia, treatment caused complex growth stimulation: shoot length increased by 57.5 %; leaf area – by 209; raw biomass – by 166.2; dry biomass – by 128.4 %. The physiological status of plants improved significantly: the content of chlorophyll a increased by 21.7 %; chlorophyll b – by 9.1, and the total carotenoid content – by 12.5 % compared to the control of untreated plants. Overall, a 9–22 % increase in chlorophyll and carotenoid content and a 39 % increase in the NDVI (to 0.57) were observed, indicating activation of the photosynthetic apparatus. In M. spicata, the response was selective: despite a similarly significant increase in wet (195.3 %) and dry (163.2 %) biomass and an increase in NDVI (22.7 %), a decrease in the concentration of key photosynthetic pigments was recorded: chlorophyll a content decreased by 7.2 %, and the sum of chlorophylls (a + b) by 6.9 % compared to the control. This indicated a different adaptation strategy, in which resources are redistributed toward enhanced vegetative growth rather than pigment synthesis. High potential for targeted use of the B. amyloliquefaciens S21 strain as a microbiological biofortification for managing valuable plant traits was identified. For M. longifolia, this strain is recommended as an effective biostimulant of photosynthetic productivity and overall growth; for M. spicata, it is used as an agronomic technique for intensifying vegetative mass accumulation. The necessity and feasibility of developing specialized, species-specific protocols for the use of microbial inoculants in modern breeding programs aimed at producing high-quality and adaptable planting material with desired economic characteristics are substantiated.
Soil microorganisms play pivotal roles in biogeochemical cycling and plant growth promotion, directly impacting crop productivity and ecosystem stability. While assessing their responses to emerging contaminants like micro/NPs is critically important, research remains challenging due to highly variable effects contingent upon (1) soil physicochemical properties and (2) plastic characteristics (type, size, morphology, concentration, and other parameters). A one-month laboratory incubation experiment using 0.55 µm polystyrene latex nanoplastics (NPs) allowed us to investigate the microbial communities in soils in the southern taiga zone (near Saint Petersburg, Russia) react to the addition of polystyrene NPs. It was found that sandy Podzols were more resistant to the addition of NPs than loamy Retisols and Fluvisols. The most responsive components of the soil microbiome were those that were initially more abundant. These include representatives of the following phyla: Pseudomonadota, Bacillota, Actinomycetota and Planctomycetota. The alpha diversity parameters of the microbial community, expressed in the number of operational taxonomic units and bio-diversity indices (Shannon and Simpson), decreased under the influence of NPs. The dynamics of alpha diversity of the microbial community were the least pronounced in Podzol soil. Beta-diversity parameters changed the most in Hortic Retisol, slightly less in Fluvisol, and not at all in Podzol. Thus, it was found that agricultural soils were most affected by NPs (in terms of microbial community dynamics) compared to the region’s two zonal soils. Studies carried out indicate that, in the future, a threshold for the harmfulness of NPs in relation to soils should be developed, taking into account the differentiation of soils as standardized objects in terms of particle size distribution.
Pea and vetch are the important legume crops used as food, forage, and green manure in agriculture. Several new rhizobial isolates were obtained from vetch Vicia sativa root nodules. For one of them, Vst36-3, the nodulation test showed various specificity in relation to plant hosts from the Fabeae tribe, such as pea and vetch. It is in contrast to typical strains of the Rhizobium leguminosarum species complex (Rlc), which formed effective nodules as in pea and vetch. Here, whole genome sequencing was performed followed by de novo genome assembly for Vst36-3 strain. As a result of de novo genome assembly, seven contigs were generated using Oxford Nanopore Technology long reads and subsequently Illumina short reads. Phylogenetic analysis allowed us to identify this strain as Rhizobium ruizarguesonis Vst36-3. Analysis of the Sym plasmid containing the nod and nif genes revealed that R. ruizarguesonis Vst36-3 has a complete suite of essential genes for the development of symbiosis. Nevertheless, this new strain forms ineffective nodules in pea. This makes Rhizobium ruizarguesonis Vst36-3 attractive for the search and investigation of new factors of host specificity in future.
