Isolation of phytohormones producing plant growth promoting rhizobacteria from weeds growing in Khewra salt range, Pakistan and their implication in providing salt tolerance to Glycine max L.

Abstract

Present investigation was made to isolate and characterize plant growth promoting rhizobacteria (Rkh1 - Rkh4) from rhizosphere of four weeds: Chrysopogon aucheri,Lactuca dissecta, Solanum surratense and Sonchus arvensis thriving under high salinity (EC: 2.3 dS/m) of Khewra salt range and the results were compared with strain Rak isolated from rhizosphere (EC: 0.2 dS/m) of Solanum surratense grown in arid area of district Attock. The tolerance of all the strains was checked against the salt present in culture media in the form of rhizospheric soil filtrate of weeds collected from Khewra salt range. The nutrient contents of rhizospheric soil of weeds were measured. All the strains were capable to produce phytohormones indole-3-acetic acid (IAA), gibberellic acid (GA3), trans-zeatin riboside (t-zr) and abscisic acid (ABA) in the culture media. Inoculation of strains on soybean seedlings treated with or without 20 dS/m NaCl resulted in better growth and higher proline contents than control plants. The strains isolated from weeds of Khewra salt range particularly Rkh3 appears more promising for potential biofertilizers in saline fields. Key words: Plant growth promoting rhizobacteria, nutrient contents, salt tolerance, phytohormones production, proline contents.