1 Introduction

The symbiotic relationship between legumes and rhizobia has been a subject of scientific inquiry for over a century. This mutualistic association, where rhizobia fix atmospheric nitrogen into a form usable by plants, is crucial for the growth of legumes in nitrogen-poor soils. The discovery of this symbiosis has significantly advanced our understanding of plant-microbe interactions and has had profound implications for agricultural practices (Wang et al., 2012; Wang et al., 2018).

Legumes are a vital component of sustainable agriculture due to their ability to improvesoil fertility through biological nitrogen fixation. This process reduces the need for synthetic nitrogen fertilizers, which are costly and environmentally damaging. Legumes also play a crucial role in crop rotation systems, enhancing soil health and productivity (Oldroyd et al., 2011; Wang et al., 2020; Yang et al., 2021). The economic and ecological benefits of legumes underscore the importance of understanding and optimizing their symbiotic relationship with rhizobia (Chakraborty et al., 2022; Hawkins and Oresnik, 2022).

This study aims to delve into the genetic and molecular mechanisms that underpin the legume-rhizobium symbiosis. By examining the specific genes and signals involved in the establishment and maintenance of this symbiosis, this study seeks to provide a comprehensive overview of how these interactions are regulated at the genetic level. Understanding these mechanisms is essential for developing strategies to enhance the efficiency of nitrogen fixation and improve legume crop yields. In addition to exploring the genetic aspects, this study will highlight practical applications of rhizobium-legume symbiosis in agriculture. This study will discuss how insights from genetic studies can be applied to develop more effective inoculants, improve crop management practices, and ultimately enhance legume crop performance. By integrating genetic insights with practical applications, this study aims to provide a holistic approach to leveraging the benefits of rhizobium-legume symbiosis for sustainable agriculture.

2 Overview of Rhizobium-Legume Symbiosis

2.1 Biological basis of symbiosis

The symbiotic relationship between rhizobia and legumes is a classic example of mutualism, where both partners derive significant benefits. Legumes provide rhizobia with carbohydrates and a niche within root nodules, while rhizobia fix atmospheric nitrogen (N2) into ammonia, which is assimilated by the plant for growth and development. This biological nitrogen fixation is crucial for improving soil fertility and reducing the need for chemical fertilizers, making it an environmentally friendly alternative (Mendoza-Suárez et al., 2021).

The process of nitrogen fixation in rhizobium-legume symbiosis involves several stages, starting with the exchange of chemical signals between the plant and the bacteria. Rhizobia produce Nod factors that are recognized by specific receptors on the legume roots, initiating nodule formation. Within these nodules, rhizobia convert atmospheric nitrogen into ammonia through the action of the nitrogenase enzyme complex. This ammonia is then assimilated by the plant, providing a vital source of nitrogen for its growth (Clúa et al., 2018; Wang et al., 2018; Yang et al., 2021).

2.2 Rhizobium species and their specificity

Rhizobia are a diverse group of bacteria, primarily classified into alpha- and beta-proteobacteria. Key genera include Rhizobium, Bradyrhizobium, Ensifer (formerly Sinorhizobium), and Mesorhizobium, among others. Each genus contains multiple species and strains, each with varying abilities to form symbiotic relationships with different legume hosts (Masson-Boivin et al., 2009; Andrews and Andrews, 2016). The specificity of rhizobium-legume interactions is a complex trait influenced by both the bacterial and plant genomes. Specificity can occur at multiple stages of the symbiotic process, from initial bacterial attachment to nodule development and nitrogen fixation. For instance, Bradyrhizobium spp. are typically associated with legumes in the Caesalpinioideae sub-family, while Rhizobium and Ensifer species are more common in the Papilionoideae sub-family. Some legumes exhibit promiscuity, nodulating with multiple rhizobial species, whereas others show strict specificity (Figure 1) (Wang et al., 2012; Andrews and Andrews, 2016; Wang et al., 2018).

Host specificity is also influenced by environmental factors and the presence of native rhizobial populations in the soil. For example, Mimosa species in Brazil show specificity towards Burkholderia, while in Mexico, they prefer Rhizobium/Ensifer, and in Uruguay, Cupriavidus is the preferred symbiont. This specificity is often related to the relative abundance of these rhizobia in different soils (Andrews and Andrews, 2016; Mendoza-Suárez et al., 2021; Chakraborty et al., 2022). In summary, the rhizobium-legume symbiosis is a finely tuned interaction with significant implications for agricultural productivity and sustainability. Understanding the genetic and environmental factors that influence this symbiosis can lead to the development of more effective biofertilizers and improved legume crop yields.

