Phosphate Solubilizing Bacteria (PSB) isolated from the crops grown in vertisols were tested for the production of Plant Growth Promoting Substances (PGPS) such as Indole Acetic Acid (IAA), Gibberellic Acid (GA) and organic acids. All the 30 isolates of PSB were able to produce both IAA and GA and the amount ranged from 1.1 to 28.0 Âµg/25 and from 0.6 Âµg to 9.8 Âµg/25 mL of broth, respectively. The strains PSBV-4 and PSBV-5 produced the maximum amounts of IAA and GA, respectively. The organic acids produced were gluconic acid, tartaric acid, citric acid, maleic acid, succinic acid, glyoxalic acid and a few unidentified acids. The strain PSBV-9 and the standard Pseudomonas striata produced six organic acids while strains PSBV-10, PSBV-25 and PSBV-16 produced only five organic acids. Hierarchical cluster analysis was used to separate PSBs according to IAA and GA production and the PSBs were classified into three major groups. Correspondence analysis was used to find any association between PSB isolates and organic acid production and it showed a significant association between organic acid production and PSB isolates. The PSB strains isolated here have the potential to promote plant growth, as demonstrated here based on the production of PGPS and organic acids. However, their ability to promote plant growth under greenhouse and field conditions has to be validated.
A. Vikram, H. Hamzehzarghani , A.R. Alagawadi , P.U. Krishnaraj and B.S. Chandrashekar , 2007. Production of Plant Growth Promoting Substances by Phosphate Solubilizing Bacteria Isolated from Vertisols. Journal of Plant Sciences, 2: 326-333.