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Soybeans are a vital crop globally, significantly contributing to food security, soil fertility, and economic development. However, soil conditions can constrain their productivity, including nutrient deficiencies and acidity. This study explores the combined effects of biochar (BC) and Rhizobium inoculation (RI) on soybean growth, nodulation, and yield. The experiment was conducted over two growing seasons and employed a split-plot design with five BC application rates (0, 2, 4, 6, and 8 t ha− 1) and two RI levels (uninoculated and inoculated) across four replications. The results demonstrated that the integration of BC and RI significantly improved various growth parameters, including nodulation, biomass accumulation, pod number, and grain yield. The highest grain yield was observed at 8 t ha−1 BC with RI, yielding 3394 kg ha−1 in 2021 and 2542 kg ha−1 in 2022. This was identical to the yield attained with the 6 t ha−1 BC rate paired with RI in both years. The inoculated control treatment consistently demonstrated the lowest grain yield. Additionally, it showed a significant (p <.05) impact on the weight of one hundred seeds. The study also revealed significant and consistent relationships among soybeans' growth and yield features. In conclusion, the findings suggest that the combined application of BC and RI has a positive impact on soybean yield and its key components. HIGHLIGHTS: Bradyrhizobium inoculation of soybeans resulted in significant changes in plant growth and yield components compared to the control treatment. Rice husk BC application at different rates (2, 4, 6, and 8 t/ha) resulted in significant changes in plant growth and yield components compared to the control treatment. The combined application of BC and RI resulted in significant changes in plant growth and yield components compared to the control treatment. Plant growth parameters, including root dry weight, shoot dry weight, and nodulation showed significant improvement with RI and BC application. Significant improvement with RI and BC application was also observed in the yield components including pod yield, grain yield, 100-seed weight, and harvest index. Correlation analysis revealed significant positive correlations between grain yield and shoot dry weight, root dry weight, nodule number, and nodule dry weight, indicating that higher grain was associated with better plant growth. [ABSTRACT FROM AUTHOR]

Non-halophytic plants are highly susceptible to salt stress, but numerous studies have shown that halo-tolerant microorganisms can alleviate this stress by producing phytohormones and enhancing nutrient availability. This study aimed to identify and evaluate native microbial communities from salt-affected regions to boost black gram (Vigna mungo) resilience against salinity, while improving plant growth, nitrogen uptake, and nodulation in saline environments. Six soil samples were collected from a salt-affected region in eastern Uttar Pradesh, revealing high electrical conductivity (EC) and pH, along with low nutrient availability. A total of 72 bacterial strains were isolated from soil and 28 from black gram (Vigna mungo) root nodules, with 32 of the soil bacteria tolerating up to 10% NaCl. These bacteria were characterized through taxonomic and biochemical tests. Cross-compatibility analysis showed two rhizobia strains were highly compatible with five salt-tolerant bacteria. These strains exhibited significant plant growth-promoting traits, including phosphate, potassium, and zinc solubilization, as well as ACC deaminase, IAA, siderophore, and EPS production. Strain Paenibacillus sp. SPR11 showed the strongest overall performance. Genetic diversity was assessed using BOX-PCR and ERIC-PCR, and strains were identified through 16S rRNA gene sequencing. In a seed germination study under saline conditions (200 mM and 300 mM), co-inoculation with Bradyrhizobium yuanmingense PR3 and Paenibacillus sp. SPR11 resulted in a significant enhancement in seed germination (40%), root growth (84.45%), and shoot growth (90.15%) compared to single inoculation of B. yuanmingense PR3. Under greenhouse conditions in Leonard jars, co-inoculation with strains PR3 and SPR11 significantly enhanced shoot and root length, fresh and dry biomass, nodule count, and nodule fresh and dry weight. Chlorophyll content, nutrient uptake, and crude protein levels increased, while proline content decreased compared to single inoculation and uninoculated seeds. Our best understanding leads us to believe that this is the very first report of utilizing co-inoculation of salt-tolerant Paenibacillus sp. SPR11 and B. yuanmingense PR3, demonstrating their promising potential to alleviate salt stress and enhance growth, root architecture, nitrogen uptake, and nodule formation in black gram under nitrogen free saline conditions. [ABSTRACT FROM AUTHOR]

Water scarcity challenges in agriculture are prompting the exploration of alternative irrigation sources, including treated effluents. This study investigates the effects of irrigation with treated slaughterhouse effluent on soybean productivity and development, with and without inoculation, over two cropping cycles. Plant performance was significantly influenced by environmental factors and the interaction between effluent and inoculation. Plant height and leaf area were greater in the second cycle, with effluent enhancing growth and foliar development. Fresh and dry shoot biomass showed significant interactions among cycle, inoculation, and effluent, with higher effluent concentrations combined with inoculation being most effective in the first cycle. Foliar nitrogen concentrations were higher in the first cycle, particularly at elevated effluent doses, while foliar sodium showed a positive correlation with nitrogen and a negative correlation with magnesium. Chlorophyll indices varied across developmental stages, with maximum chlorophyll b estimated at 85.35% effluent irrigation. Soybean yield did not vary significantly with effluent dilutions, suggesting environmental factors had a greater influence. In conclusion, treated effluent irrigation represents a sustainable strategy for soybean production, optimizing water and nutrient use while reducing reliance on chemical fertilizers. [ABSTRACT FROM AUTHOR]

Lentil (Lens culinaris Medic) is the main pulse crop and usually has low production due to numerous factors and cultivation practices. A field study was designed to investigate the best trace elements (Co, Nin, and Se) for sole application or in combination as fertigation after sowing for the lentil variety (NIA Masoor-2005). Comparatively better crop growth and yield with better quality were obtained through the application of Co, Ni, and Se, at 600, 600, and 300 g ha-1, respectively. The maximum grain yield (1638 kg ha-1) was harvested from the treatment where Co, Ni, and Se were applied at 600 g ha-1, which was 15% higher than that of the control receiving no trace elements. According to economic analyses, the best performing treatment is the use of Ni and Co in full doses, as Se has high and does not have economically effective results. All three trace elements had a positive impact on lentil nodulation (up to 33%), seed protein (4.6%), and yield increase (15%) over the control receiving no trace elements. However, with the application of Co and Ni at 600 g ha-1, each was found to be the most economical and showed comparable results regarding growth, nodulation, and yield contributing parameters compared to Co, Ni, and Se, each at 600 g ha-1. It was concluded that the use of trace elements (Co, Ni, and Se), individually or in combination, is economical and has the capacity to increase the yield and nodulation of lentils. [ABSTRACT FROM AUTHOR]