3 Genetic Insights into Rhizobium-Legume Interaction

3.1 Molecular genetics of rhizobium

The genomic structure of Rhizobium species is complex and includes both chromosomal and plasmid-borne genes essential for symbiosis and nitrogen fixation. For instance, Rhizobium sp. NGR234 possesses two dicarboxylate transport systems, one located on the chromosome and the other on a symbiotic plasmid, which are crucial for nitrogen fixation in tropical legumes. Additionally, the genomes of several Rhizobium species have been sequenced, revealing key genes involved in symbiotic nitrogen fixation (SNF) and providing insights into their functional roles (Dall’Agnol et al., 2014; Dwivedi et al., 2015).

The regulation of nitrogen fixation genes in Rhizobium is tightly controlled and involves various genetic and environmental factors. For example, the dctA gene in Rhizobium sp. NGR234, which is essential for dicarboxylate transport and nitrogen fixation, is regulated by unique promoter sequences distinct from those in other Rhizobium species. Moreover, proteomic studies have identified host factors, such as bioactive peptides, that control gene expression in the symbiont, further elucidating the regulatory mechanisms of nitrogen fixation (Marx et al., 2016; Allito et al., 2020).

3.2 Host plant genetics

The formation of nodules in legumes is a genetically complex process involving multiple genes. Quantitative trait loci (QTL) and candidate genes underlying nodule formation have been identified in various legumes, including soybean and common bean (Dwivedi et al., 2015). These genes are crucial for the establishment and maintenance of the symbiotic relationship between the host plant and Rhizobium (Wang et al., 2018).

Plant receptors and signaling pathways play a pivotal role in the recognition and establishment of symbiosis with Rhizobium. For instance, calmodulin-binding proteins have been identified as key regulators in the host plant, mediating the signaling pathways that control nodule formation and function (Dwivedi et al., 2015). Additionally, microRNAs (miRNAs) are essential for coordinating various plant processes required for nodule formation and function, impacting hormone signaling and spatial regulation of gene expression (Hoang et al., 2020; Abdelkhalek et al., 2022).

3.3 Advances in genomic techniques

Advances in sequencing technologies have significantly contributed to our understanding of rhizobium-legume interactions. The genomes of several legume species, such as chickpea, pigeonpea, and soybean, as well as multiple Rhizobium species, have been sequenced, providing valuable genetic information for improving SNF and legume productivity (Dwivedi et al., 2015). These genomic resources facilitate the identification of DNA markers and the exploration of genotype-phenotype relationships in SNF.

Gene editing technologies, such as CRISPR/Cas9, have opened new avenues for functional genomics studies in rhizobium-legume symbiosis. These techniques allow precise manipulation of genes involved in SNF, enabling researchers to dissect their roles and improve symbiotic efficiency. For example, synthetic biology approaches are being employed to engineer new symbiotic interactions or enhance existing ones, leveraging the knowledge gained from genome- and systems-level studies (Figure 2) (diCenzo et al., 2018). By integrating these genetic insights and advanced genomic techniques, researchers can develop legume cultivars with enhanced symbiotic efficiency, ultimately contributing to sustainable agricultural practices and improved crop yields.

4 Rhizobium Genetic Diversity and Adaptation

4.1 Genetic variability among Rhizobium strains

Rhizobium strains exhibit significant genetic variability, which is reflected in their strain-specific traits. For instance, Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 possess a highly conserved symbiotic plasmid (pSym) that includes three distinct nodA genes, contributing to their broad host range and adaptability to various legume hosts. Additionally, these strains have numerous genes encoding drug-efflux systems, which confer high resistance to antimicrobials and enable them to thrive in diverse environmental conditions (Ormeño-Orrillo et al., 2012). The genetic diversity among Rhizobium leguminosarum biovar viciae strains also highlights the specificity of symbiotic partnerships, with certain genotypes favoring specific legume hosts such as broad bean (Vicia faba) (Mutch and Young, 2004).

