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Three strains of Gram‐negative bacterium, Rhizobium, were developed by gamma (γ)‐irradiation random mutagenesis. The developed strains were evaluated for their augmented features for symbiotic association, nitrogen fixation, and crop yield ofthree leguminous plants—chickpea, field‐pea, and lentil—in agricultural fields of the northern Indian state of Haryana. Crops treated with developed mutants exhibited significant improvement in plant features and the yield of crops when compared tothe control‐uninoculated crops and crops grown with indigenous or commercial crop‐specific strains of Rhizobium. This improvement was attributed to generated mutants, MbPrRz1 (on chickpea), MbPrRz2 (on lentil), and MbPrRz3 (on field‐pea). Additionally, the cocultured symbiotic response of MbPrRz1 and MbPrRz2 mutants was found to be more pronounced on allthree crops. The statistical analysis using Pearson's correlation coefficients revealed that nodulation and plant biomass were the most related parameters of crop yield. Among the effectiveness of developed mutants, MbPrRz1 yielded the best results for allthree tested crops. Moreover, the developed mutants enhanced macro‐ and micronutrients of the experimental fields whencompared with fields harboring the indigenous rhizobial community. These developed mutants were further genetically characterized, predominantly expressing nitrogen fixation marker, nifH, and appeared to belong to Mesorhizobium ciceri (MbPrRz1) and Rhizobium leguminosarum (both MbPrRz2 and MbPrRz3). In summary, this study highlights the potential ofdeveloped Rhizobium mutants as effective biofertilizers for sustainable agriculture, showcasing their ability to enhancesymbiotic relationships, crop yield, and soil fertility.