Background/Objectives: The balanced regulation of innate immunity plays essential roles in rhizobial infection and the establishment and maintenance of symbiosis. The evolutionarily conserved cell death suppressor Bax inhibitor-1 plays dual roles in nodule symbiosis, providing a valuable clue in balancing immunity and symbiosis, while it remains largely unexplored in the legume Lotus japonicus. Methods/Results: In the present report, the BI-1 gene family of L. japonicus was identified and characterized. We identified 6 BI-1 genes that translate into peptides containing 240–255 amino acids with different structural characteristics and isoelectric points. We performed phylogenetic analyses and detected evolutionary conservation and divergence among BI-1 proteins from L. japonicus, Glycine max, Medicago truncatula, Arabidopsis thaliana, and Oryza sativa. Expression profiles among different roots indicated that the inoculation of MAFF303099 significantly increased the expression of most of the L. japonicus BI-1 family genes. We down-regulated the transcripts of LjBI-1a by RNA interference and observed that LjBI-1a promotes nodulation and nodule formation. Conclusions: These discoveries shed light on the functions of BI-1 genes in L. japonicus, and simultaneously emphasize the potential application of LjBI-1a in enhancing the symbiotic nitrogen fixation ability of legumes. [ABSTRACT FROM AUTHOR]

Background: Efficient capture and use of resources is critical for optimal plant growth and productivity. Both shoot and root growth are essential for resource acquisition, namely light and CO2 by the shoot and water and mineral nutrients by roots. Soybean [Glycine max (L.) Merr.], one of the most valuable crops world-wide, uses an additional strategy, symbiotic N fixation (SNF), for N acquisition. SNF relies on development of specialized root organs known as nodules, which represent a distinct C sink. The genetic diversity of C partitioning in N fixing soybean to shoots, roots, and nodules has not been previously investigated but is valuable to better understand consequences of differential C allocation and to develop genetic resources, including identification of quantitative trait loci (QTLs). Results: A diversity panel of 402 soybean genotypes was phenotyped outdoors in a deep-tube system without addition of mineral N to measure allocation of biomass to the shoot, root, and nodules, as well as to determine nodule number, mean nodule biomass, and total shoot N accumulation. Wide ranges in phenotypes were observed for each of these traits, demonstrating extensive natural diversity in C partitioning and SNF in soybean. Using a set of 35,647 single nucleotide polymorphism (SNP) markers, we identified 121 SNPs tagging 103 QTLs that include both 84 novel and 19 previously identified QTLs for the eight examined traits. A candidate gene search identified 79 promising gene models in the vicinity of these QTLs. Favorable alleles of QTLs identified here may be used in breeding programs to develop elite cultivars with altered C partitioning. Conclusions: This study provides novel insights into the diversity of biomass allocation in soybean and illustrates that the traits measured here are heritable and quantitative. QTLs identified in this study can be used in genomic prediction models as well as for further investigation of candidate genes and their roles in determining partitioning of fixed C. Enhancing our understanding of C partitioning in plants may lead to elite cultivars with optimized resource use efficiencies. [ABSTRACT FROM AUTHOR]

The excessive use of chemical fertilizers has led to soil depletion of essential minerals, causing microorganisms to be distracted and reducing the distribution of soil fauna and flora. The field experiment examined the impact of biofertilizer (Rhizobium and Phosphorus Solubilizing Bacteria) and blended fertilizer (NPKSZn) on the growth, yield, and yield-attributing characteristics of faba bean. The experiment was laid out in RCBD with eight treatments. The result revealed that the application of biofertilizer significantly (P < 0.05) affected the growth and yield characteristics of faba bean. The longest grain filling period (51.42 days), tallest plant height (148.2 cm), Maximum nodulation (79.58), number of branches (6.42), pod per plant (34.08), highest thousand seed weight (699.9 g), grain (2369 kg ha−1), and biological yield (3942 kg ha−1), and the lowest chocolate spot disease severity index (13.33%) was noticed in dual inoculation of Rhizobium and PSB along with recommended dose of NPKSZn in both growing seasons. The highest net benefit (48,174.9 Ethiopian Birr (ETB) per ha) with an acceptable maximum marginal rate of return (789.26%) was recorded in dual inoculation of seed with Rhizobium and PSB. Therefore inoculations of Rhizobium and PSB enhance the production and productivity and reduce the chocolate spot infestation level. Hence the seed must be inoculated with a dual culture of Rhizobium and PSB along with another package of practices for the crop. [ABSTRACT FROM AUTHOR]

Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plant's need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of nodulation (AON) and autoregulation of mycorrhizal symbiosis (AOM) both negatively regulate their respective processes and share multiple components—plants that make too many nodules usually have higher arbuscular mycorrhiza (AM) fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus. Medicago truncatula has two sequence homologs: Mt TML1 and Mt TML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR–Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in Mt TML1 or Mt TML2 produced two to three times the nodules of wild-type plants, whereas plants containing mutations in both genes displayed a synergistic effect, forming 20× more nodules compared to wild-type plants. Examination of expression and heterozygote effects suggests that genetic compensation may play a role in the observed synergy. Plants with mutations in both TML s only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting that these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of Mt TML1 and Mt TML2 in M. truncatula symbiosis with beneficial microbes. [ABSTRACT FROM AUTHOR]

