Evaluation of plant growth promoting traits of thermotolerant rhizobacteria from mungbean rhizosphere

Plant growth promoting rhizobacterial (PGPR) colonize the root and enhance plant growth through multifarious activities. A total of 20 rhizobacterial isolates were isolated at 35 and 40°C from 12 soil samples taken from different locations of mungbean rhizospheric soil. Five isolates showing maximum growth at 35° and 40° C were selected and characterized and found as belonging to genera Bacillus and Rhizobium. IAA production ranged from 0.35–17.08 ìg/ml and 0.70–31.32 ìg/ml in the presence of tryptophan at 35° and 40°C respectively. Isolates S-11 and R-6 were found to be strong producer of HCN at 40°C. Maximum siderophore production was observed with isolate R-6 at 35 and 40°C as evident by the halo on CAS agar and highest catechol type siderophores was produced by R-6 (72.37 μg/ml) followed by S-11 (72.27 μg/ml) at 40°C. Catechol type siderophore at 35°C byR-6(71.88μg/ml) was higher incomparis on to S-11(63.08 μg/ml.). Potent isolates were found to produce flavonoidlike compounds and exhibited biofilm formation.