Cluster bean was selected as the host plant for this experiment. The seeds of cluster bean were surface sterilized with 0.2% mercuric chloride (HgCl2) solution for 2 min and then pretreated with standard rhizobial inoculum (i.e. Bradyrhizobium sp. (cluster bean) procured from Department of Microbiology, CCS Haryana Agricultural University, India) used as a basal dose.