Isolation, identification and molecular characterization of Fluorescent Pseudomonads from the rhizosphere

Agrochemicals are widely used for plant disease control, but they leave toxic residues in agricultural commodities. Biological control plays an important role in sustainable disease management. Among biocontrol agents, Plant Growth Promoting Rhizobacteria (PGPR) are an important alternative, particularly Fluorescent Pseudomonads, which promote plant growth and aid in disease management. Bacterial antagonist belonging to Pseudomonas spp. are well-documented for their antagonistic abilities against various diseases across diverse pathosystems. Three Pseudomonas species are fluorescent, namely P. aeruginosa, P. fluorescens and P. putida. P. aeruginosa, the type species of the genus Pseudomonas, exhibits greater uniformity due to fewer biotypes compared to other fluorescent pseudomonads. Since P. aeruginosa is a human pathogen, distinguishing it from P. fluorescens is essential. The identification and diversity of fluorescent pseudomonad (FLP) isolates were investigated using the 16S rRNA gene sequence. PCR was performed to amplify the 16S rRNA gene using primers 27F/1492R. Amplified DNA products were sequenced and analyzed using BLASTn (NCBI database) for species identification. Ten native FLP isolates were obtained. Nine of the ten isolates showed high bootstrap support value to P. aeruginosa and and one to P. fluorescens. Significant diversity was observed among isolates, as evidenced by a phylogenetic dendrogram constructed using CLUSTAL W.