Author(s): DPavan Kumar Agrawal, Shruti Agrawal
Plant growth promoting rhizobacteria (PGPR) influence the plant growth by various direct or indirect mechanisms. To look for efficient PGPR strains having multiple activities, total 28 bacterial isolates were isolated from different rhizospheric soil of tomato crop in the vicinity of Dehradun. The bacterial isolates were biochemically characterized and screened in vitro for their plant growth promoting traits like production of indole acetic acid (IAA), phosphate solubilization, hydrogen cyanide (HCN), siderophore and catalase. Total 5 bacterial isolates of Bacillus showed potential PGPR activities. The productions of indole acetic acid (IAA) by all rhizobacteria were investigated as important mechanism for plant growth stimulation. All rhizobacterial isolates produced IAA in vitro by the addition of L-tryptophan, in the culture medium. All rhizobacterial isolates in comparison with the control, also showed increment in both the shoot and the roots of tomato seedlings. PGPR were tested for seed germination and seedling vigour by using tomato seeds in roll towel method. Generally, the seed germination ranged from 90 percent (uninoculated control) to 97.5 percent. All the strains, HBS-VIII, FAR-IIIb, HBR-II, GAR-III and HBR-VII significantly improved seed germination when compared to the uninoculated control (UIC). The isolate HBRVII showed significantly increased seed germination (97.5%) and also shoot and root length as well as enhanced vigour index of 115.50, 714.35 after 6 and 16 days respectively. The rhizobacteria could exhibit more than two or three PGPR traits that promote plant growth directly or indirectly.