The aim of this work was to check the effects of five Bradyrhizobium japonicum inoculants from different producers on growth, photochemical efficiency, nitrate reductase activity, amount of hydrogen peroxide, activity of catalase, non-specific peroxidase, and superoxide dismutase, seed yield, and nodulation of soybean cv. ‘Malaga’. We also evaluated expression of such nodulation genes as NIC1, NOD21, and NORKb. The following inoculants were used: Nitragina IUNG, Nitragina Biofood, Nitroflora Mycoflor, Rhizobium Bio-Gen, and HiStick®Soy. The study was carried out on plants grown in pots in an open foil tunnel or glasshouse conditions. Experimental seeds were inoculated before sowing, while the control ones were not. Physiological and biochemical analyses involved the leaves, and gene expression was investigated in the roots. The bacterial inoculants significantly affected individual parameters of chlorophyll a fluorescence. The highest photochemical efficiency was induced by Nitroflora Mycoflor, which also activated nitrate reductase to the greatest extent. Nitragina IUNG most strongly stimulated accumulation of hydrogen peroxide, facilitated formation of the greatest number of nodules, and improved seed yield per plant in comparison with the control and other inoculants. Of the studied nodulation genes, NIC1 showed the strongest expression following HiStick®Soy treatment. Nitragina Biofood and Nitragina IUNG most significantly reduced the expression of all studied genes. Expression of NOD21 and NORKb exposed to other inoculants was the same as in the control plants. High content of hydrogen peroxide can be considered a marker of the inoculant ability to increase nodulation and yield of soybean. Commercial preparations containing the same amount of B. japonicum but different carriers of bacteria show different ability to form root nodules, and their differential impact on yield is related to the intensity of nodulation and expression of the Nod genes. [ABSTRACT FROM AUTHOR]

Summary Plant immunity is suppressed in the symbiotic nodule cells, thereby facilitating rhizobial infection. Medicago truncatula NODULES WITH ACTIVATED DEFENSE1 (MtNAD1) is crucial for suppressing immunity in nodules; however, its molecular function is unclear. We explored the molecular basis of the role of MtNAD1 in suppressing innate immunity in M. truncatula nodules. Medicago truncatula mutants lacking MtATG7 produced defective nodules, sharing some similarities with the Mtnad1 mutant nodules. Furthermore, MtNAD1 interacted with several immunity‐related proteins, including BAX‐inhibitor1a (MtBI‐1a), two Lysin‐motif proteins (MtLYM1/2), Pathogenesis‐related10 (MtPR10c/d), MtMPK3/6, and two Lysin‐motif receptor kinases (MtLYK8/9). In addition, MtNAD1 and the autophagy pathway contributed to the reduction of MtBI‐1, MtPR10c/d, and MtLYM1/2 protein levels in planta. Knocking out either the MtBI‐1 or MtLYM1/2 gene in the M. truncatula nad1 mutant can partially restore the defective nodules of the nad1 mutant. Our results demonstrate that MtNAD1 associates with the autophagy pathway by interacting with MtATG8, contributing to the degradation of several immunity‐related proteins in M. truncatula nodules during rhizobial colonization and thereby supporting the development of a successful symbiosis. [ABSTRACT FROM AUTHOR]

Silicon (Si) supplementation can enhance symbiotic functions in some legumes (Fabaceae) with their nitrogen‐fixing rhizobia, such as root nodulation and nitrogen fixation. However, it is still poorly understood how Si influences legume–insect interactions. Here, we investigated how a symbiotic legume responds not only to Si supplementation but also to herbivory treatment with varying infestation levels in two events.We conducted a controlled climate chamber experiment by growing Medicago truncatula plants inoculated with rhizobia. For half of the plants, the soil was kept without Si (−Si), whereas the other half was regularly supplemented with Si (+Si). We then infested the plants with caterpillars of Spodoptera littoralis with 0, 1 or 3 larvae and 0, 1 or 1 larva in single herbivory attack and in double herbivory attack, respectively. To understand plant responses to such treatment combinations, we examined 16 functional traits.Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations were not affected in single attack plants. However, increasing levels of herbivory led to decreases in such measured traits in double attack plants. Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory, indicating contrasting resource allocation. Herbivory did not affect the content of foliar Si, which was higher in +Si than −Si plants. Si and herbivory led to reduced foliar phenolics in double attack plants, suggesting a potential trade‐off between silicification and phenolic production. Si and herbivory led to increased trichome densities in single attack plants, but patterns were less clear in double attack plants. Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants. Relative growth rates of the caterpillars, as proxy for plant resistance, decreased mainly due to herbivory treatment, when fed on single attack plants.Using a trait‐based approach, we provide novel insights to better understand the response of a legume to Si supplementation and different herbivory levels and events. We conclude that herbivory predominantly exerts much stronger effects than Si on various plant traits, pointing to a necessity to respond to herbivory by induced defence strategies. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Comprehensive assessments were conducted on eight fast growing, novel Rhizobium isolates, short listed from a preliminary selection of 68 isolates obtained from root nodules of groundnut plants grown in diverse agro-climatic regions of eastern India. Additionally, two conventional rhizobia strains, viz. IGR6 and GN2, (collected from the Nodule Research Center, BCKV), were utilized for comparative analysis. Cluster analysis, based on carbon utilization and biochemical parameters, grouped all the test isolates with an average similarity level of 73%. The ability of the isolates to utilize a wide range of carbon sources, including hexoses, pentoses, and disaccharides, confirms their fast-growing nature. Further analysis through 16S rDNA extraction and nucleotide sequencing revealed that the promising fresh isolates exhibited 95–99% similarity to known Rhizobium species in public databases. When evaluated in pot culture experiments using new alluvial soil from the Gangetic Plains in eastern India, the native fresh isolate NRA1(PP355674) outperformed other isolates and conventional strains in terms of nodulation efficiency, plant dry matter production, and plant nitrogen uptake. This study highlights the significant potential of native Rhizobium isolates to surpass conventionally used strains in biological nitrogen fixation, supporting the development of sustainable, environmentally-friendly, and cost-effective agricultural practices. [ABSTRACT FROM AUTHOR]

Genetic variability in bacterial populations that nodulate Lupinus cosentinii in Tunisia was investigated. Phylogenetic studies of 40 isolates using recA partial sequences categorized them into three clusters within the Bradyrhizobium genus. Twenty-three strains selected from the three clusters were thoroughly examined through housekeeping genes (recA, glnII and rpoB) multilocus sequence analysis (MLSA). Our results showed that 23 representative strains were distributed in five distinct clusters, with 13 strains belonging to Bradyrhizobium canariense BTA-1T/Bradyrhizobium lupini USDA3051T (10 strains) and Bradyrhizobium hipponense aSej3T (three strains) lineages. Interestingly, eight strains occupied a separate position and could belong to two putative novel Bradyrhizobium species. The nodC phylogeny placed the 23 strains within three symbiovars: genistearum (19 strains), lupini (two strains) and, for the first time, the symbiovar cyanophyllae (two strains). Based on the worldwide phylogeography of rhizobial symbionts nodulating lupine (14 species), our results reported that eight species occurred in more than one continent, and six species were specific for one continent, e.g., Bradyrhizobium rifense, Bradyrhizobium diazoefficiens, Phyllobacterium sp. and Devosia sp. were specific to the African continent, the Bradyrhizobium iriomotense/Bradyrhizobium stylosanthis group to America, and Bradyrhizobium valentinum to the European continent. [ABSTRACT FROM AUTHOR]

