ISOLATION AND IDENTIFICATION OF CHROMIUM TOLERANT BACTERIAL STRAINS AND THEIR POTENTIAL TO PROMOTE PLANT GROWTH

Abstract

Chromium (Cr) presence in soil higher than the permissible limit and its uptake in plants results in reduced growth and yield. The current study was thus aimed at the isolation and identification of chromium-tolerant bacterial strains and to evaluate their potential in improving edible plant growth. Four soil samples from Gujrat District, Pakistan, were collected and analyzed for Cr content. Thirteen bacterial colonies were isolated from the sample with highest chromium content. Tests were performed with the isolates to check chromium tolerance and plant growth-promoting (PGP) abilities; indole acetic acid production and phosphate solubilization, in in vitro. The tolerant isolates which also exhibited PGP abilities were used as inoculants in germination and pot trial experiment with spinach plant. The isolates A5, identified as Pseudomonas plecoglossicida, and A6, identified as Staphylococci saprophyticus through 16S rRNA gene sequencing, were found to be tolerant up to 700 mg/L of Cr (VI). They were both effective in solubilizing phosphate but only A5 (Pseudomonas plecoglossicida) was able to produce indole acetic acid. A5 also increased the percentage of seed germination by 17 to 46% and also increased spinach plant’s biomass by 44% with respect to the control. Keeping in view the effects on spinach germination and pot experiments, A5 (Pseudomonas sp.) can be developed as a bio-inoculant for agricultural applications and may potentially be useful for bioremediation of Cr using plants.