Molecular Soil Biology 2024, Vol.15, No.3, 129-139 http://bioscipublisher.com/index.php/msb 133 Figure 2 The histogram shows the evaluation of phenolic compounds and various oxidative stress markers in faba bean plants under the Bean yellow mosaic virus (BYMV) challenge (Adopted from Abdelkhalek et al., 2022) Image caption: (A) total phenolic compounds, (B) free radical quenching activity (DPPH), (C) hydrogen peroxides (H2O2), and (D) malondialdehyde (MDA). All compounds were evaluated in the treatment groups: G1: control plants, G2: BYMV-infected plants, G3: plants of soil treated with a Rhizobium isolate 4 days before BYMV inoculation, G4: plants treated by foliar spraying of culture filtrate, 24 h before inoculation with BYMV. The columns reflect the mean of five biological replicates, while the bars represent the standard deviation (±SD). Columns with the same letter meaning do not differ significantly (Adopted from Abdelkhalek et al., 2022) 4.3 Adaptations of Rhizobiumto various environmental conditions Rhizobiumstrains exhibit remarkable adaptations to diverse environmental conditions, which can influence their effectiveness in nitrogen fixation (Wang et al., 2018b). For instance, Cupriavidus taiwanensis strains isolated from heavy metal-rich soils in New Caledonia showed various tolerances to metals like Ni, Zn, and Cr, suggesting their adaptation to these specific environments. Moreover, the co-inoculation of Rhizobium with plant growth-promoting rhizobacteria (PGPR) such as Bacillus megateriumhas been shown to enhance nodulation and growth of common beans in low phosphorus soils, indicating that Rhizobiumcan work synergistically with other soil microbes to improve plant health under nutrient-limited conditions (Korir et al., 2017; Jach et al., 2022). These findings underscore the importance of understanding the diversity, specific interactions, and environmental adaptations of Rhizobiumstrains to optimize their use in sustainable agriculture and soil health improvement. 5 Factors InfluencingRhizobiumEfficiency 5.1 Soil pH, temperature, and moisture The efficiency of Rhizobiumin nitrogen fixation is significantly influenced by soil pH, temperature, and moisture. Optimal soil pH is crucial as it affects the availability of nutrients and the survival of Rhizobium. Acidic or highly alkaline soils can hinder the growth and activity of these bacteria, thereby reducing nitrogen fixation efficiency (Allito et al., 2020). Temperature also plays a vital role; extreme temperatures can lead to protein denaturation and nucleic acid damage in Rhizobium, affecting their ability to fix nitrogen (Owaresat et al., 2023). Soil moisture is another critical factor, as both drought and waterlogging can adversely impact Rhizobiumactivity and symbiotic efficiency. 5.2 Presence of other soil microorganisms The presence of other soil microorganisms can either enhance or inhibit the efficiency of Rhizobium. Beneficial microorganisms, such as mycorrhizal fungi, can improve nutrient uptake and create a more favorable environment
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