Prolonged inoculation of soya bean (Glycine max L.) farms with exotic strains of Bradyrhizobium species starting in the 1960s resulted in the establishment of populations of Bradyrhizobium strains in the soils of several soya bean farms in South Africa. With the increasing number of new soya bean genotypes in the country, it is challenging to determine which genotypes are highly compatible with a given rhizobium strain. In this study, we investigated the symbiotic compatibility of native rhizobial isolates and the strains from the South African Rhizobium Culture Collection (SARCC) on ten selected locally available soya bean genotypes. A glasshouse soil trap experiment using soil samples collected from Lothair, Bothaville, and Standerton was performed on five cultivars. The trapped rhizobial strains were further screened in the glasshouse to authenticate their nodulation compatibility with the different soya bean cultivars. The rhizobial strains showed significant nodulation compatibility with the selected cultivars. These strains were also tested for beneficial traits in vitro and characterized using DNA sequencing methods to elucidate their taxonomic identity. Some of the most nodulation-compatible strains characterized as Bradyrhizobium and Sinorhizobium species exhibited significant symbiotic performance in terms of plant biomass, nodule number, and nodule dry weight. The study generated valuable data that provide information on the extent of symbiotic compatibility of some of the existing cultivars used in South Africa with native rhizobia and whether inoculation of soya bean with commercial products is vital on some soya bean farms. [ABSTRACT FROM AUTHOR]

Prolonged inoculation of soya bean (Glycine max L.) farms with exotic strains of Bradyrhizobium species starting in the 1960s resulted in the establishment of populations of Bradyrhizobium strains in the soils of several soya bean farms in South Africa. With the increasing number of new soya bean genotypes in the country, it is challenging to determine which genotypes are highly compatible with a given rhizobium strain. In this study, we investigated the symbiotic compatibility of native rhizobial isolates and the strains from the South African Rhizobium Culture Collection (SARCC) on ten selected locally available soya bean genotypes. A glasshouse soil trap experiment using soil samples collected from Lothair, Bothaville, and Standerton was performed on five cultivars. The trapped rhizobial strains were further screened in the glasshouse to authenticate their nodulation compatibility with the different soya bean cultivars. The rhizobial strains showed significant nodulation compatibility with the selected cultivars. These strains were also tested for beneficial traits in vitro and characterized using DNA sequencing methods to elucidate their taxonomic identity. Some of the most nodulation-compatible strains characterized as Bradyrhizobium and Sinorhizobium species exhibited significant symbiotic performance in terms of plant biomass, nodule number, and nodule dry weight. The study generated valuable data that provide information on the extent of symbiotic compatibility of some of the existing cultivars used in South Africa with native rhizobia and whether inoculation of soya bean with commercial products is vital on some soya bean farms.

Background. Increasing the yield of soybean necessitates the maintenance of a high protein level in seeds, and therefore the process of fixing atmospheric N2. Seed inoculation with soybean nitrogen-fixing bacteria is known to improve N2-fixation and soybean grain yield. At the same time, the introduction of new nodule bacteria strains into preparations for soybean inoculation requires the study of their influence on the main interconnected physiological processes that form the basis of leguminous plants productivity – N2-fixation and photosynthesis. The aim of the work was to study the relationship of vegetative growth and grain productivity of soybean inoculated with new nodule bacteria Bradyrhizobium japonicum strains of different functional activity with the plants’ symbiotic and photosynthetic apparatuses functioning. Materials and Methods. The research was carried out on symbiotic systems created with soybean plants (Glycine max (L.) Merr.) of the Almaz variety and nodule bacteria B. japonicum strains: analytically selected PC09, and recombinant strains B157, B201, D45, D52 (pSUP5011::Tn5mob) and C30 (pSUP2021::Tn5) from the N2-fixing microorganisms museum collection of the Institute of Plant Physiology and Genetics NAS of Ukraine. Research methods – microbiological, biochemical and physiological, statistical analysis. Results. It was found that the N2-fixing activity (NFA) of nodules formed by B. japoni­cum PC09, D45, D52, B157 and B201 strains at the stage of 3 true leaves exceeded the NFA of nodules formed by Tn5-mutant C30 by 1.6–4.0 times, and at the stage of budding–beginning of flowering – by 4.2–6.2 times. Highly active strains also differed from each other in NFA, although to a lesser extent than with strain C30. On the basis of a comparative analysis of the physiological indices of soybean inoculated with B. japonicum strains of different activity, close positive linear correlations were found between NFA, photosynthetic rate, and the biological and grain productivity of plants. Conclusions. The results obtained indicate that the higher the nodulating and NFA of rhizobia in the symbiotic system soybean–Bradyrhizobium japonicum, the higher the functional activity of photosynthetic apparatus formed by plants. This provides a more complete genetic potential release of soybean crop productivity.

Legumes Lessertia diffusa and Calobota sericea, indigenous to South Africa, are commonly used as fodder crops with potential for sustainable livestock pasture production. Rhizobia were isolated from their root nodules grown in their respective soils from the Succulent Karoo biome (SKB) in South Africa, identified and characterized using a polyphasic approach. Sequence analysis of the 16S rRNA gene confirmed all isolates as Mesorhizobium members, which were categorized into two distinct lineages using five housekeeping protein-coding genes. Lineage I included 14 strains from both legumes, while Lineage II comprised a single isolate from C. sericea. Differences in phenotypic traits were observed between the lineages and corroborated by average nucleotide identity analyses. While all strains nodulated their original hosts, strains from C. sericea failed to effectively nodulate L. diffusa and vice versa. Phylogenetic analyses of nitrogen fixation (nifH) and nodulation (nodA, nodC) loci grouped all strains in a single clade, suggesting that unique symbiotic loci determine nodulation of these legumes. We designated Lineage I and II as Mesorhizobium salmacidum sp. nov. (Ld1326Ts; GCA_037179605.1Ts) and Mesorhizobium argentiipisi sp. nov. (Cs1330R2N1Ts; GCA_037179585.1Ts), using genome sequences as nomenclatural types according to the Nomenclatural Code for Prokaryotes using Sequence Data, thus avoiding complications with South Africa's biodiversity regulations. Identifying effective microsymbionts of L. diffusa and C. sericea is essential for conservation of Succulent Karoo Biome, where indigenous invasive species like Vachellia karroo and non-native Australian acacia species are present. Furthermore, targeted management practices using effective symbionts of the studied legumes can sustain the biome's socio-economic contribution through fodder provision. [ABSTRACT FROM AUTHOR]

