Molecular Microbiology Research 2024, Vol.14, No.2, 109-118 http://microbescipublisher.com/index.php/mmr 115 Figure 2 Roots of G. max cv. Enrei inoculated with the rhizobial strains. The soybeans were grown in the presence of 0 (A–D), 5 (E–H), 12.5 (I–L) and 20 mM (M–P) of potassium nitrate, respectively. The Enrei roots and nodule sections were photographed at 30 dpi. Scale bars: 1 cm (Adopted from Nguyen et al., 2019) Image caption: The figure compares the nodulation effects of the traditional rhizobial strain USDA110 with three novel rhizobial strains (NKS4, NKM2, NKTG2). The results indicate that USDA110 is almost unable to form effective nodules under high nitrate conditions (especially at 12.5 mM and 20 mM), whereas the novel strains can still produce larger and heme-rich pink nodules under these conditions, demonstrating their superior nodulation capability in high nitrate environments (Adapted from Nguyen et al., 2019) Moreover, the application of rhizobia in metal-contaminated and high saline lands has been shown to improve crop yield and soil health, further underscoring their role in sustainable agriculture (Bellabarba et al., 2019). By leveraging the symbiotic relationship between rhizobia and legumes, farmers can enhance soil fertility, reduce dependency on chemical fertilizers, and promote environmentally friendly farming practices (Lindström and Mousavi, 2019; Thompson and Lamp, 2021). 7 Technological and Environmental Considerations 7.1 Genetic engineering of rhizobia Genetic engineering of rhizobia has emerged as a promising approach to enhance the efficiency of symbiotic nitrogen fixation (SNF) and improve legume growth. Advances in molecular biology have enabled the modification of rhizobial strains to increase their tolerance to abiotic stresses such as extreme temperatures, pH, salinity, and drought, which are critical for maintaining effective nitrogen fixation under varying environmental conditions (Mabrouk et al., 2018; Owaresat et al., 2023). Additionally, genetic modifications have been aimed at improving the nodulation process and nitrogen fixation efficiency even in the presence of high nitrate concentrations, which typically inhibit these processes (Nguyen et al., 2019). The development of SNF-efficient rhizobial species tailored to the genetic makeup of specific legume hosts has shown potential in enhancing the overall productivity and sustainability of legume crops (Goyal et al., 2021).
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