Symbiotic Effectiveness of Indigenous Rhizobial Strains Isolated from Soybean Cultivars under Chhattisgarh Agro-Climatic Conditions

Soybean (Glycine max L. Merrill) is a major legume crop and its productivity relies mainly on symbiotic nitrogen fixation with rhizobia. Biological nitrogen fixation (BNF) through symbiosis with rhizobia plays a crucial role in reducing dependence on chemical fertilizers, enhancing soil fertility, and sustaining crop productivity. The current study assessed the nodulation and symbiotic efficacy of native rhizobial strains isolated from soybean cultivars grown under the agroclimatic region of Chhattisgarh. Symbiotic parameters like nodulation characteristics, biomass accumulation, shoot nitrogen content and leghaemoglobin concentration were measured at 50% flowering stage. Field trials with seven soybean cultivars (SNM-24-68, SNM-24-69, SNM-24-70, SNM-24-71, SNM-24-72, SNM-24-73, SNM-24-74) assessed for growth parameters and symbiotic traits at 60 DAS. SNM-24-74 performed best, showing maximum plant height (66.75 cm), nitrogen uptake (122.75 mg/plant), nodule number (80.75/plant), and leghaemoglobin (2.70 mg/g). Nodulation assessments revealed that SNM-24-74 recorded the highest dry nodule weight (722.00 mg/plant). There was a noticeable difference between cultivars being the significantly highest in Variety, SNM-24-74 followed by SNM-24-70. Seven rhizobial isolates SR-68, SR-69, SR-70, SR-71, SR-72, SR-73, SR-74 were isolated from these seven soybean cultivars and coded according to the concerned cultivars. Further, among native rhizobial strains, SR-74 and SR-70 isolated from soybean cultivars SNM-24-74 and SNM-24-70 respectively, showed good colony growth on YEMA media and all showed a positive response towards IAA production. The study suggests that indigenous rhizobial isolates associated with high-performing cultivars such as SNM-24-74 could be further explored as potential bioinoculants for enhancing soybean productivity in Chhattisgarh, India.