Molecular interspecies dialogue between leguminous plants and nitrogen-fixing rhizobia results in the development of symbiotic root nodules. This is initiated by several nodulation-related receptors present on the surface of root hair epidermal cells. We have shown previously that specific subunits of heterotrimeric G-proteins and their associated regulator of G-protein signaling (RGS) proteins act as molecular links between the receptors and downstream components during nodule formation in soybeans. Nod factor receptor 1 (NFR1) interacts with and phosphorylates RGS proteins to regulate the G-protein cycle. Symbiosis receptor-like kinases (SymRK) phosphorylate Gα to make it inactive and unavailable for Gβγ. We now show that like NFR1, SymRK also interacts with the RGS proteins to phosphorylate them. Phosphorylated RGS has higher activity for accelerating guanosine triphosphate (GTP) hydrolysis by Gα, which favors conversion of active Gα to its inactive form. Phosphorylation of RGS proteins is physiologically relevant, as overexpression of a phospho-mimic version of the RGS protein enhances nodule formation in soybean. These results reveal an intricate fine-tuning of the G-protein signaling during nodulation, where a negative regulator (Gα) is effectively deactivated by RGS due to the concerted efforts of several receptor proteins to ensure adequate nodulation. [Figure: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Autophagy is a genetically regulated, eukaryotic catabolic pathway that responds to internal and external cellular signals. In plants, it plays crucial roles in development, and responses to abiotic and biotic stresses. Due to its role in limiting the hypersensitive response, research on the molecular mechanisms of autophagic signalling pathways in plant–microbe interactions has primarily focused on plant–pathogen responses. Although there is substantially less information on the role of autophagy signalling in symbiotic plant–microbe interactions, there is accumulating evidence that it is also a key regulator of mutualistic plant–microbe interactions. Here, we review recent progress on the roles of autophagy in symbiotic plant interactions and discuss potential future research directions. Once understood, the central role that autophagy plays within pathogenic and symbiotic plant–microbe interactions has significant potential application for crop improvement. Manipulating autophagy in legume crops could help support crop growth with reduced levels of fertiliser application while maintaining yields with increased protein content in the harvest. [ABSTRACT FROM AUTHOR]

Introduction: Plants strictly control root endosymbioses with nutrient-scavenging arbuscular endomycorrhizal fungi or nodule inducing diazotrophic bacteria. The GRAS-type transcriptional regulator NODULATION SIGNALING PATHWAY 2 (NSP2) is a conserved hub in this process. The NSP2 -regulated transcriptional network is instrumental in balancing nutrient homeostasis with symbiotic interactions. NSP2 activity is modulated post-transcriptionally by a specific microRNA. Overriding this control mechanism by ectopic expression of a miRNA-resistant NSP2 transgene enhances the symbiotic permissiveness to arbuscular endomycorrhizal fungi. Such engineered plants may possess enhanced capacities for nutrient uptake. However, the trade-off of this strategy on plant development or other symbiotic interactions, like nodulation, is yet to be fully understood. Method: We used the nodulating Cannabaceae species Parasponia andersonii as an experimental system to study the effect of ectopic NSP2 expression. Parasponia and legumes (Fabaceae) diverged 100 million years ago, providing a unique comparative system to dissect the nodulation trait. Results: Six independent transgenic Parasponia lines were generated that differed in the level of NSP2 expression in the root from 6 to 95-fold higher when compared to the empty vector control plants. Analysis of these plants revealed a positive correlation between mycorrhization and the NSP2 expression level, as well as with the expression of the symbiosis transcription factor CYCLOPS and the rate-limiting enzyme in the carotenoid biosynthetic pathway PHYTOENE SYNTHASE1 (PSY1). Yet ectopic expression of NSP2 affected plant architecture and root nodule organogenesis. Discussion: This indicates a significant trade-off when leveraging NSP2 over-expression to enhance endomycorrhization. [ABSTRACT FROM AUTHOR]

Cell-cell communication is essential for both unicellular and multicellular organisms. Secreted peptides that act as diffusive ligands are utilized by eukaryotic organisms to transduce information between cells to coordinate developmental and physiological processes. In plants, The CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) genes encode a family of secreted small peptides which play pivotal roles in stem cell homeostasis in various types of meristems. Accumulated evidence has revealed that CLE peptides mediate trans-kingdom interactions between plants and microbes, including pathogens and symbionts. This review highlights the emerging roles of CLE peptide signaling in plant-microbe interactions, focusing on their involvement in nodulation, immunity, and symbiosis with arbuscular mycorrhizal fungi. Understanding these interactions provides insights into the sophisticated regulatory networks to balance plant growth and defense, enhancing our knowledge of plant biology and potential agricultural applications. [ABSTRACT FROM AUTHOR]

