Isolation and characterization of indole acetic acid (IAA) producing Klebsiella pneumoniae strains from rhizosphere of wheat (Triticum aestivum) and their effect on plant growth.

The present study was undertaken for isolation of Klebsiella strains from rhizosphere of wheat (T. aestivum), screening and characterization of these strains for in vitro indole acetic acid (IAA) production and studying the effect of these strains on plant growth under gnotobiotic conditions. Nine strains of Klebsiella were isolated from rhizosphere of wheat (var. Lokwan) and identified as K. pneumoniae by 16S rRNA gene sequencing. Six K. pneumoniae strains showed in vitro IAA production. Colorimetric analysis showed that K8 produced maximum IAA (27.5 mg l(-1)) in the presence of tryptophan (1 mg ml(-1)) at 72 h of incubation with optimum conditions as pH 8.0, 37 degrees C and 0.5% (w/v) NaCl concentration. GC-MS analysis and IR studies confirmed presence of IAA in the cell filtrates of strain K8. Effect of six IAA producing Klebsiella strains on plant growth was studied by performing series of seed germination tests using moth bean seeds under axenic conditions and pot experiments using sterilized soil and wheat seeds (var. Lokwan). Strain K11 and K42 demonstrated increase in root length of inoculated moth beans (approximately 92.71% over the control). Results of pot experiments indicated that almost all the six IAA producing Klebsiella strains significantly increased the root length and shoot height of inoculated wheat seedlings over the control. The results suggest that these are promising isolates from wheat rhizosphere and merits research on appliance of these strains in agriculture.