isolation and characterization of growth-promoting bacteria from rhizosphere of thymus danenensis and study of their potential for enhancement of seed germination

the iranian thymus daenensis subsp. daenensis is rich in monoterpene phenols (especially thymol and carvacrol). this research was conducted to isolate and characterize the plant growth promoting rhizobacteria (pgprs) from rhizosphere of t. daenensis. pgprs were screened based on some physiological traits including iaa production, phosphate solubilization, and siderophore compounds production abilities, and also seed germination and vigor tests. twenty one rhizobacteria were isolated from the rhizosphere samples of t. daenensis which grow widely in iran, and their effect on seed germination properties was studied in a completely randomized block design with three replications. we could characterize four isolates for pgprs activity based on physiological and germination assays. tde3, tde16 and tde20 isolates had the phosphate solubilization and siderophores production abilities. tde4 (achromobacter spiritinus) was the only isolated bacteria which significantly improved the sgr and vi of t. daenensis seeds. these four isolates have the potential to be used as pgprs in cultivation of t. daenensis.