The regulation of legume‐rhizobia symbiosis by microorganisms has obtained considerable interest in recent research, particularly in the common rhizobacteria Bacillus. However, few studies have provided detailed explanations regarding the regulatory mechanisms involved. Here, we investigated the effects of Bacillus (Bac.B) on Bradyrhizobium–soybean (Glycine max) symbiosis and elucidated the underlying ecological mechanisms. We found that two Bradyrhizobium strains (i.e. Bra.Q2 and Bra.D) isolated from nodules significantly promoted nitrogen (N) efficiency of soybean via facilitating nodule formation, thereby enhanced plant growth and yield. However, the intrusion of Bac.B caused a reverse shift in the synergistic efficiency of N2 fixation in the soybean–Bradyrhizobium symbiosis. Biofilm formation and naringenin may be importantin suppression of Bra.Q2 growth regulated by Bac.B. In addition, transcriptome and microbiome analyses revealed that Bra.Q2 and Bac.B might interact to regulateN transport and assimilation, thus influence the bacterial composition related to plant N nutrition in nodules. Also, the metabolisms of secondary metabolites and hormones associated with plant–microbe interaction and growth regulation were modulated by Bra.Q2 and Bac.B coinoculation. Collectively, we demonstrate that Bacillus negatively affects Bradyrhizobium–soybean symbiosis and modulate microbial interactions in the nodule. Our findings highlight a novel Bacillus‐based regulation to improve N efficiency and sustainable agricultural development. Summary Statement: We found a Bacillus, isolated from nodule, inhibited N efficiency in soybean–Bradyrhizobium symbiosis, mainly by restraining biofilm formation and naringenin‐regulated growth of Bradyrhizobium, regulating N, flavonoid, hormone metabolic pathways and beneficial bacteria composition in nodule. [ABSTRACT FROM AUTHOR]

Introduction: The chickpea (Cicer arietinum L.) is well-known for having climate resilience and atmospheric nitrogen fixation ability. Global demand for nitrogenous fertilizer is predicted to increase by 1.4% annually, and the loss of billions of dollars in farm profit has drawn attention to the need for alternative sources of nitrogen. The ability of chickpea to obtain sufficient nitrogen via its symbiotic relationship with Mesorhizobium ciceri is of critical importance in determining the growth and production of chickpea. Methods: To support findings on nodule formation in chickpea and to map the genomic regions for nodulation, an association panel consisting of 271 genotypes, selected from the global chickpea germplasm including four checks at four locations, was evaluated, and data were recorded for nodulation and 12 yield-related traits. A genome-wide association study (GWAS) was conducted using phenotypic data and genotypic data was extracted from whole-genome resequencing data of chickpea by creating a hap map file consisting of 602,344 single-nucleotide polymorphisms (SNPs) in the working set with best-fit models of association mapping. Results and Discussion: The GWAS panel was found to be structured with sufficient diversity among the genotypes. Linkage disequilibrium (LD) analysis showed an LD decay value of 37.3 MB, indicating that SNPs within this distance behave as inheritance blocks. A total of 450 and 632 stringent marker-trait associations (MTAs) were identified from the BLINK and FarmCPU models, respectively, for all the traits under study. The 75 novel MTAs identified for nodulation traits were found to be stable. SNP annotations of associated markers were found to be related to various genes including a few auxins encoding as well as nod factor transporter genes. The identified significant MTAs, candidate genes, and associated markers have the potential for use in marker-assisted selection for developing high-nodulation cultivars after validation in the breeding populations. [ABSTRACT FROM AUTHOR]

The continuous release of glucosinolates into the soil by Brassicaceae root exudation is a prerequisite to maintaining toxic levels of breakdown products such as isothiocyanates (ITCs). ITCs influence plant and microbial diversity in ecosystems, while fungi and Rhizobiaceae are particularly injured. Studies explaining the molecular mechanisms of the negative effects are presently limited. Therefore, we investigated the early effects of cyclic ITC goitrin on proteomes of the host and symbiotic Mesorhizobium loti in the nodules of Lotus japonicus and of free-living bacteria. In the nodules, many host proteins had a higher abundance, among them, peroxidases and pathogenesis-related PR-10 proteins functioning in the abscisic-acid-activated signaling pathway. In the microsymbiont, transporter proteins as a prominent group are enhanced; some proteins involved in N-fixation decreased. The proteomes give a report about the loss of immunity suppression resulting in the termination of symbiosis, which initiates nodule senescence. Free-living M. loti are severely damaged, indicated, i.a., by a decrease in transporter proteins, the assumed candidates for goitrin protein complex formation, and high proteolysis. The production of chicoric acid by the accompanying bacteria is inhibitory for M. loti but connected to goitrin elimination, as confirmed by mass spectrometric (MS) analysis. In summary, the nodulation process is severely affected by goitrin, causing nodule dysfunction and failed nodule development. N deficiency conditions leads to yellowish leaves and leaf abscission. [ABSTRACT FROM AUTHOR]

The present study aimed to rapidly screen all the isolated fifty-two rhizobia (CPGR-1 to CPGR-52) for effective nodulation in groundnut using sterilized vermiculite as a medium for 40 days. Sterilized vermiculite was used for filling in polythene bags. The vermiculite surface was covered with sterile cotton to protect it from aerial contamination. The N-free nutrient solution was applied daily whereas the uninoculated control was supplemented with KNO3. Groundnut seeds were surface sterilized and sown aseptically in plastic polythene bags containing presterilized vermiculite. After seed germination two seedlings per pot were retained then one ml of the broth culture was poured around the seedling soon after germination of the seed with the help of a sterile pipette. Two replications were maintained for each treatment. The control plants were not inoculated. After 40 DAS, the plants were observed for a significantly increased number of effective nodules per plant, effective nodule dry weight (mg/plant), root length (cm), root weight (g/plant), total dry biomass (g/plant), shoot N content (%), root N content (%). Based on nodule number and total plant N content (at 40 DAS), the four best isolates (CPGR-8, CPGR-49, CPGR-33 and CPGR-52) were selected as efficient rhizobial strains which can help in overall plant growth and development sustainably also retaining soil fertility. [ABSTRACT FROM AUTHOR]

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This study identified the phenotypic and genotypic characteristics of the bacteria that nodulate wild Lathyrus and Vicia species natural distribution in the Gaziantep province of Turkey. Principle component analysis of phenotypic features revealed that rhizobial isolates were highly resistant to stress factors such as high salt, pH and temperature. They were found to be highly sensitive to the concentrations (mg/mL) of the antibiotics neomycin 10, kanamycin, and tetracycline 5, as well as the heavy metals Ni 10, and Cu 10, and 5. As a result of REP-PCR analysis, it was determined that the rhizobial isolates were quite diverse, and 5 main groups and many subgroups being found. All of the isolates nodulating wild Vicia species were found to be related to Rhizobium sp., and these isolates were found to be in Clades II, III, IV, and V of the phylogenetic tree based on 16S rRNA. The isolates that nodulated wild Lathyrus species were in Clades I, II, IV, V, VI, VII, and VIII, and they were closely related to Rhizobium leguminasorum, Rhizobium sp., Phyllobacterium sp., Serratia sp., and Pseudomonas sp. According to the genetic analyses, the isolates could not be classified at the species level, the similarity ratio was low, they formed a distinct group that was supported by strong bootstrap values in the phylogenetic tree, and the differences discovered in the network analysis revealed the diversity among the isolates and gave important findings that these isolates may be new species. [ABSTRACT FROM AUTHOR]

