Potential of Azotobacter vinelandii Khsr1 as bio-inoculant
The present study deals with the isolation and characterization of Azotobacter vinelandii Khsr1 from roots of the weed, Chrysopogon aucheri, commonly known as golden beard grass indigenous to Khewra salt range, Pakistan and its evaluation as bio-inoculant. The population of the isolate varied from 107 to 108 cfu/g fresh weight of root. The preliminary identification of the isolate was made on the basis of carbon/nitrogen source utilization pattern as revealed by QTS-24 miniaturized identification system test which placed the isolate to the genus Azotobacter. The 16S-rRNA partial sequence analysis confirmed the isolate as A. vinelandii strain Khsr1. The 556 long nucleotide sequence of the isolate showed 98% similarity with A. vinelandii DJ (accession no. 012560.1). The isolate was capable of producing phytohormones: indole-3-acetic acid, gibberellic acid, trans-zeatin riboside and abscisic acid in culture supernatant, stimulated growth of Zea mays L. seedlings and augmented proline content of roots and shoots both under normal and NaCl stressed conditions. However, the magnitude of stimulation is higher under un-stressed condition.
Key words: Azotobacter vinelandii Khsr1, phytohormones production, growth stimulation, salinity stress.