Selection of competitive and effective rhizobial strain for enhanced chickpea production under Indo-Gangetic plains of India.

Chickpea (Cicer arietinum L.) is a vital legume crop, but its productivity is often limited by poor soil fertility. This study aimed to assess the nodulation efficacy and plant growth-enhancing activities of six Mesorhizobium spp. strains in the chickpea cultivar Pusa 362 through the Leonard jar experiment and field trial. The strains, including two strains from ICRISAT (reference strains), were tested for solubilization of phosphate, potassium, and zinc, and production of Indole-3-Acetic Acid (IAA). Strain C5 excelled in phosphate solubilization (61.40 µg/ml), while C7 was superior in potassium (26.10 µg/ml) and zinc phosphate (69.15 µg/ml) solubilization; C17 showed the highest IAA production (25.75 µg/ml). In the Leonard jar experiment, inoculation of strains M. ciceri C5 and M. helmanticense C17 exhibited the highest nodule number and root dry weight, while treatments with M. ciceri C5 and M. helmanticense C7 inoculation recorded the maximum nodule dry weight and shoot dry weight. Field trials indicated significant improvements in nodulation, biomass, and nitrogen content in chickpeas inoculated with these strains. Treatment with strain C7 led to the highest increase in nodule number and root dry weight over the control, while strain C5 inoculation recorded maximum grain yield. Correlation analysis showed positive relationships between yield and several growth parameters. Nodule occupancy tests revealed that strain C7 had the highest occupancy (32.98%), followed by C5 (31.92%), indicating superior nodulation competitiveness under field conditions. These results suggest that inoculation with specific Mesorhizobium strains can significantly enhance chickpea productivity through improved nodulation and nitrogen fixation.