Various species of rhizobium establish compatible symbiotic relationships with soybean (Glycinemax) leading to the formation of nitrogen-fixing nodules in roots. The formation of functional nodules is mediated through complex developmental and transcriptional reprogramming that involves the activity of thousands of plant genes. However, host transcriptome that differentiate between functional or nonfunctional nodules remain largely unexplored. In this study, we investigated differential compatibilities between rhizobium strains (Bradyrhizobium diazoefficiens USDA110 Bradyrhizobium sp. strain LVM105) and cultivated and wild soybeans. The nodulation assays revealed that both USDA110 and LVM105 strains effectively nodulate G. soja but only USDA110 can form symbiotic relationships with Williams 82. LVM105 formed pseudonodules on Williams 82 that consist of a central nodule-like mass that are devoid of any rhizobia. RNA-seq data revealed that USDA110 and LVM105 induce distinct transcriptome programing in functional mature nodules formed on G. soja roots, where genes involved in nucleosome assembly, DNA replication, regulation of cell cycle, and defense responses play key roles. Transcriptome comparison also suggested that activation of genes associated with cell wall biogenesis and organization and defense responses together with downregulation of genes involved in the biosynthesis of isoprenoids and antioxidant stress are associated with the formation of non-functional nodules on Williams 82 roots. Moreover, our analysis implies that increased activity of genes involved in oxygen binding, amino acid transport, and nitrate transport differentiates between fully-developed nodules in cultivated versus wild soybeans. [ABSTRACT FROM AUTHOR]

We collected soil samples from six major mung bean cropping regions in Myanmar: Sagaing, Mandalay, Nay Pyi Taw, and Magway in the tropical savanna climate zone and Bago and Yangon in the tropical monsoon climate zone. All fields grew mung bean for at least 5 years and had no history of rhizobial inoculation. Mung bean 'Yezin-11', a popular cultivar in Myanmar, was inoculated with soil suspensions. From the nodules formed on the roots, we isolated 55 rhizobial strains. Identification of the isolates revealed the dominant species of indigenous rhizobia in each region. We identified 53 Bradyrhizobium strains and 2 Ensifer strains. Bradyrhizobium yuanmingense was dominant in the tropical savanna zone and Bradyrhizobium sp. (B. liaoningense or B. diversitatis) and B. centrosematis were dominant in the tropical monsoon zone. Principal component analysis indicates that the dominance of B. yuanmingense in the tropical savanna zone might be due to high concentration of NO3-N and P2O5 in the soil. It also indicates that the dominance of B. centrosematis in the tropical monsoon zone might be caused by drastically low pH and high concentration of NH4 in the soil. Bradyrhizobium centrosematis YGN-M9, B. yuanmingense SGG-M3, and Bradyrhizobium sp. BGO-M5 significantly increased nodulation (nodule number and nodule dry weight), acetylene reduction activity, and shoot dry weight, respectively, relative to Ensifer terangae MDY-M6. Co-inoculation with these three strains increased nodulation significantly compared with single inoculation of BGO-M5. The characterization of mung bean rhizobia and selection of microbial inoculant candidates will be useful for the development of microbial inoculants in Myanmar. [ABSTRACT FROM AUTHOR]

Purpose: Organomineral fertilizer using wood ash, an agro-industrial waste, as an organic material has potential in agriculture as an alternative fertilizer. The objective was to evaluate the effects of the use of organomineral fertilizers from wood ash in comparison with conventional mineral fertilization in the cultivation of cowpea in acid tropical soil. Method: The experimental design used was randomized blocks, in a 4x3 factorial scheme, corresponding to three levels of base saturation (no liming - 0%, V = 30% and V = 60%), and four fertilization treatments: mineral, wood ash, organomineral and granulated organomineral, with four replications. The soil used was Oxisol. To produce organomineral fertilizer – wood ash and mineral fertilizers were used as organic raw material. The fertilizer granulated organomineral used the same composition as the organomineral. The test crop used was cowpea. Results: The highest soil pH values of 6.8 and 6.2 were observed at 30 days after emergence in wood ash and organomineral fertilizers, respectively. The organomineral fertilizer provided the highest shoot dry mass (23.0 g/pot) when no lime was applied, when compared to the other fertilizers. The highest grain yield of cowpea was observed in wood ash and organomineral, in the absence of liming. The nodulation capacity of cowpea plants was reduced when lime was applied (V = 30% and 60%) and fertilized with wood ash and organomineral. Conclusion: The transformation of wood ash into organomineral fertilizer proved to be a promising step in converting a solid waste into a commercially viable agricultural fertilizer. Research Highlights • Eucalyptus sp. ash has positive agronomic effects for cowpeas; • The effects of ash and organominerals on soil pH are observed in the short term; • The non-granulated organomineral provides greater productivity for cowpeas; • Ash and organominerals reduce bean nodules as the dose of lime increases; • Organomineral is an alternative fertilizer for growing cowpeas

