Molecular Soil Biology 2024, Vol.15, No.3, 129-139 http://bioscipublisher.com/index.php/msb 134 for Rhizobium. However, competition with native rhizobia and other soil bacteria can reduce the effectiveness of introduced Rhizobiumstrains. Native strains often outcompete inoculant strains for nodule occupancy, which can lead to lower nitrogen fixation rates if the native strains are less efficient (Mendoza-Suárez et al., 2021). Understanding the interactions between Rhizobium and other soil microorganisms is essential for improving symbiotic efficiency. 5.3 Agricultural practices (e.g., crop rotation, use of cover crops) Agricultural practices such as crop rotation and the use of cover crops can significantly influence Rhizobium efficiency (Goyal et al., 2021). Crop rotation, especially with legumes, can enhance soil nitrogen levels and improve the overall health of the soil microbiome, creating a more conducive environment for Rhizobium(Fustec et al., 2011). The use of cover crops can also benefit Rhizobium by preventing soil erosion, improving soil structure, and maintaining soil moisture levels. These practices help sustain a healthy population of Rhizobiumand other beneficial microorganisms, thereby enhancing nitrogen fixation efficiency. 5.4 Genetic factors in bothRhizobiumand legume hosts Genetic factors in both Rhizobium and their legume hosts play a crucial role in determining the efficiency of nitrogen fixation. The genetic compatibility between specific Rhizobium strains and legume varieties can significantly impact the success of the symbiotic relationship (Pankievicz et al., 2019). Advances in genomics have identified several quantitative trait loci (QTL) and candidate genes associated with symbiotic efficiency in both Rhizobium and legumes (Dwivedi et al., 2015). Breeding programs that focus on improving these genetic traits in both partners can lead to the development of high-yielding, nitrogen-efficient legume cultivars. Additionally, genetic engineering and the use of stress-tolerant Rhizobium strains can further enhance nitrogen fixation under adverse environmental conditions. 6 Advances inRhizobiumInoculant Technology 6.1 Development and application of commercial Rhizobiuminoculants The development and application of commercial Rhizobiuminoculants have significantly advanced over the years, driven by the need to enhance nitrogen fixation and improve crop yields. For instance, the use of peat carrier-based inoculants has been shown to significantly enhance nodulation, nitrogen fixation, and nutrient uptake in Vicia faba L. (Allito et al., 2020). Similarly, the formulation of inoculants based on autochthonous strains, such as Rhizobium leguminosarumbv. phaseoli LCS0306, has demonstrated superior performance in nitrogen fixation and grain yield in common beans, especially when combined with carriers like perlite and biochar (Table 1) (Pastor-Bueis et al., 2019). These advancements underscore the importance of selecting effective rhizobial strains and appropriate carriers to maximize the benefits of inoculation. Table 1 Nodulation and nitrogen symbiotic fixation indicators for the combined analysis of 2017 and 2018 and inoculant treatments in field trial (Adopted from Pastor-Bueis et al., 2019) Inoculation treatment Number of nodules per plant Nodule biomass (dry) (g per plant) Aerial biomass (dry) (kg/ha) Aerial biomass N (%) Ndfa (%) Negative control 36.8a 0.647a 3428a 2.45a 41.3ab ReCFN42T (perlite) 37.7a 1.002b 5131bc 2.50a 43.3ab Rp ATCC 14482T (perite) 29.0a 1.154bc 4911b 2.53a 46.6bc N ferilized non-inoculated control 34.0a 0.512a 5328bc 2.35a 39.2a RIp LCS0306 (perlite) 38.3a 1.230C 5592C 2.58a 50.0C Note: The table contains the mean values for the following treatments: inoculation with the autochthonous strain Rhizobium leguminosarumbv. phaseoli LCS0306, the type strains of Rhizobium eti (Re CFN42T) and Rhizobium phaseoli (Rp ATCC 14482T), and the two non-inoculated controls (non-fertilized and N-fertilized). Data followed by the same letter did not significantly differ at p<0.05 in the LSD test (Adopted from Pastor-Bueis et al., 2019) 6.2 Methods for enhancing inoculant efficiency and effectiveness Several methods have been explored to enhance the efficiency and effectiveness of Rhizobium inoculants. One approach involves the combined inoculation with arbuscular mycorrhizal fungi (AMF) and rhizobia, which has
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