Legume Genomics and Genetics 2024, Vol.15, No.4, 163-175 http://cropscipublisher.com/index.php/lgg 171 by enriching the soil with essential nutrients (Liu et al., 2018; Raza et al., 2020; Cui et al., 2021). The ability of legumes to fix nitrogen biologically makes them an integral part of sustainable agricultural practices, promoting long-term soil fertility and reducing the environmental impact of synthetic fertilizers. Incorporating nitrogen-fixing legumes into crop rotation and intercropping systems can significantly enhance soil fertility and crop yields. Legumes, when used in rotation with non-leguminous crops, replenish soil nitrogen levels, thereby reducing the dependency on chemical fertilizers. This practice not only improves soil structure and fertility but also helps in breaking pest and disease cycles, leading to healthier crops (Liu et al., 2018; Raza et al., 2020). Intercropping legumes with other crops can also provide mutual benefits, such as improved nutrient availability and better pest management, contributing to more resilient and productive agricultural systems (Cui et al., 2021). 6.2 Environmental benefits of reduced nitrogen fertilizer use The use of nitrogen-fixing legumes in agriculture can lead to a significant reduction in greenhouse gas emissions. Chemical nitrogen fertilizers are a major source of nitrous oxide, a potent greenhouse gas. By reducing the need for these fertilizers, biological nitrogen fixation helps mitigate the release of nitrous oxide into the atmosphere, thereby contributing to climate change mitigation (Ibañez et al., 2016; Raza et al., 2020). The adoption of legume-based cropping systems can thus play a vital role in reducing the carbon footprint of agricultural practices (Jach et al., 2022). Excessive use of chemical fertilizers often leads to nutrient runoff, causing water pollution and eutrophication in aquatic ecosystems. Nitrogen-fixing legumes help mitigate this issue by naturally enriching the soil with nitrogen, reducing the need for synthetic fertilizers and consequently decreasing the risk of nutrient leaching into water bodies (Raza et al., 2020; Jach et al., 2022). This environmentally friendly approach not only protects water quality but also supports the health of aquatic ecosystems and biodiversity (Ibañez et al., 2016). 6.3 Challenges and future directions Climate change poses significant challenges to the effectiveness of nitrogen-fixing symbiosis in Fabaceae. Changes in temperature, precipitation patterns, and soil conditions can affect the symbiotic relationship between legumes and rhizobia, potentially reducing the efficiency of nitrogen fixation. Future research should focus on understanding the impacts of climate change on this symbiosis and developing strategies to enhance the resilience of legume-rhizobia interactions under changing environmental conditions (Lipa and Janczarek, 2020; Cui et al., 2021). This may include breeding climate-resilient legume varieties and exploring the use of stress-tolerant rhizobial strains (Ficano et al., 2021). Advancements in molecular biology and genomics offer new opportunities to enhance the efficiency of nitrogen-fixing symbiosis in Fabaceae. Future research should aim to identify and manipulate key genetic and regulatory pathways involved in nitrogen fixation to improve symbiotic efficiency and compatibility between legumes and rhizobia (Zhao et al., 2021). Additionally, exploring the potential of engineering nitrogen-fixing capabilities into non-leguminous crops, such as cereals, could revolutionize agricultural practices and reduce the reliance on chemical fertilizers (Delaux et al., 2015). Continued research and technological innovations in this field are essential for developing sustainable and resilient agricultural systems that can meet the growing global food demand while minimizing environmental impacts (Cui et al., 2021). 7 Concluding Remarks The study on the molecular mechanisms of nitrogen-fixing symbiosis in Fabaceae has elucidated several critical insights. Firstly, the phylogenetic analyses have revealed a highly resolved phylogeny of Fabaceae, supporting numerous polyploidization events and providing a foundation for understanding the evolutionary history of rhizobial nitrogen-fixing symbiosis. Additionally, the study of genomic traces has highlighted the fragility and evolutionary susceptibility of nitrogen-fixing symbiosis, with multiple independent losses observed across different species. The diversity and phylogenetic patterns of symbiotic genes in Paraburkholderia and Bradyrhizobiumspecies have been mapped, revealing horizontal gene transfer events and the existence of distinct
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