Abstract

Cold-tolerant plant growth-promoting rhizobacteria (PGPR) are of immense agronomic importance due to the fact that the winter season crop growing cycle is subject to varying spells of low temperatures and such PGPRs are metabolically functional at cold conditions. Thirty-five (35) rhizobacterial isolates were isolated from lentil rhizospheric soil, six isolates showing maximum exponential growth at both 10 and 15°C after 24 h were selected and characterized belonging to genera Bacillus and Pseudomonas. Production of indole acetic acid (IAA) ranged from 12.7-17.5 µgml^-1 at 10°C to 18.4-20.4 μg/ml at 15°C. At 15°C, an isolate J-17 was found to be strong HCN producer whereas at 10°C, only two isolates: J-26 and J-30 were moderate producers. P-solubilizion at 15°C, ranged from 62.5 - 77.2 µgml^-1. However, at 10°C none of the isolates solubilized P. At 15°C, catechol type siderophore production ranged from 523.4 - 606.1 µgml^-1. On the basis of the PGP traits, four isolates J-3, J-17, J-18 and J-30 were selected for evaluation under field conditions of lentil at research farm of PAU, Ludhiana, Punjab, India. Coinoculation exhibited a significant increase in nodule number, nodule dry weight, plant and root dry weight, chlorophyll and leghaemoglobin content over Rhizobium alone. Application of J-3, J-17, J-18 and J-30 along with Rhizobium further enhanced the grain yield (1.8, 4.4, 3 and 1.4%).

Key words: HCN production, indole acetic acid, siderophore, P-solubilization.