The genetic variability among Rhizobium strains directly impacts their symbiotic efficiency. Studies have shown that the presence of specific genetic elements, such as the nodulation genes in Rhizobium leguminosarum, can influence the effectiveness of nitrogen fixation and the overall fitness of both the host plant and the Rhizobium (Mutch and Young, 2004). Furthermore, the alignment of fitness between host and symbiont is crucial, as ineffective rhizobia are often ‘defective’ rather than ‘defectors’, indicating that genetic mutations can enhance the symbiotic relationship (Friesen, 2012). The interaction between light availability and Rhizobium strain variation also plays a role in determining the growth and nutrient composition of legume hosts, further emphasizing the importance of genetic diversity in symbiotic efficiency (Heath et al., 2020).

4.2 Adaptation to environmental stress

Rhizobium strains have developed various adaptations to cope with environmental stresses such as drought, salinity, and pH fluctuations. For example, Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 are well-equipped to handle low pH, high temperatures, and oxidative and osmotic stresses, which are common in tropical environments. The genetic determinants for these stress responses include genes involved in the biosynthesis and modulation of plant-hormone levels, as well as those encoding surface polysaccharides, uptake transporters, and catabolic enzymes for nutrients (Ormeño-Orrillo et al., 2012). Additionally, the GSK3-like kinase GmSK2-8 in soybean has been identified as a key regulator that inhibits symbiotic signaling and nodule formation under salt stress, highlighting the genetic mechanisms underlying stress tolerance in legume-rhizobium symbiosis (Figure 3) (He et al., 2020).

The genetic mechanisms that confer stress tolerance in rhizobia are diverse and complex. Genome sequencing of Rhizobium strains has revealed a wide array of genes involved in stress response, including those encoding drug-efflux systems, iron-acquisition systems, and cell wall-degrading enzymes (Ormeño-Orrillo et al., 2012). These genetic traits enable rhizobia to persist and compete in challenging environments, thereby enhancing their symbiotic efficiency. Moreover, the identification of quantitative trait loci (QTL) and candidate genes associated with symbiotic nitrogen fixation (SNF) in grain legumes provides valuable insights into the genetic basis of stress tolerance and its impact on symbiotic interactions (Dwivedi et al., 2015).

4.3 Co-evolution with legume hosts

The co-evolution of rhizobia and legume hosts involves intricate co-adaptation processes that enhance symbiotic efficiency. Rhizobial genetic elements, such as symbiotic plasmids, can be transferred among species and genera, leading to the emergence of symbiotic variants (symbiovars) that are adapted to specific legume hosts (Rogel et al., 2011). This lateral gene transfer facilitates the co-evolution of rhizobia and legumes, allowing for the development of highly specialized and efficient symbiotic relationships. The interplay between host genotype and environmental factors also influences the distribution and diversity of rhizobia, as seen in the Fynbos legumes of South Africa, where soil acidity and site elevation correlate with genetic variation in Mesorhizobium and Burkholderia (Lemaire et al., 2015).

The co-evolution of rhizobia and legume hosts has significant implications for symbiotic efficiency. The alignment of fitness between host and symbiont is essential for maintaining stable and effective mutualistic relationships (Friesen, 2012). Studies have shown that rhizobial inoculants based on native strains with high nitrogen fixation ability often perform better in the field due to their genetic adaptations to the local environment (Mendoza-Suárez et al., 2021). This highlights the importance of considering both host and Rhizobium genetics in breeding programs to enhance symbiotic nitrogen fixation and improve legume crop productivity (Dwivedi et al., 2015). The ongoing co-evolutionary processes between rhizobia and legumes continue to shape the genetic landscape of these symbiotic partners, driving the development of more efficient and resilient symbiotic interactions.

5 Practical Applications in Legume Crop Enhancement

5.1 Breeding for enhanced symbiosis

Marker-assisted selection (MAS) is a powerful tool in breeding programs aimed at enhancing the symbiotic relationship between legumes and Rhizobium. By identifying and selecting genetic markers associated with desirable traits such as high nitrogen fixation efficiency, nodulation competitiveness, and stress tolerance, breeders can develop legume varieties that form more effective symbioses with Rhizobium strains. This approach accelerates the breeding process and increases the likelihood of achieving superior legume-rhizobium partnerships (Lupwayi et al., 2006; Peña and Pueyo, 2011).