Non-halophytic plants are highly susceptible to salt stress, but numerous studies have shown that halo-tolerant microorganisms can alleviate this stress by producing phytohormones and enhancing nutrient availability. This study aimed to identify and evaluate native microbial communities from salt-affected regions to boost black gram (Vigna mungo) resilience against salinity, while improving plant growth, nitrogen uptake, and nodulation in saline environments. Six soil samples were collected from a salt-affected region in eastern Uttar Pradesh, revealing high electrical conductivity (EC) and pH, along with low nutrient availability. A total of 72 bacterial strains were isolated from soil and 28 from black gram (Vigna mungo) root nodules, with 32 of the soil bacteria tolerating up to 10% NaCl. These bacteria were characterized through taxonomic and biochemical tests. Cross-compatibility analysis showed two rhizobia strains were highly compatible with five salt-tolerant bacteria. These strains exhibited significant plant growth-promoting traits, including phosphate, potassium, and zinc solubilization, as well as ACC deaminase, IAA, siderophore, and EPS production. Strain Paenibacillus sp. SPR11 showed the strongest overall performance. Genetic diversity was assessed using BOX-PCR and ERIC-PCR, and strains were identified through 16S rRNA gene sequencing. In a seed germination study under saline conditions (200 mM and 300 mM), co-inoculation with Bradyrhizobium yuanmingense PR3 and Paenibacillus sp. SPR11 resulted in a significant enhancement in seed germination (40%), root growth (84.45%), and shoot growth (90.15%) compared to single inoculation of B. yuanmingense PR3. Under greenhouse conditions in Leonard jars, co-inoculation with strains PR3 and SPR11 significantly enhanced shoot and root length, fresh and dry biomass, nodule count, and nodule fresh and dry weight. Chlorophyll content, nutrient uptake, and crude protein levels increased, while proline content decreased compared to single inoculation and uninoculated seeds. Our best understanding leads us to believe that this is the very first report of utilizing co-inoculation of salt-tolerant Paenibacillus sp. SPR11 and B. yuanmingense PR3, demonstrating their promising potential to alleviate salt stress and enhance growth, root architecture, nitrogen uptake, and nodule formation in black gram under nitrogen free saline conditions.

Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plant’s need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of nodulation (AON) and autoregulation of mycorrhizal symbiosis (AOM) both negatively regulate their respective processes and share multiple components—plants that make too many nodules usually have higher arbuscular mycorrhiza (AM) fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus. Medicago truncatula has two sequence homologs: MtTML1 and MtTML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR–Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in MtTML1 or MtTML2 produced two to three times the nodules of wild-type plants, whereas plants containing mutations in both genes displayed a synergistic effect, forming 20× more nodules compared to wild-type plants. Examination of expression and heterozygote effects suggests that genetic compensation may play a role in the observed synergy. Plants with mutations in both TMLs only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting that these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of MtTML1 and MtTML2 in M. truncatula symbiosis with beneficial microbes.

Paraburkholderia phytofirmans PsJN is a plant symbiotic bacterium that can colonize a broad spectrum of plant hosts and frequently shows beneficial effects on plant growth. Exopolysaccharide (EPS) is known to be important in plantbacteria interactions. Previously, we reported that EPS is required for PsJN to survive from drought stress and colonize in pea (Pisum sativum) under drought condition. However, whether EPS is necessary for PsJN to promote plant growth remains unknown. In this work, a comparative study was conducted between the wild-type PsJN and its ΔbceQ mutant that lacks EPS to investigate the role of EPS in PsJN to confer drought-stress tolerance on pea plant. Our results showed that wild type PsJN, but not the ΔbceQ mutant, promoted pea seed germination and seedlings growth under drought stress. Pea plants inoculated with the wild type PsJN had a higher level of drought tolerance, as shown by a better vegetative growth and enhanced nodule formation, than plants inoculated with the ΔbceQ mutant. Moreover, EPS plays a role in the plant colonization under drought stress, because the ΔbceQ mutant was unable to colonize pea seeds and roots as effectively as the wild type PsJN. Further, expression of the EPS biosynthesis genes in the bceOVN operon of the wild type PsJN was induced by the presence of glucose. Overall, this study demonstrated that PsJN can promote pea plant growth under drought conditions and EPS is required for PsJN to confer beneficial effects to host plant. [ABSTRACT FROM AUTHOR]

Viruses, bacteria, fungus, protozoans, and different metazoan parasites and parasitoids present a constant threat to insects. Insect immunity has two components: humoral and cell mediated. Humoral immunity can be achieved by various antimicrobial proteins, namely, cecropins, sarcotoxin, defensin, attacin, etc. The cell‐mediated immunity comprises various cells having immune functions fostering nodulation, phagocytosis, microaggregation, encapsulation etc. Eicosanoids play a crucial role in insect immunity comparable to other animals. The above‐mentioned are signaling molecules derived from polyunsaturated fatty acids and they exert numerous physiological effects, namely, inflammation, immune modulation, and regulation of cellular processes. The review article elucidates various roles of eicosanoids, namely, nodulation reaction, Toll signaling pathway, nitric oxide (NO) generation, Ca2+ mobilization, production of reactive oxygen species (ROS), actin polymerization and aquaporin activation. Eicosanoids can function in immune priming in insects drawing hemocytes. An agent named Duox was also identified serving as ROS generator in insect gut. Moreover, role of Repat gene in insect immunity was also studied. However, recently the role of prostacyclin (PGI2) was found to be negative as it inhibits platelet aggregation. In this brief review, we have tried to shed light on the various functions of eicosanoids in immunity of insect those have been discovered recently. This concise study will allow to decipher eicosanoids’ function in insect immunity in a nutshell, and it will pave the way for more researches to understand the key players of insect immunity which may eventually help to develop novel vector and pest control strategies in near future. [ABSTRACT FROM AUTHOR]

Background and aims: While the effects of fertilizer nitrogen (N) on N fixation in soybean nodules lead to both local inhibition and systemic regulation, the specific mechanism is not clear. This study aimed to elucidate the mechanism by which systemic N regulation affects soybean root growth and N fixation. Methods: Dual-root soybean plants containing unilateral nodulation were cultivated using grafting and sand culture with the addition of N-containing nutrient solution to the non-nodulated root portion and N-free nutrient solution to the nodulated portion during the VC-R1 period (28 d). The effects of N supplementation on changes in the expression of genes and proteins, as well as metabolite levels, in nodules and roots were examined, together with an evaluation of alterations in metabolic pathways in response to the indirect N supply. Results: The results demonstrated that a 28-day supply of N to non-nodulated part of the root reduced nodulation while promoting the growth of the root system on the nodulation side. A comparative evaluation of the soybean plants cultivated with and without N supplementation revealed that N promoted the synthesis of signaling compounds, such as asparagine and trehalose, in nodules and inhibited flavonoid-associated metabolic pathways. Starch syntheis in nodules under long-term high-N was inhibited while the metabolism of organic acids was enhanced. Long-term indirect N supply also influenced pathways associated with amino acid metabolism and phenylpropanoid biosynthesis pathway in the roots. Conclusion: The different response metabolic pathways of roots and nodules supported the different characteristics of soybean roots and nodules after indirect nitrogen supply. Additionally, the duration of nitrogen supply affects the regulatory pathway of nitrogen fixation of nodules. [ABSTRACT FROM AUTHOR]