Diversity analysis of pseudomonas in rice rhizosphere for multifaceted plant growth promotion

This investigation was carried out based on the hypothesis that there may be some pseudomonad strains, which could exist in rhizosphere of plant species contributing multifaceted beneficial activities. For this purpose, 21 pseudomonad isolates from the rhizosphere of rice, cultivated in western parts of Tamil Nadu were screened. All the 21 isolates were authenticated as pseudomonads by a genus-specific PCR screening. The molecular diversity of these isolates was investigated by Amplified Ribosomal DNA Restriction Analysis (ARDRA) and the dendrogram obtained from the analysis revealed that all the 21 isolates clustered into seven groups. Further, these isolates were screened for plant growth promoting activities such as diazotrophy (PCR amplification of nifH gene and acetylene reduction assay), Indole acetic acid (IAA) and siderophore production (spectrometrically), 1-Aminocyclopropane-1-carboxylic acid (ACC) deaminase for ethylene regulation (PCR screening), mineral solubilization (biochemically) and antagonistic potential against soil pathogenic fungi (dual culture assay). Based on the results, two elite Pseudomonas isolates (S9 and O3) were chosen as multi-functional plant growth-promoting rhizobacteria, paving way for potential use as bioinoculants in rice.