Incorporating symbiotic traits into breeding programs involves selecting legume genotypes that exhibit enhanced nodulation, nitrogen fixation, and tolerance to environmental stresses. By focusing on these traits, breeders can develop legume varieties that are better suited to form effective symbioses with Rhizobium strains, leading to improved crop yields and soil health. This approach also includes the use of biotechnological methods to introduce or enhance symbiotic traits in legume crops (Peña and Pueyo, 2011; Mabrouk et al., 2018).

5.2 Inoculant development and use

The production of Rhizobium inoculants involves selecting and cultivating Rhizobium strains with high nitrogen fixation potential, nodulation competitiveness, and environmental stress tolerance. These inoculants can be formulated in various carriers, such as peat, liquid, or granular forms, to ensure their viability and effectiveness when applied to legume crops. The development of high-quality inoculants is crucial for maximizing the benefits of rhizobium-legume symbiosis in agricultural systems (Lupwayi et al., 2006; Mendoza-Suárez et al., 2021).

Effective field application and management practices are essential for optimizing the performance of Rhizobium inoculants. This includes selecting the appropriate inoculant formulation, applying the correct inoculation rates, and ensuring favorable growing conditions for the legume crops. Additionally, practices such as soil inoculation, particularly with granular inoculants, have been shown to be more effective than seed inoculation in initiating nodulation and nitrogen fixation (Lupwayi et al., 2006; Mendoza-Suárez et al., 2021).

5.3 Integrated pest management

Rhizobium plays a significant role in enhancing plant health by promoting growth and providing protection against pathogens. Rhizobium strains can produce phytohormones, solubilize phosphates, and trigger systemic resistance in plants, thereby improving their overall health and resilience to pests and diseases. This makes Rhizobium an important component of integrated pest management (IPM) strategies in legume cultivation (Mabrouk et al., 2018; Fahde et al., 2023).

The interaction between Rhizobium and other beneficial microbes, such as mycorrhizal fungi and biocontrol agents, can further enhance plant health and productivity. These interactions can lead to improved nutrient uptake, enhanced stress tolerance, and increased resistance to pathogens. Understanding and harnessing these synergistic relationships can contribute to more effective IPM strategies and sustainable agricultural practices (Fahde et al., 2023).

5.4 Sustainable agriculture practices

The use of Rhizobium inoculants in legume cultivation can significantly reduce the need for chemical fertilizers by enhancing biological nitrogen fixation. This not only lowers production costs but also minimizes the environmental impact of chemical fertilizers, such as soil degradation and water pollution. By promoting the use of Rhizobium inoculants, farmers can adopt more sustainable and eco-friendly agricultural practices (diCenzo et al., 2018). Rhizobium-legume symbiosis contributes to soil health and fertility by improving soil structure, increasing organic matter content, and enhancing nutrient availability. The nitrogen fixed by Rhizobium is released into the soil through root exudates and decaying plant material (Rafique et al., 2021), enriching the soil with essential nutrients. This process not only benefits the current legume crop but also improves the soil for subsequent crops, promoting long-term soil fertility and sustainability (Lupwayi et al., 2006; Peña and Pueyo, 2011; Yates et al., 2021).

6 Case Studies and Field Trials

6.1 Success stories in different legume species

Soybeans have shown significant improvements in growth and yield when inoculated with specific strains of Rhizobium. For instance, a study demonstrated that co-inoculation with Rhizobium sp. SL42 and Bradyrhizobium japonicum 532C (Bj) resulted in higher shoot biomass and increased seed weight under salt stress conditions. This treatment improved grain yield by 7.4% and 8.1% under optimal conditions with Bj+SL48 and Bj+SL42+SL48 treatments, respectively (Ilangumaran et al., 2021). Another study highlighted that Rhizobium inoculation reduced the need for phosphorus and potassium fertilization in soybean-maize intercropping systems, enhancing nutrient uptake and overall plant health (Nyoki and Ndakidemi, 2018).

Chickpeas have also benefited from Rhizobium inoculation. In Spain, the co-inoculation of Mesorhizobium ciceri C-2/2 and Pseudomonas jessenii PS06 significantly increased seed yield by 52% compared to the control. This synergistic effect was particularly notable under field conditions, where the co-inoculation treatment also resulted in higher nodule fresh weight and shoot nitrogen content (Valverde et al., 2006).

Lentils have shown improved nodulation and plant growth when inoculated with pre-induced Rhizobium leguminosarum. The use of specific flavonoids like hesperetin and naringenin to pre-activate nod genes resulted in a significant increase in nodule number and dry matter accumulation in lentil plants (Begum et al., 2001; Igiehon et al., 2020). Additionally, Rhizobium sp. strain MRL3, which is tolerant to insecticides, improved the growth and yield of lentils in insecticide-stressed soils, demonstrating its potential as a bioinoculant (Ahemad and Khan, 2011; Buernor et al., 2022).

6.2 Experimental data from recent trials

Recent trials have employed various methodologies to assess the impact of Rhizobium inoculation on legume crops. For example, a field experiment in Ghana used a randomized complete block design to evaluate the effectiveness of different Rhizobium inoculants on soybean and cowpea. The results showed significant increases in nodule number, nodule dry weight, and grain yield for both crops when inoculated with specific strains like Biofix and BR 3 267 (Ulzen et al., 2016). Another study conducted greenhouse and field experiments to test the effects of single and dual inoculations on chickpea growth, finding that co-inoculation with Mesorhizobium ciceri C-2/2 and Pseudomonas jessenii PS06 yielded the highest seed yield and nodule fresh weight under field conditions (Valverde et al., 2006).

The impact of Rhizobium inoculation on yield and soil health has been profound. In soybeans, inoculation with Rhizobium sp. SL42 and Bradyrhizobium japonicum 532C not only increased grain yield but also improved nitrogen assimilation and the shoot K+/Na+ ratio, indicating enhanced stress tolerance and soil health (Ilangumaran et al., 2021). In chickpeas, the co-inoculation with Mesorhizobium ciceri C-2/2 and Pseudomonas jessenii PS06 led to higher nodule fresh weight and shoot nitrogen content, contributing to better soil fertility (Valverde et al., 2006). Similarly, in lentils, the use of insecticide-tolerant Rhizobium sp. strain MRL3 improved plant growth and yield in insecticide-stressed soils, suggesting a positive impact on soil microbial diversity and health (Ahemad and Khan, 2011). By integrating these findings, it is evident that Rhizobium inoculation plays a crucial role in enhancing legume crop performance and soil health, making it a valuable practice for sustainable agriculture.

7 Challenges and Future Directions

7.1 Overcoming biological and technical barriers

One of the primary challenges in utilizing Rhizobium for legume crop enhancement is the host range limitation. The specificity of rhizobium-legume symbiosis means that certain rhizobium strains can only nodulate specific legume species, which restricts the broader application of effective strains. For instance, the study on Rhizobium leguminosarum biovar viciae demonstrated that only 34% of isolates could nodulate Vicia faba, while 89% could nodulate local wild hosts, indicating a significant host range limitation (Mutch and Young, 2004). Additionally, the genetic diversity and specificity of Rhizobium strains further complicate the development of universal inoculants (Lemaire et al., 2015).

Environmental factors such as soil acidity, light availability, and geographical distribution also pose significant barriers to the effective use of Rhizobium inoculants. For example, variations in light availability can interactively determine plant growth and the effectiveness of Rhizobium strains, with higher light environments showing more pronounced differences in strain effectiveness (Heath et al., 2020). Soil acidity and site elevation have been shown to influence the genetic variation within Rhizobium populations, affecting their symbiotic efficiency (Lemaire et al., 2015). These environmental constraints necessitate the development of strains that are not only effective nitrogen fixers but also resilient to varying environmental conditions.

7.2 Future research priorities

To overcome the biological and technical barriers, advanced genetic engineering techniques are essential. Recent advances in host plant and Rhizobium genomics have identified several quantitative trait loci (QTL) and candidate genes associated with symbiotic nitrogen fixation (SNF) (Dwivedi et al., 2015). Genetic engineering can be employed to enhance these traits, creating Rhizobium strains with improved nodulation efficiency and broader host ranges. Synthetic biology approaches are also being explored to engineer new symbiotic interactions, potentially overcoming the host specificity issue (diCenzo et al., 2018).

Long-term ecological studies are crucial for understanding the persistence and effectiveness of Rhizobium inoculants in various agricultural settings. The competition between inoculant strains and native rhizobia often results in the failure of inoculants to establish and persist in the field (Mendoza-Suárez et al., 2021). Long-term studies can provide insights into the ecological dynamics of Rhizobium populations, helping to develop strategies for the sustainable use of inoculants. Additionally, these studies can identify environmental factors that influence the success of rhizobium-legume symbiosis, guiding the development of more resilient strains (Janczarek et al., 2015).

7.3 Policy and extension services

Policy plays a critical role in promoting the use of Rhizobium inoculants in sustainable agriculture. Government policies can incentivize the adoption of biofertilizers through subsidies, research funding, and regulatory support. Policies that promote the development and use of native Rhizobium strains, which are often more effective in local environments, can enhance the success of inoculant programs (Mendoza-Suárez et al., 2021). Additionally, international collaborations and knowledge-sharing platforms can accelerate the development and dissemination of effective Rhizobium technologies (Laranjo et al., 2014).

Farmer education and extension services are vital for the successful implementation of Rhizobium inoculants. Educating farmers about the benefits of Rhizobium inoculants, proper application techniques, and the importance of selecting appropriate strains can significantly improve adoption rates and effectiveness. Extension services can provide hands-on training, demonstrations, and ongoing support to ensure that farmers can effectively integrate Rhizobium inoculants into their farming practices (Dall’Agnol et al., 2014). By bridging the gap between research and practical application, extension services can play a pivotal role in enhancing legume crop productivity through Rhizobium symbiosis.

8 Concluding Remarks

Recent studies have provided significant genetic insights into the role of Rhizobium in legume crop enhancement. For instance, the identification of novel Rhizobium species such as Rhizobium paranaense, which is effective in nodulating and fixing nitrogen with common bean, highlights the genetic diversity and potential of these bacteria in agricultural applications. Additionally, the genetic diversity and distribution of rhizobia associated with medicinal legumes have been shown to be influenced by soil fertility, indicating that different rhizobial species adapt to varying soil conditions. The complex molecular dialogue between legumes and rhizobia, involving various signal molecules and cell-surface components, further underscores the genetic intricacies of this symbiotic relationship. The practical applications of Rhizobium in legume crop enhancement are vast and promising. Co-inoculation of Rhizobium with plant growth-promoting rhizobacteria (PGPR) has been shown to significantly improve nodulation, plant growth, and nitrogen fixation in common beans, demonstrating a synergistic effect that can be harnessed for better crop yields. Moreover, the use of Rhizobium as a biofertilizer for non-leguminous crops like tomatoes and peppers has been explored, showing potential for broader agricultural applications. The role of Rhizobium in enhancing abiotic stress tolerance through mechanisms such as trehalose accumulation also presents practical benefits for crop resilience under adverse conditions.

The integration of Rhizobium and PGPR in legume cultivation can lead to substantial improvements in agricultural productivity. Enhanced nodulation and nitrogen fixation directly contribute to better plant growth and higher yields, as evidenced by studies on common beans and other legumes. The ability of Rhizobium to compete effectively with native strains and persist in the field further ensures sustained benefits over multiple growing seasons. Additionally, the genetic adaptation of native rhizobial strains to local environments can be leveraged to develop more effective inoculants, tailored to specific agricultural contexts. The use of Rhizobium in legume cultivation promotes environmental sustainability by reducing the reliance on chemical fertilizers. Biological nitrogen fixation by rhizobium-legume symbioses is an eco-friendly alternative that enhances soil fertility and reduces the environmental impact of agricultural practices. Furthermore, the ability of Rhizobium to form symbiotic relationships with a variety of legumes and even some non-leguminous crops expands its potential for sustainable agriculture. The role of Rhizobium in improving plant resilience to abiotic stresses also contributes to more sustainable crop production under changing climatic conditions.

The role of Rhizobium in legume crop enhancement is multifaceted, encompassing genetic diversity, practical applications, and significant implications for agricultural productivity and environmental sustainability. Future research should focus on field trials to validate the effectiveness of co-inoculation strategies and the use of native rhizobial strains in diverse agricultural settings. Additionally, exploring the molecular mechanisms underlying rhizobium-legume interactions can provide deeper insights into optimizing these symbiotic relationships for enhanced crop performance. Overall, the integration of Rhizobium into sustainable agricultural practices holds great promise for improving legume production and contributing to global food security.

Acknowledgments

The authors sincerely thank the two anonymous peer reviewers for their valuable comments and suggestions on the manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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